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| author | Thomas Gleixner <tglx@linutronix.de> | 2020-03-21 12:25:58 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-05-17 11:35:39 +0200 |
| commit | a23607579f12bc792fa4327544775afe428ac826 (patch) | |
| tree | 7a5aec35a4edbc5d8a8846fdd9e10db13f2bc8a2 /kernel/time/tick-common.c | |
| parent | 22d7ec50ffdd49288b17a52f7fe2312e9dbd0390 (diff) | |
| download | linux-a23607579f12bc792fa4327544775afe428ac826.tar.gz linux-a23607579f12bc792fa4327544775afe428ac826.tar.bz2 linux-a23607579f12bc792fa4327544775afe428ac826.zip | |
timekeeping: Split jiffies seqlock
[ Upstream commit e5d4d1756b07d9490a0269a9e68c1e05ee1feb9b ]
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
Stable-dep-of: e9523a0d8189 ("tick/common: Align tick period with the HZ tick.")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel/time/tick-common.c')
| -rw-r--r-- | kernel/time/tick-common.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 7e5d3524e924..6c9c342dd0e5 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -84,13 +84,15 @@ int tick_is_oneshot_available(void) static void tick_periodic(int cpu) { if (tick_do_timer_cpu == cpu) { - write_seqlock(&jiffies_lock); + raw_spin_lock(&jiffies_lock); + write_seqcount_begin(&jiffies_seq); /* Keep track of the next tick event */ tick_next_period = ktime_add(tick_next_period, tick_period); do_timer(1); - write_sequnlock(&jiffies_lock); + write_seqcount_end(&jiffies_seq); + raw_spin_unlock(&jiffies_lock); update_wall_time(); } @@ -162,9 +164,9 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast) ktime_t next; do { - seq = read_seqbegin(&jiffies_lock); + seq = read_seqcount_begin(&jiffies_seq); next = tick_next_period; - } while (read_seqretry(&jiffies_lock, seq)); + } while (read_seqcount_retry(&jiffies_seq, seq)); clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); |