diff options
Diffstat (limited to 'debian/patches-rt/0345-timers-Don-t-block-on-expiry_lock-for-TIMER_IRQSAFE-.patch')
| -rw-r--r-- | debian/patches-rt/0345-timers-Don-t-block-on-expiry_lock-for-TIMER_IRQSAFE-.patch | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/debian/patches-rt/0345-timers-Don-t-block-on-expiry_lock-for-TIMER_IRQSAFE-.patch b/debian/patches-rt/0345-timers-Don-t-block-on-expiry_lock-for-TIMER_IRQSAFE-.patch new file mode 100644 index 000000000..c7a563449 --- /dev/null +++ b/debian/patches-rt/0345-timers-Don-t-block-on-expiry_lock-for-TIMER_IRQSAFE-.patch @@ -0,0 +1,68 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Mon, 24 Oct 2022 10:17:22 +0200 +Subject: [PATCH 345/351] timers: Don't block on ->expiry_lock for + TIMER_IRQSAFE timers +Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=9841dc5af8b334fa1a9f4c0e9acde4a0b3839d6f + +Upstream commit c725dafc95f1b37027840aaeaa8b7e4e9cd20516 + +PREEMPT_RT does not spin and wait until a running timer completes its +callback but instead it blocks on a sleeping lock to prevent a livelock in +the case that the task waiting for the callback completion preempted the +callback. + +This cannot be done for timers flagged with TIMER_IRQSAFE. These timers can +be canceled from an interrupt disabled context even on RT kernels. + +The expiry callback of such timers is invoked with interrupts disabled so +there is no need to use the expiry lock mechanism because obviously the +callback cannot be preempted even on RT kernels. + +Do not use the timer_base::expiry_lock mechanism when waiting for a running +callback to complete if the timer is flagged with TIMER_IRQSAFE. + +Also add a lockdep assertion for RT kernels to validate that the expiry +lock mechanism is always invoked in preemptible context. + +Reported-by: Mike Galbraith <efault@gmx.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Link: https://lore.kernel.org/r/20201103190937.hga67rqhvknki3tp@linutronix.de +[bigeasy: The logic in v4.19 is slightly different but the outcome is the + same as we must not sleep while waiting for the irqsafe timer to + complete. The IRQSAFE timer can not be preempted. + The "lockdep annotation" is not available and has been replaced with + might_sleep()] +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Signed-off-by: Daniel Wagner <wagi@monom.org> +--- + kernel/time/timer.c | 9 +++++++++ + 1 file changed, 9 insertions(+) + +diff --git a/kernel/time/timer.c b/kernel/time/timer.c +index 3e2c0bd03004..0a6d60b3e67c 100644 +--- a/kernel/time/timer.c ++++ b/kernel/time/timer.c +@@ -1272,6 +1272,9 @@ static int __del_timer_sync(struct timer_list *timer) + if (ret >= 0) + return ret; + ++ if (READ_ONCE(timer->flags) & TIMER_IRQSAFE) ++ continue; ++ + /* + * When accessing the lock, timers of base are no longer expired + * and so timer is no longer running. +@@ -1336,6 +1339,12 @@ int del_timer_sync(struct timer_list *timer) + * could lead to deadlock. + */ + WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE)); ++ /* ++ * Must be able to sleep on PREEMPT_RT because of the slowpath in ++ * __del_timer_sync(). ++ */ ++ if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE)) ++ might_sleep(); + + return __del_timer_sync(timer); + } |