linux-kernel - Re: [BUG REPORT]: ARM64: perf: System hung in perf test

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Message-ID: <20151221140104.GQ23092@arm.com>
Date:	Mon, 21 Dec 2015 14:01:04 +0000
From:	Will Deacon <will.deacon@....com>
To:	"Wangnan (F)" <wangnan0@...wei.com>
Cc:	guohanjun@...wei.com, Jiri Olsa <jolsa@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	pi3orama <pi3orama@....com>,
	xiakaixu 00238161 <xiakaixu@...wei.com>
Subject: Re: [BUG REPORT]: ARM64: perf: System hung in perf test

On Mon, Dec 21, 2015 at 08:56:03PM +0800, Wangnan (F) wrote:
> System hung can be reproduced on qemu and real hardware using:
> 
>  # perf test -v signal
> 
> If qemu is started with '-smp 1', system hung. In real hardware and in
> qemu with smp > 1, the result is:

That sounds like a qemu issue...

>  # /perf test -v signal
>  17: Test breakpoint overflow signal handler                  :
>  --- start ---
>  test child forked, pid 792
>  count1 11, count2 11, overflow 11
>  failed: RF EFLAG recursion issue detected
>  failed: wrong overflow hit
>  failed: wrong count for bp2
>  test child finished with -1
>  ---- end ----
>  Test breakpoint overflow signal handler: FAILED!

... and this sounds like the perf tool expecting to single-step over
signal handlers, whereas (on arm64) we deliberately single-step into
them, so you can run into a loop for this case.

Will
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