/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* Read-Copy Update definitions shared among RCU implementations.
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*
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* Copyright IBM Corporation, 2011
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*
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* Author: Paul E. McKenney <paulmck@linux.ibm.com>
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*/
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#ifndef __LINUX_RCU_H
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#define __LINUX_RCU_H
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#include <trace/events/rcu.h>
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/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
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#define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
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/*
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* Grace-period counter management.
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*/
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#define RCU_SEQ_CTR_SHIFT 2
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#define RCU_SEQ_STATE_MASK ((1 << RCU_SEQ_CTR_SHIFT) - 1)
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/*
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* Return the counter portion of a sequence number previously returned
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* by rcu_seq_snap() or rcu_seq_current().
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*/
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static inline unsigned long rcu_seq_ctr(unsigned long s)
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{
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return s >> RCU_SEQ_CTR_SHIFT;
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}
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/*
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* Return the state portion of a sequence number previously returned
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* by rcu_seq_snap() or rcu_seq_current().
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*/
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static inline int rcu_seq_state(unsigned long s)
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{
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return s & RCU_SEQ_STATE_MASK;
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}
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/*
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* Set the state portion of the pointed-to sequence number.
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* The caller is responsible for preventing conflicting updates.
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*/
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static inline void rcu_seq_set_state(unsigned long *sp, int newstate)
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{
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WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK);
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WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate);
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}
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/* Adjust sequence number for start of update-side operation. */
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static inline void rcu_seq_start(unsigned long *sp)
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{
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WRITE_ONCE(*sp, *sp + 1);
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smp_mb(); /* Ensure update-side operation after counter increment. */
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WARN_ON_ONCE(rcu_seq_state(*sp) != 1);
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}
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/* Compute the end-of-grace-period value for the specified sequence number. */
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static inline unsigned long rcu_seq_endval(unsigned long *sp)
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{
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return (*sp | RCU_SEQ_STATE_MASK) + 1;
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}
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/* Adjust sequence number for end of update-side operation. */
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static inline void rcu_seq_end(unsigned long *sp)
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{
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smp_mb(); /* Ensure update-side operation before counter increment. */
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WARN_ON_ONCE(!rcu_seq_state(*sp));
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WRITE_ONCE(*sp, rcu_seq_endval(sp));
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}
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/*
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* rcu_seq_snap - Take a snapshot of the update side's sequence number.
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*
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* This function returns the earliest value of the grace-period sequence number
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* that will indicate that a full grace period has elapsed since the current
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* time. Once the grace-period sequence number has reached this value, it will
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* be safe to invoke all callbacks that have been registered prior to the
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* current time. This value is the current grace-period number plus two to the
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* power of the number of low-order bits reserved for state, then rounded up to
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* the next value in which the state bits are all zero.
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*/
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static inline unsigned long rcu_seq_snap(unsigned long *sp)
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{
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unsigned long s;
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s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK;
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smp_mb(); /* Above access must not bleed into critical section. */
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return s;
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}
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/* Return the current value the update side's sequence number, no ordering. */
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static inline unsigned long rcu_seq_current(unsigned long *sp)
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{
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return READ_ONCE(*sp);
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}
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/*
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* Given a snapshot from rcu_seq_snap(), determine whether or not the
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* corresponding update-side operation has started.
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*/
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static inline bool rcu_seq_started(unsigned long *sp, unsigned long s)
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{
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return ULONG_CMP_LT((s - 1) & ~RCU_SEQ_STATE_MASK, READ_ONCE(*sp));
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}
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/*
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* Given a snapshot from rcu_seq_snap(), determine whether or not a
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* full update-side operation has occurred.
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*/
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static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
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{
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return ULONG_CMP_GE(READ_ONCE(*sp), s);
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}
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/*
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* Has a grace period completed since the time the old gp_seq was collected?
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*/
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static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new)
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{
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return ULONG_CMP_LT(old, new & ~RCU_SEQ_STATE_MASK);
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}
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/*
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* Has a grace period started since the time the old gp_seq was collected?
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*/
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static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new)
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{
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return ULONG_CMP_LT((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK,
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new);
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}
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/*
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* Roughly how many full grace periods have elapsed between the collection
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* of the two specified grace periods?
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*/
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static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
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{
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unsigned long rnd_diff;
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if (old == new)
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return 0;
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/*
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* Compute the number of grace periods (still shifted up), plus
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* one if either of new and old is not an exact grace period.
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*/
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rnd_diff = (new & ~RCU_SEQ_STATE_MASK) -
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((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK) +
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((new & RCU_SEQ_STATE_MASK) || (old & RCU_SEQ_STATE_MASK));
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if (ULONG_CMP_GE(RCU_SEQ_STATE_MASK, rnd_diff))
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return 1; /* Definitely no grace period has elapsed. */
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return ((rnd_diff - RCU_SEQ_STATE_MASK - 1) >> RCU_SEQ_CTR_SHIFT) + 2;
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}
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/*
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* debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
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* by call_rcu() and rcu callback execution, and are therefore not part
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* of the RCU API. These are in rcupdate.h because they are used by all
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* RCU implementations.
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*/
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#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
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# define STATE_RCU_HEAD_READY 0
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# define STATE_RCU_HEAD_QUEUED 1
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extern const struct debug_obj_descr rcuhead_debug_descr;
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static inline int debug_rcu_head_queue(struct rcu_head *head)
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{
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int r1;
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r1 = debug_object_activate(head, &rcuhead_debug_descr);
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debug_object_active_state(head, &rcuhead_debug_descr,
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STATE_RCU_HEAD_READY,
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STATE_RCU_HEAD_QUEUED);
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return r1;
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}
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static inline void debug_rcu_head_unqueue(struct rcu_head *head)
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{
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debug_object_active_state(head, &rcuhead_debug_descr,
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STATE_RCU_HEAD_QUEUED,
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STATE_RCU_HEAD_READY);
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debug_object_deactivate(head, &rcuhead_debug_descr);
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}
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#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
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static inline int debug_rcu_head_queue(struct rcu_head *head)
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{
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return 0;
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}
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static inline void debug_rcu_head_unqueue(struct rcu_head *head)
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{
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}
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#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
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extern int rcu_cpu_stall_suppress_at_boot;
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static inline bool rcu_stall_is_suppressed_at_boot(void)
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{
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return rcu_cpu_stall_suppress_at_boot && !rcu_inkernel_boot_has_ended();
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}
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#ifdef CONFIG_RCU_STALL_COMMON
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extern int rcu_cpu_stall_ftrace_dump;
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extern int rcu_cpu_stall_suppress;
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extern int rcu_cpu_stall_timeout;
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int rcu_jiffies_till_stall_check(void);
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static inline bool rcu_stall_is_suppressed(void)
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{
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return rcu_stall_is_suppressed_at_boot() || rcu_cpu_stall_suppress;
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}
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#define rcu_ftrace_dump_stall_suppress() \
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do { \
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if (!rcu_cpu_stall_suppress) \
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rcu_cpu_stall_suppress = 3; \
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} while (0)
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#define rcu_ftrace_dump_stall_unsuppress() \
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do { \
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if (rcu_cpu_stall_suppress == 3) \
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rcu_cpu_stall_suppress = 0; \
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} while (0)
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#else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */
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static inline bool rcu_stall_is_suppressed(void)
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{
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return rcu_stall_is_suppressed_at_boot();
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}
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#define rcu_ftrace_dump_stall_suppress()
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#define rcu_ftrace_dump_stall_unsuppress()
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#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
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/*
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* Strings used in tracepoints need to be exported via the
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* tracing system such that tools like perf and trace-cmd can
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* translate the string address pointers to actual text.
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*/
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#define TPS(x) tracepoint_string(x)
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/*
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* Dump the ftrace buffer, but only one time per callsite per boot.
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*/
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#define rcu_ftrace_dump(oops_dump_mode) \
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do { \
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static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
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\
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if (!atomic_read(&___rfd_beenhere) && \
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!atomic_xchg(&___rfd_beenhere, 1)) { \
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tracing_off(); \
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rcu_ftrace_dump_stall_suppress(); \
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ftrace_dump(oops_dump_mode); \
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rcu_ftrace_dump_stall_unsuppress(); \
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} \
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} while (0)
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void rcu_early_boot_tests(void);
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void rcu_test_sync_prims(void);
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/*
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* This function really isn't for public consumption, but RCU is special in
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* that context switches can allow the state machine to make progress.
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*/
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extern void resched_cpu(int cpu);
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#if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU)
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#include <linux/rcu_node_tree.h>
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extern int rcu_num_lvls;
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extern int num_rcu_lvl[];
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extern int rcu_num_nodes;
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static bool rcu_fanout_exact;
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static int rcu_fanout_leaf;
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/*
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* Compute the per-level fanout, either using the exact fanout specified
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* or balancing the tree, depending on the rcu_fanout_exact boot parameter.
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*/
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static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
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{
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int i;
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for (i = 0; i < RCU_NUM_LVLS; i++)
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levelspread[i] = INT_MIN;
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if (rcu_fanout_exact) {
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levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
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for (i = rcu_num_lvls - 2; i >= 0; i--)
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levelspread[i] = RCU_FANOUT;
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} else {
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int ccur;
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int cprv;
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cprv = nr_cpu_ids;
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for (i = rcu_num_lvls - 1; i >= 0; i--) {
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ccur = levelcnt[i];
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levelspread[i] = (cprv + ccur - 1) / ccur;
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cprv = ccur;
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}
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}
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}
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extern void rcu_init_geometry(void);
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/* Returns a pointer to the first leaf rcu_node structure. */
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#define rcu_first_leaf_node() (rcu_state.level[rcu_num_lvls - 1])
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/* Is this rcu_node a leaf? */
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#define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1)
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/* Is this rcu_node the last leaf? */
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#define rcu_is_last_leaf_node(rnp) ((rnp) == &rcu_state.node[rcu_num_nodes - 1])
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/*
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* Do a full breadth-first scan of the {s,}rcu_node structures for the
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* specified state structure (for SRCU) or the only rcu_state structure
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* (for RCU).
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*/
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#define srcu_for_each_node_breadth_first(sp, rnp) \
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for ((rnp) = &(sp)->node[0]; \
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(rnp) < &(sp)->node[rcu_num_nodes]; (rnp)++)
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#define rcu_for_each_node_breadth_first(rnp) \
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srcu_for_each_node_breadth_first(&rcu_state, rnp)
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/*
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* Scan the leaves of the rcu_node hierarchy for the rcu_state structure.
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* Note that if there is a singleton rcu_node tree with but one rcu_node
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* structure, this loop -will- visit the rcu_node structure. It is still
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* a leaf node, even if it is also the root node.
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*/
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#define rcu_for_each_leaf_node(rnp) \
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for ((rnp) = rcu_first_leaf_node(); \
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(rnp) < &rcu_state.node[rcu_num_nodes]; (rnp)++)
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/*
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* Iterate over all possible CPUs in a leaf RCU node.
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*/
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#define for_each_leaf_node_possible_cpu(rnp, cpu) \
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for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
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(cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
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(cpu) <= rnp->grphi; \
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(cpu) = cpumask_next((cpu), cpu_possible_mask))
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/*
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* Iterate over all CPUs in a leaf RCU node's specified mask.
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*/
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#define rcu_find_next_bit(rnp, cpu, mask) \
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((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))
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#define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \
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for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
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(cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
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(cpu) <= rnp->grphi; \
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(cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))
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/*
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* Wrappers for the rcu_node::lock acquire and release.
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*
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* Because the rcu_nodes form a tree, the tree traversal locking will observe
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* different lock values, this in turn means that an UNLOCK of one level
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* followed by a LOCK of another level does not imply a full memory barrier;
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* and most importantly transitivity is lost.
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*
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* In order to restore full ordering between tree levels, augment the regular
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* lock acquire functions with smp_mb__after_unlock_lock().
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*
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* As ->lock of struct rcu_node is a __private field, therefore one should use
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* these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
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*/
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#define raw_spin_lock_rcu_node(p) \
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do { \
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raw_spin_lock(&ACCESS_PRIVATE(p, lock)); \
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smp_mb__after_unlock_lock(); \
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} while (0)
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#define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock))
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#define raw_spin_lock_irq_rcu_node(p) \
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do { \
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raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock)); \
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smp_mb__after_unlock_lock(); \
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} while (0)
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#define raw_spin_unlock_irq_rcu_node(p) \
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raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock))
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#define raw_spin_lock_irqsave_rcu_node(p, flags) \
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do { \
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raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
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smp_mb__after_unlock_lock(); \
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} while (0)
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#define raw_spin_unlock_irqrestore_rcu_node(p, flags) \
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raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)
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#define raw_spin_trylock_rcu_node(p) \
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({ \
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bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock)); \
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\
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if (___locked) \
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smp_mb__after_unlock_lock(); \
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___locked; \
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})
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#define raw_lockdep_assert_held_rcu_node(p) \
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lockdep_assert_held(&ACCESS_PRIVATE(p, lock))
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#endif /* #if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU) */
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#ifdef CONFIG_SRCU
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void srcu_init(void);
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#else /* #ifdef CONFIG_SRCU */
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static inline void srcu_init(void) { }
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#endif /* #else #ifdef CONFIG_SRCU */
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#ifdef CONFIG_TINY_RCU
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/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
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static inline bool rcu_gp_is_normal(void) { return true; }
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static inline bool rcu_gp_is_expedited(void) { return false; }
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static inline void rcu_expedite_gp(void) { }
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static inline void rcu_unexpedite_gp(void) { }
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static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }
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#else /* #ifdef CONFIG_TINY_RCU */
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bool rcu_gp_is_normal(void); /* Internal RCU use. */
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bool rcu_gp_is_expedited(void); /* Internal RCU use. */
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void rcu_expedite_gp(void);
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void rcu_unexpedite_gp(void);
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void rcupdate_announce_bootup_oddness(void);
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void show_rcu_tasks_gp_kthreads(void);
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void rcu_request_urgent_qs_task(struct task_struct *t);
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#endif /* #else #ifdef CONFIG_TINY_RCU */
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#define RCU_SCHEDULER_INACTIVE 0
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#define RCU_SCHEDULER_INIT 1
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#define RCU_SCHEDULER_RUNNING 2
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enum rcutorture_type {
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RCU_FLAVOR,
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RCU_TASKS_FLAVOR,
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RCU_TASKS_RUDE_FLAVOR,
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RCU_TASKS_TRACING_FLAVOR,
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RCU_TRIVIAL_FLAVOR,
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SRCU_FLAVOR,
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INVALID_RCU_FLAVOR
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};
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#if defined(CONFIG_TREE_RCU)
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void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
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unsigned long *gp_seq);
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void do_trace_rcu_torture_read(const char *rcutorturename,
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struct rcu_head *rhp,
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unsigned long secs,
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unsigned long c_old,
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unsigned long c);
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void rcu_gp_set_torture_wait(int duration);
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#else
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static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
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int *flags, unsigned long *gp_seq)
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{
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*flags = 0;
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*gp_seq = 0;
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}
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#ifdef CONFIG_RCU_TRACE
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void do_trace_rcu_torture_read(const char *rcutorturename,
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struct rcu_head *rhp,
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unsigned long secs,
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unsigned long c_old,
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unsigned long c);
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#else
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#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
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do { } while (0)
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#endif
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static inline void rcu_gp_set_torture_wait(int duration) { }
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#endif
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#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
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long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask);
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#endif
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#ifdef CONFIG_TINY_SRCU
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static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
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struct srcu_struct *sp, int *flags,
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unsigned long *gp_seq)
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{
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if (test_type != SRCU_FLAVOR)
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return;
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*flags = 0;
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*gp_seq = sp->srcu_idx;
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}
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#elif defined(CONFIG_TREE_SRCU)
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void srcutorture_get_gp_data(enum rcutorture_type test_type,
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struct srcu_struct *sp, int *flags,
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unsigned long *gp_seq);
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#endif
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#ifdef CONFIG_TINY_RCU
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static inline bool rcu_dynticks_zero_in_eqs(int cpu, int *vp) { return false; }
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static inline unsigned long rcu_get_gp_seq(void) { return 0; }
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static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
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static inline unsigned long
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srcu_batches_completed(struct srcu_struct *sp) { return 0; }
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static inline void rcu_force_quiescent_state(void) { }
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static inline void show_rcu_gp_kthreads(void) { }
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static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
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static inline void rcu_fwd_progress_check(unsigned long j) { }
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#else /* #ifdef CONFIG_TINY_RCU */
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bool rcu_dynticks_zero_in_eqs(int cpu, int *vp);
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unsigned long rcu_get_gp_seq(void);
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unsigned long rcu_exp_batches_completed(void);
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unsigned long srcu_batches_completed(struct srcu_struct *sp);
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void show_rcu_gp_kthreads(void);
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int rcu_get_gp_kthreads_prio(void);
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void rcu_fwd_progress_check(unsigned long j);
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void rcu_force_quiescent_state(void);
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extern struct workqueue_struct *rcu_gp_wq;
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extern struct workqueue_struct *rcu_par_gp_wq;
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#endif /* #else #ifdef CONFIG_TINY_RCU */
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#ifdef CONFIG_RCU_NOCB_CPU
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bool rcu_is_nocb_cpu(int cpu);
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void rcu_bind_current_to_nocb(void);
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#else
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static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
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static inline void rcu_bind_current_to_nocb(void) { }
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#endif
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#endif /* __LINUX_RCU_H */
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