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From: Vince Weaver <vincent.weaver@maine.edu>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Stephane Eranian <eranian@google.com>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: perf: perf_fuzzer lockup in perf_cgroup_attach
Date: Thu, 15 Sep 2016 08:41:52 -0400 (EDT)	[thread overview]
Message-ID: <alpine.DEB.2.20.1609150839130.13216@macbook-air> (raw)
In-Reply-To: <20160915071500.GM5008@twins.programming.kicks-ass.net>

On Thu, 15 Sep 2016, Peter Zijlstra wrote:

> On Wed, Sep 14, 2016 at 10:43:29PM -0400, Vince Weaver wrote:
> > 
> > so the skylake that was fuzzing finally is mostly locked up.
> > 
> > Really hard to tell what's going, especially as KASLR made looking up the 
> > addresses a big pain.
> > 
> > The best I can tell things are getting wedged somehow in 
> > perf_cgroup_switch() while interrupts are disabled.  Interrupts are never 
> > getting re-enabled, causing the RCU and NMI watchdogs to trigger (and more 
> > alarming things like the SATA bus resetting).
> 
> How do you go about using cgroups? Do you set them up yourself, does the
> fuzzer do so?

that's an interesting thing, I don't think the fuzzer actually sets up any 
cgroups.  It will try creating events with PERF_FLAG_PID_CGROUP but it 
will just use a random number as the cgroup fd.  

I know at one time I meant to do more interesting things with cgroups
but if I recall it wasn't really possible without running as root and I 
usually don't fuzz as root.

Vince

      reply	other threads:[~2016-09-15 12:41 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-15  2:43 perf: perf_fuzzer lockup in perf_cgroup_attach Vince Weaver
2016-09-15  5:35 ` Stephane Eranian
2016-09-15  7:24   ` Peter Zijlstra
2016-09-15 12:10     ` Josh Poimboeuf
2016-09-16 14:48       ` [PATCH] scripts: add script for translating stack dump function offsets Josh Poimboeuf
2016-09-16 18:12         ` Linus Torvalds
2016-09-16 19:17           ` Josh Poimboeuf
2016-09-16 19:26             ` Linus Torvalds
2016-09-16 21:26               ` [PATCH v2] " Josh Poimboeuf
2016-09-17  0:09                 ` Linus Torvalds
2016-09-17  0:42                   ` Josh Poimboeuf
2016-09-17  1:59                     ` Linus Torvalds
2016-09-17  2:31                       ` Linus Torvalds
2016-09-17 18:45                       ` Josh Poimboeuf
2016-09-19 15:52                       ` [PATCH v3] scripts: add script for translating stack dump function Josh Poimboeuf
2016-09-19 18:56                         ` Linus Torvalds
2016-09-19 19:15                           ` Linus Torvalds
2016-09-19 19:28                             ` Josh Poimboeuf
2016-09-19 20:00                             ` Rabin Vincent
2016-09-19 20:24                               ` Linus Torvalds
2016-09-19 20:56                                 ` Josh Poimboeuf
2016-09-19 21:02                                   ` Linus Torvalds
2016-09-19 21:07                                     ` Josh Poimboeuf
2016-09-17  1:25                 ` [PATCH v2] scripts: add script for translating stack dump function offsets Peter Zijlstra
2016-09-17  8:15                 ` Rabin Vincent
2016-09-17 18:48                   ` Josh Poimboeuf
2016-09-17  9:11             ` [PATCH] " Vegard Nossum
2016-09-17 18:54               ` Josh Poimboeuf
2016-09-15 12:47   ` perf: perf_fuzzer lockup in perf_cgroup_attach Vince Weaver
2016-09-15  7:15 ` Peter Zijlstra
2016-09-15 12:41   ` Vince Weaver [this message]

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