Messages in this thread | | | Date | Sat, 12 Aug 2023 09:45:52 +0800 | Subject | Re: [PATCH] tracing: Fix race when concurrently splice_read trace_pipe | From | Zheng Yejian <> |
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On 2023/8/12 03:25, Steven Rostedt wrote: > On Thu, 10 Aug 2023 20:39:05 +0800 > Zheng Yejian <zhengyejian1@huawei.com> wrote: > >> When concurrently splice_read file trace_pipe and per_cpu/cpu*/trace_pipe, >> there are more data being read out than expected.
Sorry, I didn't make clear here. It not just read more but also lost some data. My case is that, for example: 1) Inject 3 events into ring_buffer: event1, event2, event3; 2) Concurrently splice_read through trace_pipes; 3) Then actually read out: event1, event3, event3. No event2, but 2 event3.
> > Honestly the real fix is to prevent that use case. We should probably have > access to trace_pipe lock all the per_cpu trace_pipes too.
Yes, we could do that, but would it seem not that effective? because per_cpu trace_pipe only read its own ring_buffer and not race with ring_buffers in other cpus.
> > -- Steve >
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