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39 lines
1.3 KiB
39 lines
1.3 KiB
1 year ago
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commit 43760d33d78f9ea8c8af942b570112ee801b99df
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Author: Jangwoong Kim <6812skiii@gmail.com>
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Date: Tue Dec 14 21:30:51 2021 +0900
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nptl: Effectively skip CAS in spinlock loop
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The commit:
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"Add LLL_MUTEX_READ_LOCK [BZ #28537]"
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SHA1: d672a98a1af106bd68deb15576710cd61363f7a6
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introduced LLL_MUTEX_READ_LOCK, to skip CAS in spinlock loop
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if atomic load fails. But, "continue" inside of do-while loop
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does not skip the evaluation of escape expression, thus CAS
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is not skipped.
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Replace do-while with while and skip LLL_MUTEX_TRYLOCK if
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LLL_MUTEX_READ_LOCK fails.
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Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
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(cherry picked from commit 6b8dbbd03ac88f169b65b5c7d7278576a11d2e44)
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diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
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index 49901ffa0a96d659..bbe754a272b97d91 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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@@ -147,10 +147,9 @@ PTHREAD_MUTEX_LOCK (pthread_mutex_t *mutex)
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break;
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}
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atomic_spin_nop ();
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- if (LLL_MUTEX_READ_LOCK (mutex) != 0)
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- continue;
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}
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- while (LLL_MUTEX_TRYLOCK (mutex) != 0);
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+ while (LLL_MUTEX_READ_LOCK (mutex) != 0
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+ || LLL_MUTEX_TRYLOCK (mutex) != 0);
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mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
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}
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