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. Cc: Steven Rostedt <rost...@goodmis.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Ingo Molnar <mi...@kernel.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: stable <sta...@vger.kernel.org> # 4.1+ Reported-by: Steven Rostedt <rost...@goodmis.org> Reported-by: Peter Zijlstra <pet...@infradead.org> Signed-off-by: John Stultz <john.stu...@linaro.org> --- kernel/time/timekeeping.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 3b65746..e07fb09 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; -- 1.9.1