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s390/time: avoid races when updating tb_update_count 

The increment might not be atomic and we're not holding the
timekeeper_lock. Therefore we might lose an update to count, resulting in
VDSO being trapped in a loop. As other archs also simply update the
values and count doesn't seem to have an impact on reloading of these
values in VDSO code, let's just remove the update of tb_update_count.

Suggested-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
hifive-unleashed-5.1
David Hildenbrand 2016-07-18 17:10:17 +02:00 committed by Martin Schwidefsky
parent 0c00b1e00b
commit 67f03de5f0
1 changed files with 0 additions and 5 deletions
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5
arch/s390/kernel/time.c
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@ -278,13 +278,8 @@ extern struct timezone sys_tz;
void update_vsyscall_tz(void)
{
/* Make userspace gettimeofday spin until we're done. */
++vdso_data->tb_update_count;
smp_wmb();
vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
vdso_data->tz_dsttime = sys_tz.tz_dsttime;
smp_wmb();
++vdso_data->tb_update_count;
}
/*