From 67f03de5f0ad6b4b0481bb43e4a819d1a441900b Mon Sep 17 00:00:00 2001
From: David Hildenbrand <dahi@linux.vnet.ibm.com>
Date: Mon, 18 Jul 2016 17:10:17 +0200
Subject: 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>
---
arch/s390/kernel/time.c | 5 -----
1 file changed, 5 deletions(-)
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 5b1a199667e2..0bfcc492987e 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -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;
}
/*
--
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