diff options
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/jiffies.c | |
parent | 919e9e6395cfac23b7e71ed88930367459055daf (diff) |
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/jiffies.c')
-rw-r--r-- | kernel/time/jiffies.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c index d23b434c2ca7..eddcf4970444 100644 --- a/kernel/time/jiffies.c +++ b/kernel/time/jiffies.c @@ -58,7 +58,8 @@ static struct clocksource clocksource_jiffies = { .max_cycles = 10, }; -__cacheline_aligned_in_smp DEFINE_SEQLOCK(jiffies_lock); +__cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(jiffies_lock); +__cacheline_aligned_in_smp seqcount_t jiffies_seq; #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void) @@ -67,9 +68,9 @@ u64 get_jiffies_64(void) u64 ret; do { - seq = read_seqbegin(&jiffies_lock); + seq = read_seqcount_begin(&jiffies_seq); ret = jiffies_64; - } while (read_seqretry(&jiffies_lock, seq)); + } while (read_seqcount_retry(&jiffies_seq, seq)); return ret; } EXPORT_SYMBOL(get_jiffies_64); |