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[S390] etr: Add barrier() to etr_sync_cpu_start().

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Force reading of *in_sync in while loop. Loops where the content that
is checked for is changed by a different cpu always should have some
sort of barrier() semantics.
Otherwise this might lead to very subtle bugs.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2007-02-21 10:55:15 +01:00 • committed by Martin Schwidefsky
parent 118bcd31b3
commit 6c732de2d3
1 changed files with 9 additions and 1 deletions
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10
arch/s390/kernel/time.c
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@ -747,6 +747,7 @@ static void etr_adjust_time(unsigned long long clock, unsigned long long delay)
} }
} }
#ifdef CONFIG_SMP
static void etr_sync_cpu_start(void *dummy) static void etr_sync_cpu_start(void *dummy)
{ {
int *in_sync = dummy; int *in_sync = dummy;
@ -758,8 +759,14 @@ static void etr_sync_cpu_start(void *dummy)
* __udelay will stop the cpu on an enabled wait psw until the * __udelay will stop the cpu on an enabled wait psw until the
* TOD is running again. * TOD is running again.
*/ */
while (*in_sync == 0) while (*in_sync == 0) {
__udelay(1); __udelay(1);
/*
* A different cpu changes *in_sync. Therefore use
* barrier() to force memory access.
*/
barrier();
}
if (*in_sync != 1) if (*in_sync != 1)
/* Didn't work. Clear per-cpu in sync bit again. */ /* Didn't work. Clear per-cpu in sync bit again. */
etr_disable_sync_clock(NULL); etr_disable_sync_clock(NULL);
@ -773,6 +780,7 @@ static void etr_sync_cpu_start(void *dummy)
static void etr_sync_cpu_end(void *dummy) static void etr_sync_cpu_end(void *dummy)
{ {
} }
#endif /* CONFIG_SMP */
/* /*
* Sync the TOD clock using the port refered to by aibp. This port * Sync the TOD clock using the port refered to by aibp. This port