From a5dec9f82ab2ae486119f0b0820ea16db3e522c3 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 26 Jul 2021 14:55:08 +0200 Subject: posix-cpu-timers: Assert task sighand is locked while starting cputime counter Starting the process wide cputime counter needs to be done in the same sighand locking sequence than actually arming the related timer otherwise this races against concurrent timers setting/expiring in the same threadgroup. Detecting that the cputime counter is started without holding the sighand lock is a first step toward debugging such situations. Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Frederic Weisbecker Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210726125513.271824-2-frederic@kernel.org --- kernel/time/posix-cpu-timers.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel/time') diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 517be7fd175e..4693d3c71e7e 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -291,6 +291,8 @@ static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples) struct thread_group_cputimer *cputimer = &tsk->signal->cputimer; struct posix_cputimers *pct = &tsk->signal->posix_cputimers; + lockdep_assert_task_sighand_held(tsk); + /* Check if cputimer isn't running. This is accessed without locking. */ if (!READ_ONCE(pct->timers_active)) { struct task_cputime sum; -- cgit