From: Greg Kroah-Hartman Date: Thu, 13 Oct 2016 15:01:46 +0000 (+0200) Subject: 4.8-stable patches X-Git-Tag: v4.4.25~11 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7b601529105963c6310fc9d131dabc18752ca3c5;p=thirdparty%2Fkernel%2Fstable-queue.git 4.8-stable patches added patches: timekeeping-fix-__ktime_get_fast_ns-regression.patch --- diff --git a/queue-4.8/series b/queue-4.8/series index f448b59aba8..66ec5d14397 100644 --- a/queue-4.8/series +++ b/queue-4.8/series @@ -1 +1,2 @@ usb-storage-fix-runtime-pm-issue-in-usb_stor_probe2.patch +timekeeping-fix-__ktime_get_fast_ns-regression.patch diff --git a/queue-4.8/timekeeping-fix-__ktime_get_fast_ns-regression.patch b/queue-4.8/timekeeping-fix-__ktime_get_fast_ns-regression.patch new file mode 100644 index 00000000000..75291b27b5e --- /dev/null +++ b/queue-4.8/timekeeping-fix-__ktime_get_fast_ns-regression.patch @@ -0,0 +1,84 @@ +From 58bfea9532552d422bde7afa207e1a0f08dffa7d Mon Sep 17 00:00:00 2001 +From: John Stultz +Date: Tue, 4 Oct 2016 19:55:48 -0700 +Subject: timekeeping: Fix __ktime_get_fast_ns() regression + +From: John Stultz + +commit 58bfea9532552d422bde7afa207e1a0f08dffa7d upstream. + +In commit 27727df240c7 ("Avoid taking lock in NMI path with +CONFIG_DEBUG_TIMEKEEPING"), I changed the logic to open-code +the timekeeping_get_ns() function, but I forgot to include +the unit conversion from cycles to nanoseconds, breaking the +function's output, which impacts users like perf. + +This results in bogus perf timestamps like: + swapper 0 [000] 253.427536: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.426573: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.426687: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.426800: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.426905: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.427022: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.427127: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.427239: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.427346: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 254.427463: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 255.426572: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + +Instead of more reasonable expected timestamps like: + swapper 0 [000] 39.953768: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.064839: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.175956: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.287103: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.398217: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.509324: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.620437: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.731546: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.842654: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 40.953772: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + swapper 0 [000] 41.064881: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms]) + +Add the proper use of timekeeping_delta_to_ns() to convert +the cycle delta to nanoseconds as needed. + +Thanks to Brendan and Alexei for finding this quickly after +the v4.8 release. Unfortunately the problematic commit has +landed in some -stable trees so they'll need this fix as +well. + +Many apologies for this mistake. I'll be looking to add a +perf-clock sanity test to the kselftest timers tests soon. + +Fixes: 27727df240c7 "timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING" +Reported-by: Brendan Gregg +Reported-by: Alexei Starovoitov +Tested-and-reviewed-by: Mathieu Desnoyers +Signed-off-by: John Stultz +Cc: Peter Zijlstra +Cc: Steven Rostedt +Link: http://lkml.kernel.org/r/1475636148-26539-1-git-send-email-john.stultz@linaro.org +Signed-off-by: Thomas Gleixner +Cc: Mathieu Desnoyers +Signed-off-by: Greg Kroah-Hartman + +--- + kernel/time/timekeeping.c | 7 +++++-- + 1 file changed, 5 insertions(+), 2 deletions(-) + +--- a/kernel/time/timekeeping.c ++++ b/kernel/time/timekeeping.c +@@ -403,8 +403,11 @@ static __always_inline u64 __ktime_get_f + tkr = tkf->base + (seq & 0x01); + now = ktime_to_ns(tkr->base); + +- now += clocksource_delta(tkr->read(tkr->clock), +- tkr->cycle_last, tkr->mask); ++ now += timekeeping_delta_to_ns(tkr, ++ clocksource_delta( ++ tkr->read(tkr->clock), ++ tkr->cycle_last, ++ tkr->mask)); + } while (read_seqcount_retry(&tkf->seq, seq)); + + return now;