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nptl: Effectively skip CAS in spinlock loop
The commit:
"Add LLL_MUTEX_READ_LOCK [BZ #28537]"
SHA1: d672a98a1a
introduced LLL_MUTEX_READ_LOCK, to skip CAS in spinlock loop
if atomic load fails. But, "continue" inside of do-while loop
does not skip the evaluation of escape expression, thus CAS
is not skipped.
Replace do-while with while and skip LLL_MUTEX_TRYLOCK if
LLL_MUTEX_READ_LOCK fails.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
parent
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commit
6b8dbbd03a
@ -146,10 +146,9 @@ 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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