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Commit 6c732de2 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
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[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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 118bcd31

arch/s390/kernel/time.c

+9 −1
Original line number Diff line number Diff line
@@ -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)

{

	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

	 * 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 *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