Messages in this thread | | | Date | Fri, 17 Oct 2014 13:23:12 -0400 | From | Prarit Bhargava <> | Subject | Re: [PATCH] clocksource, Add warning to clocksource_delta() validation code |
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On 10/17/2014 09:57 AM, Prarit Bhargava wrote: > A bug report came in against an older kernel which output "backward time" > messages and the report noted that the upstream kernel worked. After some > investigation it turned out that one of the sockets was bad on the system > and the "backward time" messages were caused by a real, but intermittent, > hardware failure. > > Commit 09ec54429c6d10f87d1f084de53ae2c1c3a81108 ("clocksource: Move > cycle_last validation to core code") modifies the x86 clocksource such that > if a negative delta between two reads of time is calculated the > clocksource_delta() code will return 0. There is no warning when this > occurs and there really should be one in order to catch not only hardware > issues like the issue above, but potential coding issues as the code is > modified. This patch introduces a WARN() which will also dump a stack > trace to the console so the exact code path can be evaluated. > > I tested this by booting on the broken hardware and left the system idle > until a negative clocksource_delta() event occurred. > > Cc: John Stultz <john.stultz@linaro.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Sorry everyone -- I accidentally sent this out. It is still untested and needs some bake time.
Please ignore this patch.
P.
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