From: Heiko Carstens <[email protected]>
[S390] etr: Add barrier() to etr_sync_cpu_start().
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 <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>
---
arch/s390/kernel/time.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletion(-)
diff -urpN linux-2.6/arch/s390/kernel/time.c linux-2.6-patched/arch/s390/kernel/time.c
--- linux-2.6/arch/s390/kernel/time.c 2007-02-21 10:47:06.000000000 +0100
+++ linux-2.6-patched/arch/s390/kernel/time.c 2007-02-21 10:47:28.000000000 +0100
@@ -747,6 +747,7 @@ static void etr_adjust_time(unsigned lon
}
}
+#ifdef CONFIG_SMP
static void etr_sync_cpu_start(void *dummy)
{
int *in_sync = dummy;
@@ -758,8 +759,14 @@ static void etr_sync_cpu_start(void *dum
* __udelay will stop the cpu on an enabled wait psw until the
* TOD is running again.
*/
- while (*in_sync == 0)
+ while (*in_sync == 0) {
__udelay(1);
+ /*
+ * A different cpu changes *in_sync. Therefore use
+ * barrier() to force memory access.
+ */
+ barrier();
+ }
if (*in_sync != 1)
/* Didn't work. Clear per-cpu in sync bit again. */
etr_disable_sync_clock(NULL);
@@ -773,6 +780,7 @@ static void etr_sync_cpu_start(void *dum
static void etr_sync_cpu_end(void *dummy)
{
}
+#endif /* CONFIG_SMP */
/*
* Sync the TOD clock using the port refered to by aibp. This port
--
blue skies, IBM Deutschland Entwicklung GmbH
Martin Vorsitzender des Aufsichtsrats: Johann Weihen
Geschäftsführung: Herbert Kircher
Martin Schwidefsky Sitz der Gesellschaft: Böblingen
Linux on zSeries Registergericht: Amtsgericht Stuttgart,
Development HRB 243294
"Reality continues to ruin my life." - Calvin.
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