/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* Task-based RCU implementations.
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*
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* Copyright (C) 2020 Paul E. McKenney
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*/
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#ifdef CONFIG_TASKS_RCU_GENERIC
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////////////////////////////////////////////////////////////////////////
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//
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// Generic data structures.
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struct rcu_tasks;
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typedef void (*rcu_tasks_gp_func_t)(struct rcu_tasks *rtp);
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typedef void (*pregp_func_t)(void);
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typedef void (*pertask_func_t)(struct task_struct *t, struct list_head *hop);
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typedef void (*postscan_func_t)(struct list_head *hop);
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typedef void (*holdouts_func_t)(struct list_head *hop, bool ndrpt, bool *frptp);
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typedef void (*postgp_func_t)(struct rcu_tasks *rtp);
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/**
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* Definition for a Tasks-RCU-like mechanism.
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* @cbs_head: Head of callback list.
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* @cbs_tail: Tail pointer for callback list.
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* @cbs_wq: Wait queue allowning new callback to get kthread's attention.
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* @cbs_lock: Lock protecting callback list.
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* @kthread_ptr: This flavor's grace-period/callback-invocation kthread.
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* @gp_func: This flavor's grace-period-wait function.
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* @gp_state: Grace period's most recent state transition (debugging).
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* @gp_sleep: Per-grace-period sleep to prevent CPU-bound looping.
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* @init_fract: Initial backoff sleep interval.
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* @gp_jiffies: Time of last @gp_state transition.
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* @gp_start: Most recent grace-period start in jiffies.
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* @n_gps: Number of grace periods completed since boot.
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* @n_ipis: Number of IPIs sent to encourage grace periods to end.
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* @n_ipis_fails: Number of IPI-send failures.
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* @pregp_func: This flavor's pre-grace-period function (optional).
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* @pertask_func: This flavor's per-task scan function (optional).
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* @postscan_func: This flavor's post-task scan function (optional).
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* @holdout_func: This flavor's holdout-list scan function (optional).
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* @postgp_func: This flavor's post-grace-period function (optional).
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* @call_func: This flavor's call_rcu()-equivalent function.
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* @name: This flavor's textual name.
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* @kname: This flavor's kthread name.
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*/
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struct rcu_tasks {
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struct rcu_head *cbs_head;
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struct rcu_head **cbs_tail;
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struct wait_queue_head cbs_wq;
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raw_spinlock_t cbs_lock;
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int gp_state;
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int gp_sleep;
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int init_fract;
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unsigned long gp_jiffies;
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unsigned long gp_start;
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unsigned long n_gps;
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unsigned long n_ipis;
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unsigned long n_ipis_fails;
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struct task_struct *kthread_ptr;
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rcu_tasks_gp_func_t gp_func;
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pregp_func_t pregp_func;
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pertask_func_t pertask_func;
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postscan_func_t postscan_func;
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holdouts_func_t holdouts_func;
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postgp_func_t postgp_func;
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call_rcu_func_t call_func;
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char *name;
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char *kname;
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};
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#define DEFINE_RCU_TASKS(rt_name, gp, call, n) \
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static struct rcu_tasks rt_name = \
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{ \
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.cbs_tail = &rt_name.cbs_head, \
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.cbs_wq = __WAIT_QUEUE_HEAD_INITIALIZER(rt_name.cbs_wq), \
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.cbs_lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name.cbs_lock), \
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.gp_func = gp, \
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.call_func = call, \
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.name = n, \
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.kname = #rt_name, \
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}
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/* Track exiting tasks in order to allow them to be waited for. */
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DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
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/* Avoid IPIing CPUs early in the grace period. */
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#define RCU_TASK_IPI_DELAY (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) ? HZ / 2 : 0)
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static int rcu_task_ipi_delay __read_mostly = RCU_TASK_IPI_DELAY;
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module_param(rcu_task_ipi_delay, int, 0644);
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/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */
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#define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10)
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static int rcu_task_stall_timeout __read_mostly = RCU_TASK_STALL_TIMEOUT;
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module_param(rcu_task_stall_timeout, int, 0644);
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/* RCU tasks grace-period state for debugging. */
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#define RTGS_INIT 0
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#define RTGS_WAIT_WAIT_CBS 1
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#define RTGS_WAIT_GP 2
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#define RTGS_PRE_WAIT_GP 3
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#define RTGS_SCAN_TASKLIST 4
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#define RTGS_POST_SCAN_TASKLIST 5
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#define RTGS_WAIT_SCAN_HOLDOUTS 6
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#define RTGS_SCAN_HOLDOUTS 7
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#define RTGS_POST_GP 8
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#define RTGS_WAIT_READERS 9
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#define RTGS_INVOKE_CBS 10
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#define RTGS_WAIT_CBS 11
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#ifndef CONFIG_TINY_RCU
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static const char * const rcu_tasks_gp_state_names[] = {
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"RTGS_INIT",
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"RTGS_WAIT_WAIT_CBS",
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"RTGS_WAIT_GP",
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"RTGS_PRE_WAIT_GP",
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"RTGS_SCAN_TASKLIST",
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"RTGS_POST_SCAN_TASKLIST",
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"RTGS_WAIT_SCAN_HOLDOUTS",
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"RTGS_SCAN_HOLDOUTS",
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"RTGS_POST_GP",
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"RTGS_WAIT_READERS",
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"RTGS_INVOKE_CBS",
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"RTGS_WAIT_CBS",
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};
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#endif /* #ifndef CONFIG_TINY_RCU */
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////////////////////////////////////////////////////////////////////////
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//
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// Generic code.
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/* Record grace-period phase and time. */
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static void set_tasks_gp_state(struct rcu_tasks *rtp, int newstate)
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{
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rtp->gp_state = newstate;
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rtp->gp_jiffies = jiffies;
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}
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#ifndef CONFIG_TINY_RCU
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/* Return state name. */
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static const char *tasks_gp_state_getname(struct rcu_tasks *rtp)
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{
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int i = data_race(rtp->gp_state); // Let KCSAN detect update races
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int j = READ_ONCE(i); // Prevent the compiler from reading twice
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if (j >= ARRAY_SIZE(rcu_tasks_gp_state_names))
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return "???";
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return rcu_tasks_gp_state_names[j];
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}
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#endif /* #ifndef CONFIG_TINY_RCU */
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// Enqueue a callback for the specified flavor of Tasks RCU.
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static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func,
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struct rcu_tasks *rtp)
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{
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unsigned long flags;
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bool needwake;
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rhp->next = NULL;
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rhp->func = func;
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raw_spin_lock_irqsave(&rtp->cbs_lock, flags);
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needwake = !rtp->cbs_head;
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WRITE_ONCE(*rtp->cbs_tail, rhp);
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rtp->cbs_tail = &rhp->next;
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raw_spin_unlock_irqrestore(&rtp->cbs_lock, flags);
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/* We can't create the thread unless interrupts are enabled. */
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if (needwake && READ_ONCE(rtp->kthread_ptr))
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wake_up(&rtp->cbs_wq);
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}
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// Wait for a grace period for the specified flavor of Tasks RCU.
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static void synchronize_rcu_tasks_generic(struct rcu_tasks *rtp)
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{
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/* Complain if the scheduler has not started. */
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WARN_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE,
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"synchronize_rcu_tasks called too soon");
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/* Wait for the grace period. */
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wait_rcu_gp(rtp->call_func);
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}
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/* RCU-tasks kthread that detects grace periods and invokes callbacks. */
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static int __noreturn rcu_tasks_kthread(void *arg)
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{
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unsigned long flags;
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struct rcu_head *list;
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struct rcu_head *next;
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struct rcu_tasks *rtp = arg;
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/* Run on housekeeping CPUs by default. Sysadm can move if desired. */
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housekeeping_affine(current, HK_FLAG_RCU);
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WRITE_ONCE(rtp->kthread_ptr, current); // Let GPs start!
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/*
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* Each pass through the following loop makes one check for
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* newly arrived callbacks, and, if there are some, waits for
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* one RCU-tasks grace period and then invokes the callbacks.
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* This loop is terminated by the system going down. ;-)
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*/
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for (;;) {
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set_tasks_gp_state(rtp, RTGS_WAIT_CBS);
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/* Pick up any new callbacks. */
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raw_spin_lock_irqsave(&rtp->cbs_lock, flags);
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smp_mb__after_spinlock(); // Order updates vs. GP.
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list = rtp->cbs_head;
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rtp->cbs_head = NULL;
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rtp->cbs_tail = &rtp->cbs_head;
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raw_spin_unlock_irqrestore(&rtp->cbs_lock, flags);
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/* If there were none, wait a bit and start over. */
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if (!list) {
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wait_event_interruptible(rtp->cbs_wq,
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READ_ONCE(rtp->cbs_head));
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if (!rtp->cbs_head) {
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WARN_ON(signal_pending(current));
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set_tasks_gp_state(rtp, RTGS_WAIT_WAIT_CBS);
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schedule_timeout_idle(HZ/10);
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}
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continue;
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}
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// Wait for one grace period.
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set_tasks_gp_state(rtp, RTGS_WAIT_GP);
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rtp->gp_start = jiffies;
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rtp->gp_func(rtp);
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rtp->n_gps++;
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/* Invoke the callbacks. */
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set_tasks_gp_state(rtp, RTGS_INVOKE_CBS);
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while (list) {
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next = list->next;
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local_bh_disable();
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list->func(list);
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local_bh_enable();
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list = next;
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cond_resched();
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}
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/* Paranoid sleep to keep this from entering a tight loop */
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schedule_timeout_idle(rtp->gp_sleep);
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}
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}
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/* Spawn RCU-tasks grace-period kthread. */
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static void __init rcu_spawn_tasks_kthread_generic(struct rcu_tasks *rtp)
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{
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struct task_struct *t;
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t = kthread_run(rcu_tasks_kthread, rtp, "%s_kthread", rtp->kname);
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if (WARN_ONCE(IS_ERR(t), "%s: Could not start %s grace-period kthread, OOM is now expected behavior\n", __func__, rtp->name))
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return;
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smp_mb(); /* Ensure others see full kthread. */
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}
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#ifndef CONFIG_TINY_RCU
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/*
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* Print any non-default Tasks RCU settings.
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*/
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static void __init rcu_tasks_bootup_oddness(void)
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{
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#if defined(CONFIG_TASKS_RCU) || defined(CONFIG_TASKS_TRACE_RCU)
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if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT)
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pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout);
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#endif /* #ifdef CONFIG_TASKS_RCU */
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#ifdef CONFIG_TASKS_RCU
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pr_info("\tTrampoline variant of Tasks RCU enabled.\n");
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#endif /* #ifdef CONFIG_TASKS_RCU */
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#ifdef CONFIG_TASKS_RUDE_RCU
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pr_info("\tRude variant of Tasks RCU enabled.\n");
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#endif /* #ifdef CONFIG_TASKS_RUDE_RCU */
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#ifdef CONFIG_TASKS_TRACE_RCU
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pr_info("\tTracing variant of Tasks RCU enabled.\n");
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#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
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}
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#endif /* #ifndef CONFIG_TINY_RCU */
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#ifndef CONFIG_TINY_RCU
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/* Dump out rcutorture-relevant state common to all RCU-tasks flavors. */
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static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
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{
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pr_info("%s: %s(%d) since %lu g:%lu i:%lu/%lu %c%c %s\n",
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rtp->kname,
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tasks_gp_state_getname(rtp), data_race(rtp->gp_state),
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jiffies - data_race(rtp->gp_jiffies),
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data_race(rtp->n_gps),
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data_race(rtp->n_ipis_fails), data_race(rtp->n_ipis),
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".k"[!!data_race(rtp->kthread_ptr)],
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".C"[!!data_race(rtp->cbs_head)],
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s);
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}
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#endif /* #ifndef CONFIG_TINY_RCU */
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static void exit_tasks_rcu_finish_trace(struct task_struct *t);
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#if defined(CONFIG_TASKS_RCU) || defined(CONFIG_TASKS_TRACE_RCU)
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////////////////////////////////////////////////////////////////////////
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//
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// Shared code between task-list-scanning variants of Tasks RCU.
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/* Wait for one RCU-tasks grace period. */
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static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
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{
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struct task_struct *g, *t;
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unsigned long lastreport;
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LIST_HEAD(holdouts);
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int fract;
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set_tasks_gp_state(rtp, RTGS_PRE_WAIT_GP);
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rtp->pregp_func();
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/*
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* There were callbacks, so we need to wait for an RCU-tasks
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* grace period. Start off by scanning the task list for tasks
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* that are not already voluntarily blocked. Mark these tasks
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* and make a list of them in holdouts.
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*/
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set_tasks_gp_state(rtp, RTGS_SCAN_TASKLIST);
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rcu_read_lock();
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for_each_process_thread(g, t)
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rtp->pertask_func(t, &holdouts);
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rcu_read_unlock();
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set_tasks_gp_state(rtp, RTGS_POST_SCAN_TASKLIST);
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rtp->postscan_func(&holdouts);
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/*
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* Each pass through the following loop scans the list of holdout
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* tasks, removing any that are no longer holdouts. When the list
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* is empty, we are done.
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*/
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lastreport = jiffies;
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// Start off with initial wait and slowly back off to 1 HZ wait.
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fract = rtp->init_fract;
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if (fract > HZ)
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fract = HZ;
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for (;;) {
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bool firstreport;
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bool needreport;
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int rtst;
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if (list_empty(&holdouts))
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break;
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/* Slowly back off waiting for holdouts */
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set_tasks_gp_state(rtp, RTGS_WAIT_SCAN_HOLDOUTS);
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schedule_timeout_idle(HZ/fract);
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if (fract > 1)
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fract--;
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rtst = READ_ONCE(rcu_task_stall_timeout);
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needreport = rtst > 0 && time_after(jiffies, lastreport + rtst);
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if (needreport)
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lastreport = jiffies;
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firstreport = true;
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WARN_ON(signal_pending(current));
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set_tasks_gp_state(rtp, RTGS_SCAN_HOLDOUTS);
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rtp->holdouts_func(&holdouts, needreport, &firstreport);
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}
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set_tasks_gp_state(rtp, RTGS_POST_GP);
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rtp->postgp_func(rtp);
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}
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#endif /* #if defined(CONFIG_TASKS_RCU) || defined(CONFIG_TASKS_TRACE_RCU) */
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#ifdef CONFIG_TASKS_RCU
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////////////////////////////////////////////////////////////////////////
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//
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// Simple variant of RCU whose quiescent states are voluntary context
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// switch, cond_resched_rcu_qs(), user-space execution, and idle.
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// As such, grace periods can take one good long time. There are no
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// read-side primitives similar to rcu_read_lock() and rcu_read_unlock()
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// because this implementation is intended to get the system into a safe
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// state for some of the manipulations involved in tracing and the like.
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// Finally, this implementation does not support high call_rcu_tasks()
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// rates from multiple CPUs. If this is required, per-CPU callback lists
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// will be needed.
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/* Pre-grace-period preparation. */
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static void rcu_tasks_pregp_step(void)
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{
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/*
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* Wait for all pre-existing t->on_rq and t->nvcsw transitions
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* to complete. Invoking synchronize_rcu() suffices because all
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* these transitions occur with interrupts disabled. Without this
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* synchronize_rcu(), a read-side critical section that started
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* before the grace period might be incorrectly seen as having
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* started after the grace period.
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*
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* This synchronize_rcu() also dispenses with the need for a
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* memory barrier on the first store to t->rcu_tasks_holdout,
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* as it forces the store to happen after the beginning of the
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* grace period.
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*/
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synchronize_rcu();
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}
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/* Per-task initial processing. */
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static void rcu_tasks_pertask(struct task_struct *t, struct list_head *hop)
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{
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if (t != current && READ_ONCE(t->on_rq) && !is_idle_task(t)) {
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get_task_struct(t);
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t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
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WRITE_ONCE(t->rcu_tasks_holdout, true);
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list_add(&t->rcu_tasks_holdout_list, hop);
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}
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}
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/* Processing between scanning taskslist and draining the holdout list. */
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static void rcu_tasks_postscan(struct list_head *hop)
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{
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/*
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* Wait for tasks that are in the process of exiting. This
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* does only part of the job, ensuring that all tasks that were
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* previously exiting reach the point where they have disabled
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* preemption, allowing the later synchronize_rcu() to finish
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* the job.
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*/
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synchronize_srcu(&tasks_rcu_exit_srcu);
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}
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/* See if tasks are still holding out, complain if so. */
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static void check_holdout_task(struct task_struct *t,
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bool needreport, bool *firstreport)
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{
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int cpu;
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if (!READ_ONCE(t->rcu_tasks_holdout) ||
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t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
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!READ_ONCE(t->on_rq) ||
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(IS_ENABLED(CONFIG_NO_HZ_FULL) &&
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!is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
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WRITE_ONCE(t->rcu_tasks_holdout, false);
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list_del_init(&t->rcu_tasks_holdout_list);
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put_task_struct(t);
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return;
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}
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rcu_request_urgent_qs_task(t);
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if (!needreport)
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return;
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if (*firstreport) {
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pr_err("INFO: rcu_tasks detected stalls on tasks:\n");
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*firstreport = false;
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}
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cpu = task_cpu(t);
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pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n",
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t, ".I"[is_idle_task(t)],
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"N."[cpu < 0 || !tick_nohz_full_cpu(cpu)],
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t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
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t->rcu_tasks_idle_cpu, cpu);
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sched_show_task(t);
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}
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/* Scan the holdout lists for tasks no longer holding out. */
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static void check_all_holdout_tasks(struct list_head *hop,
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bool needreport, bool *firstreport)
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{
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struct task_struct *t, *t1;
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list_for_each_entry_safe(t, t1, hop, rcu_tasks_holdout_list) {
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check_holdout_task(t, needreport, firstreport);
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cond_resched();
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}
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}
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/* Finish off the Tasks-RCU grace period. */
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static void rcu_tasks_postgp(struct rcu_tasks *rtp)
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{
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/*
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* Because ->on_rq and ->nvcsw are not guaranteed to have a full
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* memory barriers prior to them in the schedule() path, memory
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* reordering on other CPUs could cause their RCU-tasks read-side
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* critical sections to extend past the end of the grace period.
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* However, because these ->nvcsw updates are carried out with
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* interrupts disabled, we can use synchronize_rcu() to force the
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* needed ordering on all such CPUs.
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*
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* This synchronize_rcu() also confines all ->rcu_tasks_holdout
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* accesses to be within the grace period, avoiding the need for
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* memory barriers for ->rcu_tasks_holdout accesses.
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*
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* In addition, this synchronize_rcu() waits for exiting tasks
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* to complete their final preempt_disable() region of execution,
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* cleaning up after the synchronize_srcu() above.
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*/
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synchronize_rcu();
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}
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void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func);
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DEFINE_RCU_TASKS(rcu_tasks, rcu_tasks_wait_gp, call_rcu_tasks, "RCU Tasks");
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/**
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* call_rcu_tasks() - Queue an RCU for invocation task-based grace period
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* @rhp: structure to be used for queueing the RCU updates.
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* @func: actual callback function to be invoked after the grace period
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*
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* The callback function will be invoked some time after a full grace
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* period elapses, in other words after all currently executing RCU
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* read-side critical sections have completed. call_rcu_tasks() assumes
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* that the read-side critical sections end at a voluntary context
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* switch (not a preemption!), cond_resched_rcu_qs(), entry into idle,
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* or transition to usermode execution. As such, there are no read-side
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* primitives analogous to rcu_read_lock() and rcu_read_unlock() because
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* this primitive is intended to determine that all tasks have passed
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* through a safe state, not so much for data-strcuture synchronization.
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*
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* See the description of call_rcu() for more detailed information on
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* memory ordering guarantees.
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*/
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void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func)
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{
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call_rcu_tasks_generic(rhp, func, &rcu_tasks);
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}
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EXPORT_SYMBOL_GPL(call_rcu_tasks);
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/**
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* synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed.
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*
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* Control will return to the caller some time after a full rcu-tasks
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* grace period has elapsed, in other words after all currently
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* executing rcu-tasks read-side critical sections have elapsed. These
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* read-side critical sections are delimited by calls to schedule(),
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* cond_resched_tasks_rcu_qs(), idle execution, userspace execution, calls
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* to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
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*
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* This is a very specialized primitive, intended only for a few uses in
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* tracing and other situations requiring manipulation of function
|
* preambles and profiling hooks. The synchronize_rcu_tasks() function
|
* is not (yet) intended for heavy use from multiple CPUs.
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*
|
* See the description of synchronize_rcu() for more detailed information
|
* on memory ordering guarantees.
|
*/
|
void synchronize_rcu_tasks(void)
|
{
|
synchronize_rcu_tasks_generic(&rcu_tasks);
|
}
|
EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
|
|
/**
|
* rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
|
*
|
* Although the current implementation is guaranteed to wait, it is not
|
* obligated to, for example, if there are no pending callbacks.
|
*/
|
void rcu_barrier_tasks(void)
|
{
|
/* There is only one callback queue, so this is easy. ;-) */
|
synchronize_rcu_tasks();
|
}
|
EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
|
|
static int __init rcu_spawn_tasks_kthread(void)
|
{
|
rcu_tasks.gp_sleep = HZ / 10;
|
rcu_tasks.init_fract = 10;
|
rcu_tasks.pregp_func = rcu_tasks_pregp_step;
|
rcu_tasks.pertask_func = rcu_tasks_pertask;
|
rcu_tasks.postscan_func = rcu_tasks_postscan;
|
rcu_tasks.holdouts_func = check_all_holdout_tasks;
|
rcu_tasks.postgp_func = rcu_tasks_postgp;
|
rcu_spawn_tasks_kthread_generic(&rcu_tasks);
|
return 0;
|
}
|
|
#ifndef CONFIG_TINY_RCU
|
static void show_rcu_tasks_classic_gp_kthread(void)
|
{
|
show_rcu_tasks_generic_gp_kthread(&rcu_tasks, "");
|
}
|
#endif /* #ifndef CONFIG_TINY_RCU */
|
|
/* Do the srcu_read_lock() for the above synchronize_srcu(). */
|
void exit_tasks_rcu_start(void) __acquires(&tasks_rcu_exit_srcu)
|
{
|
preempt_disable();
|
current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu);
|
preempt_enable();
|
}
|
|
/* Do the srcu_read_unlock() for the above synchronize_srcu(). */
|
void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
|
{
|
struct task_struct *t = current;
|
|
preempt_disable();
|
__srcu_read_unlock(&tasks_rcu_exit_srcu, t->rcu_tasks_idx);
|
preempt_enable();
|
exit_tasks_rcu_finish_trace(t);
|
}
|
|
#else /* #ifdef CONFIG_TASKS_RCU */
|
static inline void show_rcu_tasks_classic_gp_kthread(void) { }
|
void exit_tasks_rcu_start(void) { }
|
void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
|
#endif /* #else #ifdef CONFIG_TASKS_RCU */
|
|
#ifdef CONFIG_TASKS_RUDE_RCU
|
|
////////////////////////////////////////////////////////////////////////
|
//
|
// "Rude" variant of Tasks RCU, inspired by Steve Rostedt's trick of
|
// passing an empty function to schedule_on_each_cpu(). This approach
|
// provides an asynchronous call_rcu_tasks_rude() API and batching
|
// of concurrent calls to the synchronous synchronize_rcu_rude() API.
|
// This sends IPIs far and wide and induces otherwise unnecessary context
|
// switches on all online CPUs, whether idle or not.
|
|
// Empty function to allow workqueues to force a context switch.
|
static void rcu_tasks_be_rude(struct work_struct *work)
|
{
|
}
|
|
// Wait for one rude RCU-tasks grace period.
|
static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp)
|
{
|
if (num_online_cpus() <= 1)
|
return; // Fastpath for only one CPU.
|
|
rtp->n_ipis += cpumask_weight(cpu_online_mask);
|
schedule_on_each_cpu(rcu_tasks_be_rude);
|
}
|
|
void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback_t func);
|
DEFINE_RCU_TASKS(rcu_tasks_rude, rcu_tasks_rude_wait_gp, call_rcu_tasks_rude,
|
"RCU Tasks Rude");
|
|
/**
|
* call_rcu_tasks_rude() - Queue a callback rude task-based grace period
|
* @rhp: structure to be used for queueing the RCU updates.
|
* @func: actual callback function to be invoked after the grace period
|
*
|
* The callback function will be invoked some time after a full grace
|
* period elapses, in other words after all currently executing RCU
|
* read-side critical sections have completed. call_rcu_tasks_rude()
|
* assumes that the read-side critical sections end at context switch,
|
* cond_resched_rcu_qs(), or transition to usermode execution. As such,
|
* there are no read-side primitives analogous to rcu_read_lock() and
|
* rcu_read_unlock() because this primitive is intended to determine
|
* that all tasks have passed through a safe state, not so much for
|
* data-strcuture synchronization.
|
*
|
* See the description of call_rcu() for more detailed information on
|
* memory ordering guarantees.
|
*/
|
void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback_t func)
|
{
|
call_rcu_tasks_generic(rhp, func, &rcu_tasks_rude);
|
}
|
EXPORT_SYMBOL_GPL(call_rcu_tasks_rude);
|
|
/**
|
* synchronize_rcu_tasks_rude - wait for a rude rcu-tasks grace period
|
*
|
* Control will return to the caller some time after a rude rcu-tasks
|
* grace period has elapsed, in other words after all currently
|
* executing rcu-tasks read-side critical sections have elapsed. These
|
* read-side critical sections are delimited by calls to schedule(),
|
* cond_resched_tasks_rcu_qs(), userspace execution, and (in theory,
|
* anyway) cond_resched().
|
*
|
* This is a very specialized primitive, intended only for a few uses in
|
* tracing and other situations requiring manipulation of function preambles
|
* and profiling hooks. The synchronize_rcu_tasks_rude() function is not
|
* (yet) intended for heavy use from multiple CPUs.
|
*
|
* See the description of synchronize_rcu() for more detailed information
|
* on memory ordering guarantees.
|
*/
|
void synchronize_rcu_tasks_rude(void)
|
{
|
synchronize_rcu_tasks_generic(&rcu_tasks_rude);
|
}
|
EXPORT_SYMBOL_GPL(synchronize_rcu_tasks_rude);
|
|
/**
|
* rcu_barrier_tasks_rude - Wait for in-flight call_rcu_tasks_rude() callbacks.
|
*
|
* Although the current implementation is guaranteed to wait, it is not
|
* obligated to, for example, if there are no pending callbacks.
|
*/
|
void rcu_barrier_tasks_rude(void)
|
{
|
/* There is only one callback queue, so this is easy. ;-) */
|
synchronize_rcu_tasks_rude();
|
}
|
EXPORT_SYMBOL_GPL(rcu_barrier_tasks_rude);
|
|
static int __init rcu_spawn_tasks_rude_kthread(void)
|
{
|
rcu_tasks_rude.gp_sleep = HZ / 10;
|
rcu_spawn_tasks_kthread_generic(&rcu_tasks_rude);
|
return 0;
|
}
|
|
#ifndef CONFIG_TINY_RCU
|
static void show_rcu_tasks_rude_gp_kthread(void)
|
{
|
show_rcu_tasks_generic_gp_kthread(&rcu_tasks_rude, "");
|
}
|
#endif /* #ifndef CONFIG_TINY_RCU */
|
|
#else /* #ifdef CONFIG_TASKS_RUDE_RCU */
|
static void show_rcu_tasks_rude_gp_kthread(void) {}
|
#endif /* #else #ifdef CONFIG_TASKS_RUDE_RCU */
|
|
////////////////////////////////////////////////////////////////////////
|
//
|
// Tracing variant of Tasks RCU. This variant is designed to be used
|
// to protect tracing hooks, including those of BPF. This variant
|
// therefore:
|
//
|
// 1. Has explicit read-side markers to allow finite grace periods
|
// in the face of in-kernel loops for PREEMPT=n builds.
|
//
|
// 2. Protects code in the idle loop, exception entry/exit, and
|
// CPU-hotplug code paths, similar to the capabilities of SRCU.
|
//
|
// 3. Avoids expensive read-side instruction, having overhead similar
|
// to that of Preemptible RCU.
|
//
|
// There are of course downsides. The grace-period code can send IPIs to
|
// CPUs, even when those CPUs are in the idle loop or in nohz_full userspace.
|
// It is necessary to scan the full tasklist, much as for Tasks RCU. There
|
// is a single callback queue guarded by a single lock, again, much as for
|
// Tasks RCU. If needed, these downsides can be at least partially remedied.
|
//
|
// Perhaps most important, this variant of RCU does not affect the vanilla
|
// flavors, rcu_preempt and rcu_sched. The fact that RCU Tasks Trace
|
// readers can operate from idle, offline, and exception entry/exit in no
|
// way allows rcu_preempt and rcu_sched readers to also do so.
|
|
// The lockdep state must be outside of #ifdef to be useful.
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
static struct lock_class_key rcu_lock_trace_key;
|
struct lockdep_map rcu_trace_lock_map =
|
STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_trace", &rcu_lock_trace_key);
|
EXPORT_SYMBOL_GPL(rcu_trace_lock_map);
|
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
|
|
#ifdef CONFIG_TASKS_TRACE_RCU
|
|
static atomic_t trc_n_readers_need_end; // Number of waited-for readers.
|
static DECLARE_WAIT_QUEUE_HEAD(trc_wait); // List of holdout tasks.
|
|
// Record outstanding IPIs to each CPU. No point in sending two...
|
static DEFINE_PER_CPU(bool, trc_ipi_to_cpu);
|
|
// The number of detections of task quiescent state relying on
|
// heavyweight readers executing explicit memory barriers.
|
static unsigned long n_heavy_reader_attempts;
|
static unsigned long n_heavy_reader_updates;
|
static unsigned long n_heavy_reader_ofl_updates;
|
|
void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);
|
DEFINE_RCU_TASKS(rcu_tasks_trace, rcu_tasks_wait_gp, call_rcu_tasks_trace,
|
"RCU Tasks Trace");
|
|
/*
|
* This irq_work handler allows rcu_read_unlock_trace() to be invoked
|
* while the scheduler locks are held.
|
*/
|
static void rcu_read_unlock_iw(struct irq_work *iwp)
|
{
|
wake_up(&trc_wait);
|
}
|
static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw);
|
|
/* If we are the last reader, wake up the grace-period kthread. */
|
void rcu_read_unlock_trace_special(struct task_struct *t, int nesting)
|
{
|
int nq = t->trc_reader_special.b.need_qs;
|
|
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) &&
|
t->trc_reader_special.b.need_mb)
|
smp_mb(); // Pairs with update-side barriers.
|
// Update .need_qs before ->trc_reader_nesting for irq/NMI handlers.
|
if (nq)
|
WRITE_ONCE(t->trc_reader_special.b.need_qs, false);
|
WRITE_ONCE(t->trc_reader_nesting, nesting);
|
if (nq && atomic_dec_and_test(&trc_n_readers_need_end))
|
irq_work_queue(&rcu_tasks_trace_iw);
|
}
|
EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
|
|
/* Add a task to the holdout list, if it is not already on the list. */
|
static void trc_add_holdout(struct task_struct *t, struct list_head *bhp)
|
{
|
if (list_empty(&t->trc_holdout_list)) {
|
get_task_struct(t);
|
list_add(&t->trc_holdout_list, bhp);
|
}
|
}
|
|
/* Remove a task from the holdout list, if it is in fact present. */
|
static void trc_del_holdout(struct task_struct *t)
|
{
|
if (!list_empty(&t->trc_holdout_list)) {
|
list_del_init(&t->trc_holdout_list);
|
put_task_struct(t);
|
}
|
}
|
|
/* IPI handler to check task state. */
|
static void trc_read_check_handler(void *t_in)
|
{
|
struct task_struct *t = current;
|
struct task_struct *texp = t_in;
|
|
// If the task is no longer running on this CPU, leave.
|
if (unlikely(texp != t)) {
|
if (WARN_ON_ONCE(atomic_dec_and_test(&trc_n_readers_need_end)))
|
wake_up(&trc_wait);
|
goto reset_ipi; // Already on holdout list, so will check later.
|
}
|
|
// If the task is not in a read-side critical section, and
|
// if this is the last reader, awaken the grace-period kthread.
|
if (likely(!t->trc_reader_nesting)) {
|
if (WARN_ON_ONCE(atomic_dec_and_test(&trc_n_readers_need_end)))
|
wake_up(&trc_wait);
|
// Mark as checked after decrement to avoid false
|
// positives on the above WARN_ON_ONCE().
|
WRITE_ONCE(t->trc_reader_checked, true);
|
goto reset_ipi;
|
}
|
// If we are racing with an rcu_read_unlock_trace(), try again later.
|
if (unlikely(t->trc_reader_nesting < 0)) {
|
if (WARN_ON_ONCE(atomic_dec_and_test(&trc_n_readers_need_end)))
|
wake_up(&trc_wait);
|
goto reset_ipi;
|
}
|
WRITE_ONCE(t->trc_reader_checked, true);
|
|
// Get here if the task is in a read-side critical section. Set
|
// its state so that it will awaken the grace-period kthread upon
|
// exit from that critical section.
|
WARN_ON_ONCE(t->trc_reader_special.b.need_qs);
|
WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
|
|
reset_ipi:
|
// Allow future IPIs to be sent on CPU and for task.
|
// Also order this IPI handler against any later manipulations of
|
// the intended task.
|
smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
|
smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
|
}
|
|
/* Callback function for scheduler to check locked-down task. */
|
static bool trc_inspect_reader(struct task_struct *t, void *arg)
|
{
|
int cpu = task_cpu(t);
|
bool in_qs = false;
|
bool ofl = cpu_is_offline(cpu);
|
|
if (task_curr(t)) {
|
WARN_ON_ONCE(ofl && !is_idle_task(t));
|
|
// If no chance of heavyweight readers, do it the hard way.
|
if (!ofl && !IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
|
return false;
|
|
// If heavyweight readers are enabled on the remote task,
|
// we can inspect its state despite its currently running.
|
// However, we cannot safely change its state.
|
n_heavy_reader_attempts++;
|
if (!ofl && // Check for "running" idle tasks on offline CPUs.
|
!rcu_dynticks_zero_in_eqs(cpu, &t->trc_reader_nesting))
|
return false; // No quiescent state, do it the hard way.
|
n_heavy_reader_updates++;
|
if (ofl)
|
n_heavy_reader_ofl_updates++;
|
in_qs = true;
|
} else {
|
in_qs = likely(!t->trc_reader_nesting);
|
}
|
|
// Mark as checked so that the grace-period kthread will
|
// remove it from the holdout list.
|
t->trc_reader_checked = true;
|
|
if (in_qs)
|
return true; // Already in quiescent state, done!!!
|
|
// The task is in a read-side critical section, so set up its
|
// state so that it will awaken the grace-period kthread upon exit
|
// from that critical section.
|
atomic_inc(&trc_n_readers_need_end); // One more to wait on.
|
WARN_ON_ONCE(t->trc_reader_special.b.need_qs);
|
WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
|
return true;
|
}
|
|
/* Attempt to extract the state for the specified task. */
|
static void trc_wait_for_one_reader(struct task_struct *t,
|
struct list_head *bhp)
|
{
|
int cpu;
|
|
// If a previous IPI is still in flight, let it complete.
|
if (smp_load_acquire(&t->trc_ipi_to_cpu) != -1) // Order IPI
|
return;
|
|
// The current task had better be in a quiescent state.
|
if (t == current) {
|
t->trc_reader_checked = true;
|
WARN_ON_ONCE(t->trc_reader_nesting);
|
return;
|
}
|
|
// Attempt to nail down the task for inspection.
|
get_task_struct(t);
|
if (try_invoke_on_locked_down_task(t, trc_inspect_reader, NULL)) {
|
put_task_struct(t);
|
return;
|
}
|
put_task_struct(t);
|
|
// If currently running, send an IPI, either way, add to list.
|
trc_add_holdout(t, bhp);
|
if (task_curr(t) &&
|
time_after(jiffies + 1, rcu_tasks_trace.gp_start + rcu_task_ipi_delay)) {
|
// The task is currently running, so try IPIing it.
|
cpu = task_cpu(t);
|
|
// If there is already an IPI outstanding, let it happen.
|
if (per_cpu(trc_ipi_to_cpu, cpu) || t->trc_ipi_to_cpu >= 0)
|
return;
|
|
atomic_inc(&trc_n_readers_need_end);
|
per_cpu(trc_ipi_to_cpu, cpu) = true;
|
t->trc_ipi_to_cpu = cpu;
|
rcu_tasks_trace.n_ipis++;
|
if (smp_call_function_single(cpu,
|
trc_read_check_handler, t, 0)) {
|
// Just in case there is some other reason for
|
// failure than the target CPU being offline.
|
rcu_tasks_trace.n_ipis_fails++;
|
per_cpu(trc_ipi_to_cpu, cpu) = false;
|
t->trc_ipi_to_cpu = cpu;
|
if (atomic_dec_and_test(&trc_n_readers_need_end)) {
|
WARN_ON_ONCE(1);
|
wake_up(&trc_wait);
|
}
|
}
|
}
|
}
|
|
/* Initialize for a new RCU-tasks-trace grace period. */
|
static void rcu_tasks_trace_pregp_step(void)
|
{
|
int cpu;
|
|
// Allow for fast-acting IPIs.
|
atomic_set(&trc_n_readers_need_end, 1);
|
|
// There shouldn't be any old IPIs, but...
|
for_each_possible_cpu(cpu)
|
WARN_ON_ONCE(per_cpu(trc_ipi_to_cpu, cpu));
|
|
// Disable CPU hotplug across the tasklist scan.
|
// This also waits for all readers in CPU-hotplug code paths.
|
cpus_read_lock();
|
}
|
|
/* Do first-round processing for the specified task. */
|
static void rcu_tasks_trace_pertask(struct task_struct *t,
|
struct list_head *hop)
|
{
|
// During early boot when there is only the one boot CPU, there
|
// is no idle task for the other CPUs. Just return.
|
if (unlikely(t == NULL))
|
return;
|
|
WRITE_ONCE(t->trc_reader_special.b.need_qs, false);
|
WRITE_ONCE(t->trc_reader_checked, false);
|
t->trc_ipi_to_cpu = -1;
|
trc_wait_for_one_reader(t, hop);
|
}
|
|
/*
|
* Do intermediate processing between task and holdout scans and
|
* pick up the idle tasks.
|
*/
|
static void rcu_tasks_trace_postscan(struct list_head *hop)
|
{
|
int cpu;
|
|
for_each_possible_cpu(cpu)
|
rcu_tasks_trace_pertask(idle_task(cpu), hop);
|
|
// Re-enable CPU hotplug now that the tasklist scan has completed.
|
cpus_read_unlock();
|
|
// Wait for late-stage exiting tasks to finish exiting.
|
// These might have passed the call to exit_tasks_rcu_finish().
|
synchronize_rcu();
|
// Any tasks that exit after this point will set ->trc_reader_checked.
|
}
|
|
/* Show the state of a task stalling the current RCU tasks trace GP. */
|
static void show_stalled_task_trace(struct task_struct *t, bool *firstreport)
|
{
|
int cpu;
|
|
if (*firstreport) {
|
pr_err("INFO: rcu_tasks_trace detected stalls on tasks:\n");
|
*firstreport = false;
|
}
|
// FIXME: This should attempt to use try_invoke_on_nonrunning_task().
|
cpu = task_cpu(t);
|
pr_alert("P%d: %c%c%c nesting: %d%c cpu: %d\n",
|
t->pid,
|
".I"[READ_ONCE(t->trc_ipi_to_cpu) > 0],
|
".i"[is_idle_task(t)],
|
".N"[cpu > 0 && tick_nohz_full_cpu(cpu)],
|
t->trc_reader_nesting,
|
" N"[!!t->trc_reader_special.b.need_qs],
|
cpu);
|
sched_show_task(t);
|
}
|
|
/* List stalled IPIs for RCU tasks trace. */
|
static void show_stalled_ipi_trace(void)
|
{
|
int cpu;
|
|
for_each_possible_cpu(cpu)
|
if (per_cpu(trc_ipi_to_cpu, cpu))
|
pr_alert("\tIPI outstanding to CPU %d\n", cpu);
|
}
|
|
/* Do one scan of the holdout list. */
|
static void check_all_holdout_tasks_trace(struct list_head *hop,
|
bool needreport, bool *firstreport)
|
{
|
struct task_struct *g, *t;
|
|
// Disable CPU hotplug across the holdout list scan.
|
cpus_read_lock();
|
|
list_for_each_entry_safe(t, g, hop, trc_holdout_list) {
|
// If safe and needed, try to check the current task.
|
if (READ_ONCE(t->trc_ipi_to_cpu) == -1 &&
|
!READ_ONCE(t->trc_reader_checked))
|
trc_wait_for_one_reader(t, hop);
|
|
// If check succeeded, remove this task from the list.
|
if (READ_ONCE(t->trc_reader_checked))
|
trc_del_holdout(t);
|
else if (needreport)
|
show_stalled_task_trace(t, firstreport);
|
}
|
|
// Re-enable CPU hotplug now that the holdout list scan has completed.
|
cpus_read_unlock();
|
|
if (needreport) {
|
if (firstreport)
|
pr_err("INFO: rcu_tasks_trace detected stalls? (Late IPI?)\n");
|
show_stalled_ipi_trace();
|
}
|
}
|
|
/* Wait for grace period to complete and provide ordering. */
|
static void rcu_tasks_trace_postgp(struct rcu_tasks *rtp)
|
{
|
bool firstreport;
|
struct task_struct *g, *t;
|
LIST_HEAD(holdouts);
|
long ret;
|
|
// Remove the safety count.
|
smp_mb__before_atomic(); // Order vs. earlier atomics
|
atomic_dec(&trc_n_readers_need_end);
|
smp_mb__after_atomic(); // Order vs. later atomics
|
|
// Wait for readers.
|
set_tasks_gp_state(rtp, RTGS_WAIT_READERS);
|
for (;;) {
|
ret = wait_event_idle_exclusive_timeout(
|
trc_wait,
|
atomic_read(&trc_n_readers_need_end) == 0,
|
READ_ONCE(rcu_task_stall_timeout));
|
if (ret)
|
break; // Count reached zero.
|
// Stall warning time, so make a list of the offenders.
|
rcu_read_lock();
|
for_each_process_thread(g, t)
|
if (READ_ONCE(t->trc_reader_special.b.need_qs))
|
trc_add_holdout(t, &holdouts);
|
rcu_read_unlock();
|
firstreport = true;
|
list_for_each_entry_safe(t, g, &holdouts, trc_holdout_list) {
|
if (READ_ONCE(t->trc_reader_special.b.need_qs))
|
show_stalled_task_trace(t, &firstreport);
|
trc_del_holdout(t); // Release task_struct reference.
|
}
|
if (firstreport)
|
pr_err("INFO: rcu_tasks_trace detected stalls? (Counter/taskslist mismatch?)\n");
|
show_stalled_ipi_trace();
|
pr_err("\t%d holdouts\n", atomic_read(&trc_n_readers_need_end));
|
}
|
smp_mb(); // Caller's code must be ordered after wakeup.
|
// Pairs with pretty much every ordering primitive.
|
}
|
|
/* Report any needed quiescent state for this exiting task. */
|
static void exit_tasks_rcu_finish_trace(struct task_struct *t)
|
{
|
WRITE_ONCE(t->trc_reader_checked, true);
|
WARN_ON_ONCE(t->trc_reader_nesting);
|
WRITE_ONCE(t->trc_reader_nesting, 0);
|
if (WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs)))
|
rcu_read_unlock_trace_special(t, 0);
|
}
|
|
/**
|
* call_rcu_tasks_trace() - Queue a callback trace task-based grace period
|
* @rhp: structure to be used for queueing the RCU updates.
|
* @func: actual callback function to be invoked after the grace period
|
*
|
* The callback function will be invoked some time after a full grace
|
* period elapses, in other words after all currently executing RCU
|
* read-side critical sections have completed. call_rcu_tasks_trace()
|
* assumes that the read-side critical sections end at context switch,
|
* cond_resched_rcu_qs(), or transition to usermode execution. As such,
|
* there are no read-side primitives analogous to rcu_read_lock() and
|
* rcu_read_unlock() because this primitive is intended to determine
|
* that all tasks have passed through a safe state, not so much for
|
* data-strcuture synchronization.
|
*
|
* See the description of call_rcu() for more detailed information on
|
* memory ordering guarantees.
|
*/
|
void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func)
|
{
|
call_rcu_tasks_generic(rhp, func, &rcu_tasks_trace);
|
}
|
EXPORT_SYMBOL_GPL(call_rcu_tasks_trace);
|
|
/**
|
* synchronize_rcu_tasks_trace - wait for a trace rcu-tasks grace period
|
*
|
* Control will return to the caller some time after a trace rcu-tasks
|
* grace period has elapsed, in other words after all currently executing
|
* rcu-tasks read-side critical sections have elapsed. These read-side
|
* critical sections are delimited by calls to rcu_read_lock_trace()
|
* and rcu_read_unlock_trace().
|
*
|
* This is a very specialized primitive, intended only for a few uses in
|
* tracing and other situations requiring manipulation of function preambles
|
* and profiling hooks. The synchronize_rcu_tasks_trace() function is not
|
* (yet) intended for heavy use from multiple CPUs.
|
*
|
* See the description of synchronize_rcu() for more detailed information
|
* on memory ordering guarantees.
|
*/
|
void synchronize_rcu_tasks_trace(void)
|
{
|
RCU_LOCKDEP_WARN(lock_is_held(&rcu_trace_lock_map), "Illegal synchronize_rcu_tasks_trace() in RCU Tasks Trace read-side critical section");
|
synchronize_rcu_tasks_generic(&rcu_tasks_trace);
|
}
|
EXPORT_SYMBOL_GPL(synchronize_rcu_tasks_trace);
|
|
/**
|
* rcu_barrier_tasks_trace - Wait for in-flight call_rcu_tasks_trace() callbacks.
|
*
|
* Although the current implementation is guaranteed to wait, it is not
|
* obligated to, for example, if there are no pending callbacks.
|
*/
|
void rcu_barrier_tasks_trace(void)
|
{
|
/* There is only one callback queue, so this is easy. ;-) */
|
synchronize_rcu_tasks_trace();
|
}
|
EXPORT_SYMBOL_GPL(rcu_barrier_tasks_trace);
|
|
static int __init rcu_spawn_tasks_trace_kthread(void)
|
{
|
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) {
|
rcu_tasks_trace.gp_sleep = HZ / 10;
|
rcu_tasks_trace.init_fract = 10;
|
} else {
|
rcu_tasks_trace.gp_sleep = HZ / 200;
|
if (rcu_tasks_trace.gp_sleep <= 0)
|
rcu_tasks_trace.gp_sleep = 1;
|
rcu_tasks_trace.init_fract = HZ / 5;
|
if (rcu_tasks_trace.init_fract <= 0)
|
rcu_tasks_trace.init_fract = 1;
|
}
|
rcu_tasks_trace.pregp_func = rcu_tasks_trace_pregp_step;
|
rcu_tasks_trace.pertask_func = rcu_tasks_trace_pertask;
|
rcu_tasks_trace.postscan_func = rcu_tasks_trace_postscan;
|
rcu_tasks_trace.holdouts_func = check_all_holdout_tasks_trace;
|
rcu_tasks_trace.postgp_func = rcu_tasks_trace_postgp;
|
rcu_spawn_tasks_kthread_generic(&rcu_tasks_trace);
|
return 0;
|
}
|
|
#ifndef CONFIG_TINY_RCU
|
static void show_rcu_tasks_trace_gp_kthread(void)
|
{
|
char buf[64];
|
|
sprintf(buf, "N%d h:%lu/%lu/%lu", atomic_read(&trc_n_readers_need_end),
|
data_race(n_heavy_reader_ofl_updates),
|
data_race(n_heavy_reader_updates),
|
data_race(n_heavy_reader_attempts));
|
show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf);
|
}
|
#endif /* #ifndef CONFIG_TINY_RCU */
|
|
#else /* #ifdef CONFIG_TASKS_TRACE_RCU */
|
static void exit_tasks_rcu_finish_trace(struct task_struct *t) { }
|
static inline void show_rcu_tasks_trace_gp_kthread(void) {}
|
#endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */
|
|
#ifndef CONFIG_TINY_RCU
|
void show_rcu_tasks_gp_kthreads(void)
|
{
|
show_rcu_tasks_classic_gp_kthread();
|
show_rcu_tasks_rude_gp_kthread();
|
show_rcu_tasks_trace_gp_kthread();
|
}
|
#endif /* #ifndef CONFIG_TINY_RCU */
|
|
void __init rcu_init_tasks_generic(void)
|
{
|
#ifdef CONFIG_TASKS_RCU
|
rcu_spawn_tasks_kthread();
|
#endif
|
|
#ifdef CONFIG_TASKS_RUDE_RCU
|
rcu_spawn_tasks_rude_kthread();
|
#endif
|
|
#ifdef CONFIG_TASKS_TRACE_RCU
|
rcu_spawn_tasks_trace_kthread();
|
#endif
|
}
|
|
#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
|
static inline void rcu_tasks_bootup_oddness(void) {}
|
void show_rcu_tasks_gp_kthreads(void) {}
|
#endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */
|
