Date: Thu, 11 Jan 2018 20:01:48 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7
Message-ID: <20180111190148.GO3040@hirez.programming.kicks-ass.net>
References: <20180109132602.GA2369@hirez.programming.kicks-ass.net>
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 <20180111091353.GW6176@hirez.programming.kicks-ass.net>
 <alpine.DEB.2.21.1801111022520.21701@macbook-air>
 <20180111153845.GD6176@hirez.programming.kicks-ass.net>
 <alpine.DEB.2.21.1801111139320.22460@macbook-air>
 <alpine.DEB.2.21.1801111144450.22460@macbook-air>
 <20180111170347.GG6176@hirez.programming.kicks-ass.net>
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On Thu, Jan 11, 2018 at 01:20:10PM -0500, Vince Weaver wrote:
> On Thu, 11 Jan 2018, Vince Weaver wrote:
> 
> > on the same core2 machine I got this which didn't crash the machine (but 
> > the perf_fuzzer process is stuck)
> 
> also got this one:
> 
> Cannot open /sys/kernel/tracing/kprobe_events
> [  408.159243] watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [perf_fuzzer:22326]

Yes, I got plenty of those. Mostly they appear false positives, because
the next time the soft watchdog triggers on the same CPU the callchains
are completely unrelated. So its just 'slow' not stuck.