forked from rpms/glibc
34 lines
1.1 KiB
Diff
34 lines
1.1 KiB
Diff
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commit a2e259014f8a0e5f3ff938314f3087b74255804d
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Author: H.J. Lu <hjl.tools@gmail.com>
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Date: Thu Nov 11 06:31:51 2021 -0800
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Avoid extra load with CAS in __pthread_mutex_lock_full [BZ #28537]
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Replace boolean CAS with value CAS to avoid the extra load.
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Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
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(cherry picked from commit 0b82747dc48d5bf0871bdc6da8cb6eec1256355f)
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diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
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index da624f322d06d0ee..a04e0158451c8fff 100644
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--- a/nptl/pthread_mutex_lock.c
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+++ b/nptl/pthread_mutex_lock.c
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@@ -298,12 +298,12 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
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meantime. */
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if ((oldval & FUTEX_WAITERS) == 0)
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{
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- if (atomic_compare_and_exchange_bool_acq (&mutex->__data.__lock,
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- oldval | FUTEX_WAITERS,
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- oldval)
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- != 0)
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+ int val;
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+ if ((val = atomic_compare_and_exchange_val_acq
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+ (&mutex->__data.__lock, oldval | FUTEX_WAITERS,
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+ oldval)) != oldval)
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{
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- oldval = mutex->__data.__lock;
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+ oldval = val;
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continue;
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}
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oldval |= FUTEX_WAITERS;
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