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From: Yabin Cui <yabinc@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>
Cc: linux-kernel@vger.kernel.org, Yabin Cui <yabinc@google.com>
Subject: Re: [PATCH] perf/ring_buffer: Fix exposing a temporarily decreased data_head.
Date: Thu, 16 May 2019 11:37:47 -0700	[thread overview]
Message-ID: <20190516183747.166545-1-yabinc@google.com> (raw)
In-Reply-To: <20190515104824.GD2623@hirez.programming.kicks-ass.net>

>Indeed, good catch! Have you observed this, or is this patch due to code
inspection?

I observed this. I was using perf_event_open instead of linux tools perf
to monitor a process continuously forking new processes, generating a lot
of mmap records. And a sample record happens while generating a mmap record.

For missing barriers, I thought local_xxx provided implied barriers. But
I found atomic_ops.txt said not. Thanks for reminding! I will add them in
path v2.

I also think it's a good idea to use READ_ONCE/WRITE_ONCE for rb->nest. Will
use it in patch v2.


  reply	other threads:[~2019-05-16 18:38 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-15  0:30 Yabin Cui
2019-05-15  6:51 ` Alexander Shishkin
2019-05-15  9:43   ` Peter Zijlstra
2019-05-15 10:04     ` Alexander Shishkin
2019-05-15 10:51       ` Peter Zijlstra
2019-05-15 10:48 ` Peter Zijlstra
2019-05-16 18:37   ` Yabin Cui [this message]
2019-05-16 18:40 ` [PATCH v2] " Yabin Cui
2019-05-17  8:47   ` Peter Zijlstra
2019-05-17 17:59     ` [PATCH] " Yabin Cui

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