From 1b44e98d7d0754bbcf0222baf179f5e2e3dbea7b Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Mon, 7 Nov 2005 00:59:02 -0800 Subject: [PATCH] [PATCH] s390: stop_hz_timer vs. xtime updates The calculation of the value return by next_timer_interrupt from jiffies to jiffies_64 is racy against xtime updates. We need to protect the calculation with read_seqbegin/read_seqretry. Signed-off-by: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/s390/kernel/time.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index 9a1d958..c36353e 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -237,6 +237,8 @@ int sysctl_hz_timer = 1; */ static inline void stop_hz_timer(void) { + unsigned long flags; + unsigned long seq, next; __u64 timer, todval; if (sysctl_hz_timer != 0) @@ -257,7 +259,11 @@ static inline void stop_hz_timer(void) * This cpu is going really idle. Set up the clock comparator * for the next event. */ - timer = (__u64) (next_timer_interrupt() - jiffies) + jiffies_64; + next = next_timer_interrupt(); + do { + seq = read_seqbegin_irqsave(&xtime_lock, flags); + timer = (__u64)(next - jiffies) + jiffies_64; + } while (read_seqretry_irqrestore(&xtime_lock, seq, flags)); todval = -1ULL; /* Be careful about overflows. */ if (timer < (-1ULL / CLK_TICKS_PER_JIFFY)) { -- 2.7.4