From: Ingo Molnar <mingo@kernel.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Vince Weaver <vincent.weaver@maine.edu>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Stephane Eranian <eranian@gmail.com>
Subject: Re: perf: aux area related crash and warnings
Date: Mon, 15 Jun 2015 22:24:36 +0200 [thread overview]
Message-ID: <20150615202435.GB12450@gmail.com> (raw)
In-Reply-To: <87egld2l2o.fsf@ashishki-desk.ger.corp.intel.com>
* Alexander Shishkin <alexander.shishkin@linux.intel.com> wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
> > Alex, any clue?
>
> Let me look into it. Definitely haven't seen anything like that in my
> tests.
That's natural: Vince is running randomize fuzzing tests, so you should look out
for boundary conditions and 'nonsensical' values that won't normally trigger in
functional testing.
In fact Vince is using 'directed fuzzing': i.e. the fuzzer is aware of the general
perf ABI structure and will try to generate partially valid, partially randomized
requests, to be able to test 'leaf' functionality of the perf ABI as well, which
would otherwise need astronomical odds to occur in a pure fuzzing test.
These crashes started popping up when Vince added 'AUX area awareness' to the
fuzzer.
> >> [36299.068111] [<ffffffff810c2acf>] do_raw_spin_lock+0x13f/0x180
> >> [36299.074897] [<ffffffff816de6e9>] _raw_spin_lock+0x39/0x40
> >> [36299.081276] [<ffffffff8117a039>] ? free_pcppages_bulk+0x39/0x620
> >> [36299.088340] [<ffffffff8117a039>] free_pcppages_bulk+0x39/0x620
> >> [36299.095182] [<ffffffff81177e14>] ? free_pages_prepare+0x3a4/0x550
> >> [36299.102291] [<ffffffff811c9936>] ? kfree_debugcheck+0x16/0x40
> >> [36299.108987] [<ffffffff8117a938>] free_hot_cold_page+0x178/0x1a0
> >> [36299.115850] [<ffffffff8117aa47>] __free_pages+0x37/0x50
> >> [36299.121991] [<ffffffff8116ae0a>] rb_free_aux+0xba/0xf0
>
> This one goes to free aux pages from nmi context, looks like aux buffer was
> unmapped while the event was running, so here it dropped the last reference.
Yeah, that in itself is an absolute no-no - so I guess refcounting went wrong
somewhere? (assuming it exists properly).
Thanks,
Ingo
next prev parent reply other threads:[~2015-06-15 20:24 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-12 3:15 perf: aux area related crash and warnings Vince Weaver
2015-06-12 18:42 ` Vince Weaver
2015-06-15 12:20 ` Peter Zijlstra
2015-06-15 12:49 ` Alexander Shishkin
2015-06-15 20:24 ` Ingo Molnar [this message]
2015-06-16 11:37 ` Alexander Shishkin
2015-06-18 9:09 ` Ingo Molnar
2015-06-18 9:35 ` Alexander Shishkin
2015-06-18 10:24 ` Peter Zijlstra
2015-06-18 16:30 ` Paul E. McKenney
2015-06-18 10:32 ` Peter Zijlstra
2015-06-18 13:11 ` Alexander Shishkin
2015-06-19 14:21 ` Vince Weaver
2015-07-06 15:34 ` [tip:perf/urgent] perf: Fix AUX buffer refcounting tip-bot for Peter Zijlstra
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