Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Alexander Shishkin <alexander.shishkin@linux.intel.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Mark Rutland <mark.rutland@arm.com>
Cc:     Arnaldo Carvalho de Melo <acme@redhat.com>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        jolsa@redhat.com, dvyukov@google.com, namhyung@kernel.org,
        xiexiuqi@huawei.com,
        syzbot+a24c397a29ad22d86c98@syzkaller.appspotmail.com,
        alexander.shishkin@linux.intel.com
Subject: Re: [PATCH] perf: Fix race between close() and fork()
In-Reply-To: <20190625104320.GZ3463@hirez.programming.kicks-ass.net>
References: <278ac311-d8f3-2832-5fa1-522471c8c31c@huawei.com> <20190228140109.64238-1-alexander.shishkin@linux.intel.com> <20190308155429.GB10860@lakrids.cambridge.arm.com> <20190624121902.GE3436@hirez.programming.kicks-ass.net> <20190625084904.GY3463@hirez.programming.kicks-ass.net> <20190625104320.GZ3463@hirez.programming.kicks-ass.net>
Date:   Tue, 25 Jun 2019 15:20:33 +0300
Message-ID: <87h88dvotq.fsf@ashishki-desk.ger.corp.intel.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Peter Zijlstra <peterz@infradead.org> writes:

> Solve it by using the fact that detached events still have a reference
> count on their (previous) context. With this perf_event_free_task()
> can detect when events have escaped and wait for their destruction.
>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Fixes: 82d94856fa22 ("perf/core: Fix lock inversion between perf,trace,cpuhp")
> Reported-by: syzbot+a24c397a29ad22d86c98@syzkaller.appspotmail.com
> Debugged-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

Regards,
--
Alex