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authorJohn Stultz <john.stultz@linaro.org>2016-08-23 16:08:21 -0700
committerThomas Gleixner <tglx@linutronix.de>2016-08-24 09:34:31 +0200
commit27727df240c7cc84f2ba6047c6f18d5addfd25ef (patch)
tree92bc0d5823e29fc5ea10c1707e80bebada834660
parentfa8410b355251fd30341662a40ac6b22d3e38468 (diff)
timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING
When I added some extra sanity checking in timekeeping_get_ns() under CONFIG_DEBUG_TIMEKEEPING, I missed that the NMI safe __ktime_get_fast_ns() method was using timekeeping_get_ns(). Thus the locking added to the debug checks broke the NMI-safety of __ktime_get_fast_ns(). This patch open-codes the timekeeping_get_ns() logic for __ktime_get_fast_ns(), so can avoid any deadlocks in NMI. Fixes: 4ca22c2648f9 "timekeeping: Add warnings when overflows or underflows are observed" Reported-by: Steven Rostedt <rostedt@goodmis.org> Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: John Stultz <john.stultz@linaro.org> Cc: stable <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/1471993702-29148-2-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--kernel/time/timekeeping.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 3b65746c7f15..e07fb093f819 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -401,7 +401,10 @@ static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
do {
seq = raw_read_seqcount_latch(&tkf->seq);
tkr = tkf->base + (seq & 0x01);
- now = ktime_to_ns(tkr->base) + timekeeping_get_ns(tkr);
+ now = ktime_to_ns(tkr->base);
+
+ now += clocksource_delta(tkr->read(tkr->clock),
+ tkr->cycle_last, tkr->mask);
} while (read_seqcount_retry(&tkf->seq, seq));
return now;