Messages in this thread | | | Date | Wed, 8 May 2013 08:54:47 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf record: handle death by SIGTERM |
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* David Ahern <dsahern@gmail.com> wrote:
> On 5/7/13 12:29 AM, Ingo Molnar wrote: > > > >* Stephane Eranian <eranian@google.com> wrote: > > > >>This is a good fix. I have run into this infinite loop in perf report > >>many times. > > > >Hm, perf record should really not assume much about the perf.data and > >should avoid infinite loops ... > > > >So while making perf.data more consistent on SIGTERM is a nice fix, perf > >report should be fixed as well to detect loops and such. > > > >Thanks, > > > > Ingo > > > > This seems to do the trick: > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > index 326068a..e82646f 100644 > --- a/tools/perf/util/header.c > +++ b/tools/perf/util/header.c > @@ -2802,6 +2802,17 @@ int perf_session__read_header(struct > perf_session *session, int fd) > if (perf_file_header__read(&f_header, header, fd) < 0) > return -EINVAL; > > + /* > + * sanity check that perf.data was written cleanly: data size > + * is initialized to 0 and updated only if the on_exit function > + * is run. If data size is still 0 then the file cannot be > + * processed. > + */ > + if (f_header.data.size == 0) { > + pr_err("data size is 0. Was record properly terminated?\n"); > + return -1; > + }
Hm, this detects the condition - but where does the looping come from?
Can it happen with a perf.data that 'seems' clean but is corrupted (because not fully written, buggy kernel just crashed, etc.).
In essence it would be _very_ nice if someone reproduced the looping and checked what to do to fix the looping itself. Or does the above data.size == 0 check fully fix the looping under every possible state of a perf.data?
Thanks,
Ingo
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