From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Wang Nan <wangnan0@huawei.com>,
mingo@redhat.com, linux-kernel@vger.kernel.org,
He Kuang <hekuang@huawei.com>,
Alexei Starovoitov <ast@kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Brendan Gregg <brendan.d.gregg@gmail.com>,
Jiri Olsa <jolsa@kernel.org>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Namhyung Kim <namhyung@kernel.org>, Zefan Li <lizefan@huawei.com>,
pi3orama@163.com
Subject: Re: [PATCH 2/5] perf core: Set event's default overflow_handler
Date: Wed, 23 Mar 2016 20:13:59 +0100 [thread overview]
Message-ID: <20160323191359.GL6356@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160323181348.GA2149@arm.com>
On Wed, Mar 23, 2016 at 06:13:49PM +0000, Will Deacon wrote:
> > Will, why does it matter what the overflow handler is for this stuff?
>
> Because ptrace registers an overflow handler for raising a SIGTRAP and
> ptrace users (e.g. GDB) expect to handle the single-stepping themselves.
> Perf, on the other hand, will livelock if the kernel doesn't do the
> stepping.
Ah makes sense.
> FWIW, I hate this whole thing. The only users of the perf side just seem
> to be people running whacky test cases and then pointing out the places
> where we're not identical to x86 :(
Yeah, its not my favourite part either. The whole breakpoint thing
doesn't quite behave like a regular PMU so its all a bit 'special'.
next prev parent reply other threads:[~2016-03-23 19:14 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-14 9:59 [PATCH 0/5] perf core: Support overwrite ring buffer Wang Nan
2016-03-14 9:59 ` [PATCH 1/5] perf core: Introduce new ioctl options to pause and resume " Wang Nan
2016-03-23 9:16 ` Peter Zijlstra
2016-03-23 9:33 ` Wangnan (F)
2016-03-23 9:52 ` Peter Zijlstra
2016-03-23 12:43 ` Vince Weaver
2016-10-21 7:06 ` Michael Kerrisk (man-pages)
2016-10-21 7:13 ` Wangnan (F)
2016-10-21 8:55 ` Michael Kerrisk (man-pages)
2016-03-14 9:59 ` [PATCH 2/5] perf core: Set event's default overflow_handler Wang Nan
2016-03-23 17:50 ` Peter Zijlstra
2016-03-23 18:13 ` Will Deacon
2016-03-23 19:13 ` Peter Zijlstra [this message]
2016-03-23 19:29 ` Peter Zijlstra
2016-03-24 9:58 ` Will Deacon
2016-03-24 10:42 ` Peter Zijlstra
2016-03-14 9:59 ` [PATCH 3/5] perf core: Prepare writing into ring buffer from end Wang Nan
2016-03-23 9:50 ` Peter Zijlstra
2016-03-23 10:08 ` Wangnan (F)
2016-03-23 19:25 ` Alexei Starovoitov
2016-03-24 3:48 ` Wangnan (F)
2016-03-24 17:29 ` Alexei Starovoitov
2016-03-25 12:26 ` Wangnan (F)
2016-03-25 12:36 ` Wangnan (F)
2016-03-25 14:14 ` Wangnan (F)
2016-03-27 15:20 ` Peter Zijlstra
2016-03-27 15:30 ` pi3orama
2016-03-28 1:07 ` Wangnan (F)
2016-03-28 1:58 ` Wangnan (F)
2016-03-28 2:58 ` Wangnan (F)
2016-03-14 9:59 ` [PATCH 4/5] perf core: Add backward attribute to perf event Wang Nan
2016-03-14 9:59 ` [PATCH 5/5] perf core: Reduce perf event output overhead by new overflow handler Wang Nan
2016-03-23 10:02 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2016-01-25 8:33 [PATCH 0/5] perf core: Read from overwrite ring buffer Wang Nan
2016-01-25 8:33 ` [PATCH 2/5] perf core: Set event's default overflow_handler Wang Nan
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