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authorUros Bizjak <ubizjak@gmail.com>2023-01-16 17:53:37 +0100
committerThomas Gleixner <tglx@linutronix.de>2023-02-06 14:22:09 +0100
commit915d4ad3830aa1a2dafda9b737749fb410cb9790 (patch)
treee8287c524625634c219ad3dc4e553a1d429bdcec /kernel/time
parentcbdb1f163af2bb90d01be1f0263df1d8d5c9d9d3 (diff)
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.c13
1 files changed, 6 insertions, 7 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index cb925e8ef9a8..2f5e9b34022c 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,