Messages in this thread | | | Subject | Re: [PATCH] perf tools: enable close-on-exec flag on perf file descriptor | From | Yann Droneaud <> | Date | Mon, 06 Jan 2014 22:01:35 +0100 |
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Hi,
Le lundi 06 janvier 2014 à 11:43 -0300, Arnaldo Carvalho de Melo a écrit : > Em Mon, Jan 06, 2014 at 12:24:36PM +0100, Peter Zijlstra escreveu:
> > acme, ACK? I was thinking I'd keep these two patches together so the > > entire things lands in tip in one go? > > Nope, it should notice the EINVAL, drop the flag that doesn't work on > older kernels, retry, so that new tools continue to work on older > kernels, with yet another fallback. >
But it may be difficult to distinguish the 'origin' of EINVAL: is it from FD_CLOEXEC flag or from an unsupported parameter in the attributes.
> Please take a look at __perf_evsel__open(), probably it will be best to > add a flag to perf_missing_features, like the one we have for the > perf_event_attr.mmap2 flag, so that we fail just once, etc. >
Unfortunately perf_event_open() is called in multiple places, not only in __perf_evsel__open(). So a more generic solution should be designed.
Is something like the function proposed in message <1389022310.13828.9.camel@localhost.localdomain> [1] ok to be added to its own module:
static int cloexec = PERF_FLAG_FD_CLOEXEC;
int perf_flag_fd_cloexec(void) { static int probed;
if (!probed) { struct perf_event_attr attr = { 0 }; int fd = perf_event_open(&attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC); probed = 1; if (fd >= 0) close(fd); else cloexec = 0; }
return cloexec; }
This function should be used to build the flag passed to perf_event_open().
Regards.
[1] http://lkml.kernel.org/r/1389022310.13828.9.camel@localhost.localdomain
-- Yann Droneaud OPTEYA
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