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| author | Thomas Gleixner <tglx@linutronix.de> | 2020-03-21 12:25:58 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-03-21 16:00:23 +0100 |
| commit | e5d4d1756b07d9490a0269a9e68c1e05ee1feb9b (patch) | |
| tree | 27a6cf91053169846adab85b04a84cb9e763d2fb /kernel/time/timekeeping.h | |
| parent | 919e9e6395cfac23b7e71ed88930367459055daf (diff) | |
| download | linux-e5d4d1756b07d9490a0269a9e68c1e05ee1feb9b.tar.bz2 | |
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 <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.120587764@linutronix.de
Diffstat (limited to 'kernel/time/timekeeping.h')
| -rw-r--r-- | kernel/time/timekeeping.h | 3 |
1 files changed, 2 insertions, 1 deletions
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 |