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Do not spin when trying to lock on a single-CPU system.

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Reported by:	davidxu
This commit is contained in:
Jason Evans 2008-11-30 05:55:24 +00:00
parent cb2394085d
commit 93e34865fa
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=185468
1 changed files with 12 additions and 10 deletions
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22
lib/libc/stdlib/malloc.c
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@ -1262,18 +1262,20 @@ malloc_spin_lock(pthread_mutex_t *lock)
if (__isthreaded) {
if (_pthread_mutex_trylock(lock) != 0) {
unsigned i;
volatile unsigned j;
/* Exponentially back off if there are multiple CPUs. */
if (ncpus > 1) {
unsigned i;
volatile unsigned j;
/* Exponentially back off. */
for (i = 1; i <= SPIN_LIMIT_2POW; i++) {
for (j = 0; j < (1U << i); j++) {
ret++;
CPU_SPINWAIT;
for (i = 1; i <= SPIN_LIMIT_2POW; i++) {
for (j = 0; j < (1U << i); j++) {
ret++;
CPU_SPINWAIT;
}
if (_pthread_mutex_trylock(lock) == 0)
return (ret);
}
if (_pthread_mutex_trylock(lock) == 0)
return (ret);
}
/*