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![]() Use try_cmpxchg() instead of cmpxchg(*ptr, old, new) == old. The x86 CMPXCHG instruction returns success in the ZF flag, so this change saves a compare after CMPXCHG (and related move instruction in front of CMPXCHG). Also, try_cmpxchg() implicitly assigns old *ptr value to "old" when CMPXCHG fails. There is no need to re-read the value in the loop. Note that the value from *ptr should be read using READ_ONCE() to prevent the compiler from merging, refetching or reordering the read. No functional change intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Waiman Long <longman@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20240124104953.612063-1-ubizjak@gmail.com |
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.. | ||
irqflag-debug.c | ||
lock_events.c | ||
lock_events.h | ||
lock_events_list.h | ||
lockdep.c | ||
lockdep_internals.h | ||
lockdep_proc.c | ||
lockdep_states.h | ||
locktorture.c | ||
Makefile | ||
mcs_spinlock.h | ||
mutex-debug.c | ||
mutex.c | ||
mutex.h | ||
osq_lock.c | ||
percpu-rwsem.c | ||
qrwlock.c | ||
qspinlock.c | ||
qspinlock_paravirt.h | ||
qspinlock_stat.h | ||
rtmutex.c | ||
rtmutex_api.c | ||
rtmutex_common.h | ||
rwbase_rt.c | ||
rwsem.c | ||
semaphore.c | ||
spinlock.c | ||
spinlock_debug.c | ||
spinlock_rt.c | ||
test-ww_mutex.c | ||
ww_mutex.h | ||
ww_rt_mutex.c |