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Date: Wed, 13 Nov 2013 18:36:55 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: John Stultz <john.stultz@linaro.org>, LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Vivek Goyal <vgoyal@redhat.com>,
        Fengguang Wu <fengguang.wu@intel.com>
Subject: Re: [PATCH] block: Employ u64_stats_init()
Message-ID: <20131113173655.GB10482@gmail.com>
References: <1384314134-6895-1-git-send-email-john.stultz@linaro.org>
 <5283A10E.2090304@kernel.dk>
 <20131113173521.GA10482@gmail.com>
 <5283B87E.2070703@kernel.dk>
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* Jens Axboe <axboe@kernel.dk> wrote:

> On 11/13/2013 10:35 AM, Ingo Molnar wrote:
> > 
> > * Jens Axboe <axboe@kernel.dk> wrote:
> > 
> >> On 11/12/2013 08:42 PM, John Stultz wrote:
> >>> From: Peter Zijlstra <peterz@infradead.org>
> >>>
> >>> Now that seqcounts are lockdep enabled objects, we need to properly
> >>> initialize them.
> >>>
> >>> Without this patch, Fengguang was seeing:
> >>> [    4.127282] INFO: trying to register non-static key.
> >>> [    4.128027] the code is fine but needs lockdep annotation.
> >>> [    4.128027] turning off the locking correctness validator.
> >>> [    4.128027] CPU: 0 PID: 96 Comm: kworker/u4:1 Not tainted 3.12.0-next-20131108-10601-gbad570d #2
> >>> [    4.128027] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> >>> [    4.128027] Workqueue: events_unbound async_run_entry_fn
> >>> [    4.128027]  7908e744 00000000 78019968 79dc7cf2 7a80e0a8 780199a0 7908953e 7a1b7f4d
> >>> [    4.128027]  7a1b7fa7 7a1b7f7d 7f368608 00000000 00000011 44374011 0000a805 7f368110
> >>> [    4.128027]  7f368110 85bf2a70 00000000 780199cc 7908a1c5 00000000 00000001 00000000
> >>> [    4.128027] Call Trace:
> >>> [    4.128027]  [<7908e744>] ? console_unlock+0x353/0x380
> >>> [    4.128027]  [<79dc7cf2>] dump_stack+0x48/0x60
> >>> [    4.128027]  [<7908953e>] __lock_acquire.isra.26+0x7e3/0xceb
> >>> [    4.128027]  [<7908a1c5>] lock_acquire+0x71/0x9a
> >>> [    4.128027]  [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
> >>> [    4.128027]  [<7940658b>] throtl_update_dispatch_stats+0x7c/0x153
> >>> [    4.128027]  [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
> >>> [    4.128027]  [<794079aa>] blk_throtl_bio+0x1c3/0x485
> >>> ...
> >>>
> >>> Cc: Vivek Goyal <vgoyal@redhat.com>
> >>> Cc: Jens Axboe <axboe@kernel.dk>
> >>> Cc: Fengguang Wu <fengguang.wu@intel.com>
> >>> Cc: Ingo Molnar <mingo@kernel.org>
> >>> Reported-by: Fengguang Wu <fengguang.wu@intel.com>
> >>> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> >>> [jstultz: Folded in another fix from the mailing list as well as a fix
> >>> to that fix. Tweaked commit message.]
> >>> Signed-off-by: John Stultz <john.stultz@linaro.org>
> >>
> >> Thanks for fixing this up, John/Peter. I'll get it queued up.
> > 
> > Note that I've already applied it to the locking tree earlier today and
> > sent it to Linus, didn't want to expose upstream to known false positives.
> 
> OK, that works for me, thanks!

Also, if it breaks I'll take full responsibility for messing up! :-)

Thanks,

	Ingo