diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2023-01-16 17:53:37 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2023-02-06 14:22:09 +0100 |
| commit | 915d4ad3830aa1a2dafda9b737749fb410cb9790 (patch) | |
| tree | e8287c524625634c219ad3dc4e553a1d429bdcec /kernel/time | |
| parent | cbdb1f163af2bb90d01be1f0263df1d8d5c9d9d3 (diff) | |
| download | linux-915d4ad3830aa1a2dafda9b737749fb410cb9790.tar.gz | |
posix-timers: Use atomic64_try_cmpxchg() in __update_gt_cputime()
Use atomic64_try_cmpxchg() instead of atomic64_cmpxchg() in
__update_gt_cputime(). The x86 CMPXCHG instruction returns success in ZF
flag, so this change saves a compare after cmpxchg() (and related move
instruction in front of cmpxchg()).
Also, atomic64_try_cmpxchg() implicitly assigns old *ptr value to "old"
when cmpxchg() fails. There is no need to re-read the value in the loop.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230116165337.5810-1-ubizjak@gmail.com
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/posix-cpu-timers.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index cb925e8ef9a8b..2f5e9b34022c5 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -243,13 +243,12 @@ static void proc_sample_cputime_atomic(struct task_cputime_atomic *at, */ static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime) { - u64 curr_cputime; -retry: - curr_cputime = atomic64_read(cputime); - if (sum_cputime > curr_cputime) { - if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime) - goto retry; - } + u64 curr_cputime = atomic64_read(cputime); + + do { + if (sum_cputime <= curr_cputime) + return; + } while (!atomic64_try_cmpxchg(cputime, &curr_cputime, sum_cputime)); } static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, |