From cde9070d9970eef1f7ec2360586c802a16230ad8 Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Fri, 10 May 2024 07:43:50 +0000
Subject: [PATCH] rtl88x2CE_WiFi_linux driver
---
kernel/kernel/time/posix-timers.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 41 insertions(+), 8 deletions(-)
diff --git a/kernel/kernel/time/posix-timers.c b/kernel/kernel/time/posix-timers.c
index b624788..6d12a72 100644
--- a/kernel/kernel/time/posix-timers.c
+++ b/kernel/kernel/time/posix-timers.c
@@ -846,6 +846,10 @@
rcu_read_lock();
unlock_timer(timer, *flags);
+ /*
+ * kc->timer_wait_running() might drop RCU lock. So @timer
+ * cannot be touched anymore after the function returns!
+ */
if (!WARN_ON_ONCE(!kc->timer_wait_running))
kc->timer_wait_running(timer);
@@ -1033,27 +1037,52 @@
}
/*
- * return timer owned by the process, used by exit_itimers
+ * Delete a timer if it is armed, remove it from the hash and schedule it
+ * for RCU freeing.
*/
static void itimer_delete(struct k_itimer *timer)
{
-retry_delete:
- spin_lock_irq(&timer->it_lock);
+ unsigned long flags;
+ /*
+ * irqsave is required to make timer_wait_running() work.
+ */
+ spin_lock_irqsave(&timer->it_lock, flags);
+
+retry_delete:
+ /*
+ * Even if the timer is not longer accessible from other tasks
+ * it still might be armed and queued in the underlying timer
+ * mechanism. Worse, that timer mechanism might run the expiry
+ * function concurrently.
+ */
if (timer_delete_hook(timer) == TIMER_RETRY) {
- spin_unlock_irq(&timer->it_lock);
+ /*
+ * Timer is expired concurrently, prevent livelocks
+ * and pointless spinning on RT.
+ *
+ * timer_wait_running() drops timer::it_lock, which opens
+ * the possibility for another task to delete the timer.
+ *
+ * That's not possible here because this is invoked from
+ * do_exit() only for the last thread of the thread group.
+ * So no other task can access and delete that timer.
+ */
+ if (WARN_ON_ONCE(timer_wait_running(timer, &flags) != timer))
+ return;
+
goto retry_delete;
}
list_del(&timer->list);
- spin_unlock_irq(&timer->it_lock);
+ spin_unlock_irqrestore(&timer->it_lock, flags);
release_posix_timer(timer, IT_ID_SET);
}
/*
- * This is called by do_exit or de_thread, only when nobody else can
- * modify the signal->posix_timers list. Yet we need sighand->siglock
- * to prevent the race with /proc/pid/timers.
+ * Invoked from do_exit() when the last thread of a thread group exits.
+ * At that point no other task can access the timers of the dying
+ * task anymore.
*/
void exit_itimers(struct task_struct *tsk)
{
@@ -1063,10 +1092,12 @@
if (list_empty(&tsk->signal->posix_timers))
return;
+ /* Protect against concurrent read via /proc/$PID/timers */
spin_lock_irq(&tsk->sighand->siglock);
list_replace_init(&tsk->signal->posix_timers, &timers);
spin_unlock_irq(&tsk->sighand->siglock);
+ /* The timers are not longer accessible via tsk::signal */
while (!list_empty(&timers)) {
tmr = list_first_entry(&timers, struct k_itimer, list);
itimer_delete(tmr);
@@ -1270,6 +1301,7 @@
return -EINVAL;
if (flags & TIMER_ABSTIME)
rmtp = NULL;
+ current->restart_block.fn = do_no_restart_syscall;
current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
current->restart_block.nanosleep.rmtp = rmtp;
@@ -1297,6 +1329,7 @@
return -EINVAL;
if (flags & TIMER_ABSTIME)
rmtp = NULL;
+ current->restart_block.fn = do_no_restart_syscall;
current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
current->restart_block.nanosleep.compat_rmtp = rmtp;
--
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