From e5d4d1756b07d9490a0269a9e68c1e05ee1feb9b Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sat, 21 Mar 2020 12:25:58 +0100 Subject: timekeeping: Split jiffies seqlock seqlock consists of a sequence counter and a spinlock_t which is used to serialize the writers. spinlock_t is substituted by a "sleeping" spinlock on PREEMPT_RT enabled kernels which breaks the usage in the timekeeping code as the writers are executed in hard interrupt and therefore non-preemptible context even on PREEMPT_RT. The spinlock in seqlock cannot be unconditionally replaced by a raw_spinlock_t as many seqlock users have nesting spinlock sections or other code which is not suitable to run in truly atomic context on RT. Instead of providing a raw_seqlock API for a single use case, open code the seqlock for the jiffies use case and implement it with a raw_spinlock_t and a sequence counter. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200321113242.120587764@linutronix.de --- kernel/time/timekeeping.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/time/timekeeping.h') diff --git a/kernel/time/timekeeping.h b/kernel/time/timekeeping.h index 141ab3ab0354..099737f6f10c 100644 --- a/kernel/time/timekeeping.h +++ b/kernel/time/timekeeping.h @@ -25,7 +25,8 @@ static inline void sched_clock_resume(void) { } extern void do_timer(unsigned long ticks); extern void update_wall_time(void); -extern seqlock_t jiffies_lock; +extern raw_spinlock_t jiffies_lock; +extern seqcount_t jiffies_seq; #define CS_NAME_LEN 32 -- cgit v1.2.3