From mboxrd@z Thu Jan 1 00:00:00 1970 From: john.stultz@linaro.org (John Stultz) Date: Thu, 02 Jan 2014 12:30:12 -0800 Subject: v3.13-rc6+ regression (ARM board) In-Reply-To: <52C5C5F6.70803@linaro.org> References: <20131231104511.GA9688@1wt.eu> <20140102101455.GG10158@pengutronix.de> <52C5C5F6.70803@linaro.org> Message-ID: <52C5CC54.4050602@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 01/02/2014 12:03 PM, John Stultz wrote: > On 01/02/2014 11:38 AM, Linus Torvalds wrote: >> On Thu, Jan 2, 2014 at 4:07 AM, Krzysztof Ha?asa wrote: >>> This means these two commits don't like each other: >>> >>> seqcount: Add lockdep functionality to seqcount/seqlock structures >>> sched_clock: Use seqcount instead of rolling our own >> Does something like this fix it for you? >> >> --- a/kernel/time/sched_clock.c >> +++ b/kernel/time/sched_clock.c >> @@ -36,6 +36,7 @@ core_param(irqtime, irqtime, int, 0400); >> >> static struct clock_data cd = { >> .mult = NSEC_PER_SEC / HZ, >> + .seq = SEQCNT_ZERO(cd.seq), >> }; >> >> static u64 __read_mostly sched_clock_mask; >> >> (The above is not even compile-tested, because x86 doesn't use >> GENERIC_SCHED_CLOCK. So I did the patch blindly, but I think you get >> the idea..) > Sheesh. Just finishing up holiday email backlog and Linus already has a > fix. :) > > This looks like it should fix the issue, and does build for me. > > Assuming it works for Krzysztof, So something else may be at play. Even with Linus' patch I reproduced a similar hang here. Still chasing it down, but it looks like a seqlock deadlock where we're calling read while holding the lock. thanks -john