From: Peter Zijlstra <peterz@infradead.org>
To: "Wangnan (F)" <wangnan0@huawei.com>
Cc: xiakaixu <xiakaixu@huawei.com>,
Alexei Starovoitov <ast@plumgrid.com>,
davem@davemloft.net, acme@kernel.org, mingo@redhat.com,
masami.hiramatsu.pt@hitachi.com, jolsa@kernel.org,
daniel@iogearbox.net, linux-kernel@vger.kernel.org,
pi3orama@163.com, hekuang@huawei.com, netdev@vger.kernel.org
Subject: Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling
Date: Wed, 21 Oct 2015 14:17:13 +0200 [thread overview]
Message-ID: <20151021121713.GC3604@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <56277BCE.6030400@huawei.com>
On Wed, Oct 21, 2015 at 07:49:34PM +0800, Wangnan (F) wrote:
> If our task is sampling cycle events during a function is running,
> and if two cores start that function overlap:
>
> Time: ...................A
> Core 0: sys_write----\
> \
> \
> Core 1: sys_write%return
> Core 2: ................sys_write
>
> Then without counter at time A it is highly possible that
> BPF program on core 1 and core 2 get conflict with each other.
> The final result is we make some of those events be turned on
> and others turned off. Using atomic counter can avoid this
> problem.
But but, how and why can an eBPF program access a !local event? I
thought we had hard restrictions on that.
next prev parent reply other threads:[~2015-10-21 12:17 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-20 7:22 [PATCH V5 0/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling Kaixu Xia
2015-10-20 7:22 ` [PATCH V5 1/1] " Kaixu Xia
2015-10-20 22:53 ` Alexei Starovoitov
2015-10-21 9:12 ` Peter Zijlstra
2015-10-21 10:31 ` xiakaixu
2015-10-21 11:33 ` Peter Zijlstra
2015-10-21 11:49 ` Wangnan (F)
2015-10-21 12:17 ` Peter Zijlstra [this message]
2015-10-21 13:42 ` Wangnan (F)
2015-10-21 13:49 ` Peter Zijlstra
2015-10-21 14:01 ` pi3orama
2015-10-21 14:09 ` Peter Zijlstra
2015-10-21 15:06 ` pi3orama
2015-10-21 16:57 ` Peter Zijlstra
2015-10-21 21:19 ` Alexei Starovoitov
2015-10-22 9:06 ` Peter Zijlstra
2015-10-22 10:28 ` Wangnan (F)
2015-10-23 12:52 ` Peter Zijlstra
2015-10-23 15:12 ` Peter Zijlstra
2015-10-27 6:43 ` xiakaixu
2015-10-22 2:46 ` Wangnan (F)
2015-10-22 7:39 ` Ingo Molnar
2015-10-22 7:51 ` Wangnan (F)
2015-10-22 9:24 ` Peter Zijlstra
2015-10-22 1:56 ` Wangnan (F)
2015-10-22 3:09 ` Alexei Starovoitov
2015-10-22 3:12 ` Wangnan (F)
2015-10-22 3:26 ` Alexei Starovoitov
2015-10-22 9:49 ` Peter Zijlstra
2015-10-21 11:34 ` Wangnan (F)
2015-10-21 11:56 ` Peter Zijlstra
2015-10-21 12:03 ` Wangnan (F)
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