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Date: Tue, 03 Jun 2014 10:57:15 +0200
From: Yann Droneaud <ydroneaud@...eya.com>
To: Jiri Olsa <jolsa@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Ingo Molnar <mingo@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Andi Kleen <ak@...ux.intel.com>,
David Ahern <dsahern@...il.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Mike Galbraith <efault@....de>,
Stephane Eranian <eranian@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Michael Ellerman <michael@...erman.id.au>,
Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
AdrianHunter <adrian.hunter@...el.com>, ydroneaud@...eya.com
Subject: Re: [PATCHv5] perf tools: enable close-on-exec flag on perf file
descriptor
Le lundi 02 juin 2014 à 21:23 +0200, Jiri Olsa a écrit :
> On Mon, Jun 02, 2014 at 12:56:34PM +0200, Yann Droneaud wrote:
>
> SNIP
>
> >
> > Hi,
> >
> > Quite the same patch from v4. I'm interested in some
> > feedback so that I could improve the patch if needed.
> >
> > Regards.
> >
> > Changes from v4 [1]:
> > - rebase on next-20140530 and update commit message.
>
> hi,
> I wasn't following on this one before.. so please shut me up
> if my comments were already discussed ;-)
>
You had a chance to review it before :)
See http://lkml.kernel.org/r/20140106142220.GB1183@krava.brq.redhat.com
> SNIP
>
> > index d7176830b9b2..bb4afc9fae54 100644
> > --- a/tools/perf/builtin-sched.c
> > +++ b/tools/perf/builtin-sched.c
> > @@ -10,6 +10,7 @@
> > #include "util/header.h"
> > #include "util/session.h"
> > #include "util/tool.h"
> > +#include "util/cloexec.h"
> >
> > #include "util/parse-options.h"
> > #include "util/trace-event.h"
> > @@ -434,7 +435,8 @@ static int self_open_counters(void)
> > attr.type = PERF_TYPE_SOFTWARE;
> > attr.config = PERF_COUNT_SW_TASK_CLOCK;
> >
> > - fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
> > + fd = sys_perf_event_open(&attr, 0, -1, -1,
> > + perf_event_open_cloexec_flag());
> >
> > if (fd < 0)
> > pr_err("Error: sys_perf_event_open() syscall returned "
> > diff --git a/tools/perf/tests/bp_signal.c b/tools/perf/tests/bp_signal.c
> > index aba095489193..fdc0d3e185f9 100644
> > --- a/tools/perf/tests/bp_signal.c
> > +++ b/tools/perf/tests/bp_signal.c
> > @@ -25,6 +25,7 @@
> > #include "tests.h"
> > #include "debug.h"
> > #include "perf.h"
> > +#include "../util/cloexec.h"
>
> #include "cloexec.h" should be enough
>
OK
> >
> > static int fd1;
> > static int fd2;
> > @@ -78,7 +79,8 @@ static int bp_event(void *fn, int setup_signal)
> > pe.exclude_kernel = 1;
> > pe.exclude_hv = 1;
> >
> > - fd = sys_perf_event_open(&pe, 0, -1, -1, 0);
> > + fd = sys_perf_event_open(&pe, 0, -1, -1,
> > + perf_event_open_cloexec_flag());
> > if (fd < 0) {
> > pr_debug("failed opening event %llx\n", pe.config);
> > return TEST_FAIL;
> > diff --git a/tools/perf/tests/bp_signal_overflow.c b/tools/perf/tests/bp_signal_overflow.c
> > index 44ac82179708..b0b17415f18c 100644
> > --- a/tools/perf/tests/bp_signal_overflow.c
> > +++ b/tools/perf/tests/bp_signal_overflow.c
> > @@ -24,6 +24,7 @@
> > #include "tests.h"
> > #include "debug.h"
> > #include "perf.h"
> > +#include "../util/cloexec.h"
>
> ditto
>
OK
> >
> > static int overflows;
> >
> > @@ -91,7 +92,8 @@ int test__bp_signal_overflow(void)
> > pe.exclude_kernel = 1;
> > pe.exclude_hv = 1;
> >
> > - fd = sys_perf_event_open(&pe, 0, -1, -1, 0);
> > + fd = sys_perf_event_open(&pe, 0, -1, -1,
> > + perf_event_open_cloexec_flag());
> > if (fd < 0) {
> > pr_debug("failed opening event %llx\n", pe.config);
> > return TEST_FAIL;
> > diff --git a/tools/perf/tests/rdpmc.c b/tools/perf/tests/rdpmc.c
> > index e59143fd9e71..8432bfcffed6 100644
> > --- a/tools/perf/tests/rdpmc.c
> > +++ b/tools/perf/tests/rdpmc.c
> > @@ -6,6 +6,7 @@
> > #include "perf.h"
> > #include "debug.h"
> > #include "tests.h"
> > +#include "../util/cloexec.h"
>
> ditto
>
OK
> SNIP
>
> > +
> > +static int perf_flag_probe(void)
> > +{
> > + /* use 'safest' configuration as used in perf_evsel__fallback() */
> > + struct perf_event_attr attr = {
> > + .type = PERF_COUNT_SW_CPU_CLOCK,
> > + .config = PERF_COUNT_SW_CPU_CLOCK,
> > + };
> > + int fd;
> > + int err;
> > +
> > + /* check cloexec flag */
> > + fd = sys_perf_event_open(&attr, 0, -1, -1,
> > + PERF_FLAG_FD_CLOEXEC);
> > + if (fd >= 0) {
> > + close(fd);
> > + return 1;
> > + }
> > +
> > + if (errno != EINVAL) {
> > + err = errno;
> > + pr_warning("sys_perf_event_open() syscall returned "
> > + "%d (%d: %s)\n", fd, err, strerror(err));
> > + }
> > +
> > + /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
> > + fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
> > + if (fd >= 0) {
> > + close(fd);
> > + return 0;
> > + }
> > +
> > + err = errno;
> > + die("sys_perf_event_open() syscall returned "
> > + "%d (%d: %s)\n", fd, err, strerror(err));
>
> I think we have a strategy of not using die in new code..
> please just use WARN_ONCE.. and let the code fail in the
> standard way
>
OK
> SNIP
>
> >
> > #define FD(e, x, y) (*(int *)xyarray__entry(e->fd, x, y))
> > @@ -988,7 +989,7 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
> > struct thread_map *threads)
> > {
> > int cpu, thread;
> > - unsigned long flags = 0;
> > + unsigned long flags = PERF_FLAG_FD_CLOEXEC;
> > int pid = -1, err;
> > enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;
> >
> > @@ -997,11 +998,13 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
> > return -ENOMEM;
> >
> > if (evsel->cgrp) {
> > - flags = PERF_FLAG_PID_CGROUP;
> > + flags |= PERF_FLAG_PID_CGROUP;
> > pid = evsel->cgrp->fd;
> > }
> >
> > fallback_missing_features:
> > + if (perf_missing_features.cloexec)
> > + flags &= ~(unsigned long)PERF_FLAG_FD_CLOEXEC;
> > if (perf_missing_features.mmap2)
> > evsel->attr.mmap2 = 0;
> > if (perf_missing_features.exclude_guest)
> > @@ -1070,7 +1073,10 @@ try_fallback:
> > if (err != -EINVAL || cpu > 0 || thread > 0)
> > goto out_close;
> >
> > - if (!perf_missing_features.mmap2 && evsel->attr.mmap2) {
> > + if (!perf_missing_features.cloexec && (flags & PERF_FLAG_FD_CLOEXEC)) {
> > + perf_missing_features.cloexec = true;
> > + goto fallback_missing_features;
>
> I think it does not fit in here, because we check latest perf_event_attr
> bits and removing one after another, to see if miracle happens.
> (also looks like we miss exclude_callchain_(kernel|user) bits)
>
> Wouldn't it be better just to use perf_event_open_cloexec_flag() function
> as you did in the rest of the code? I think we dont need 2 detection codes
> for this.
>
I was asked by ACME to use here the missing feature detection pattern
and to treat the flag just as a new feature like perf_event_attr new
attributes.
See http://lkml.kernel.org/r/20140106144347.GA13500@ghostprotocols.net
http://lkml.kernel.org/r/20140106211444.GD2810@ghostprotocols.net
> > + } else if (!perf_missing_features.mmap2 && evsel->attr.mmap2) {
> > perf_missing_features.mmap2 = true;
> > goto fallback_missing_features;
> > } else if (!perf_missing_features.exclude_guest &&
> > diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
> > index 049e0a09ccd3..9a8d622809f6 100644
> > --- a/tools/perf/util/record.c
> > +++ b/tools/perf/util/record.c
> > @@ -4,6 +4,7 @@
> > #include "parse-events.h"
> > #include <api/fs/fs.h>
> > #include "util.h"
> > +#include "cloexec.h"
> >
> > typedef void (*setup_probe_fn_t)(struct perf_evsel *evsel);
> >
> > @@ -11,6 +12,7 @@ static int perf_do_probe_api(setup_probe_fn_t fn, int cpu, const char *str)
> > {
> > struct perf_evlist *evlist;
> > struct perf_evsel *evsel;
> > + unsigned long flags = perf_event_open_cloexec_flag();
> > int err = -EAGAIN, fd;
> >
> > evlist = perf_evlist__new();
> > @@ -22,14 +24,14 @@ static int perf_do_probe_api(setup_probe_fn_t fn, int cpu, const char *str)
> >
> > evsel = perf_evlist__first(evlist);
> >
> > - fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, 0);
> > + fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, flags);
> > if (fd < 0)
> > goto out_delete;
> > close(fd);
> >
> > fn(evsel);
> >
> > - fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, 0);
> > + fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, flags);
> > if (fd < 0) {
> > if (errno == EINVAL)
> > err = -EINVAL;
> > @@ -203,7 +205,8 @@ bool perf_evlist__can_select_event(struct perf_evlist *evlist, const char *str)
> > cpu = evlist->cpus->map[0];
> > }
>
> hum... no one calls this exported function ^^^ :-) I wonder why it's there.. cool
>
Nice catch. This function was introduced by commit
c09ec622629eeb4b7877646a42852e7156363425 ('perf evlist: Add
can_select_event() method') by Adrian Hunter <adrian.hunter@...el.com>
and it seems it was never used by perf tools.
Is it available to some outside tree perf tools ?
Thanks for the review.
Regards
--
Yann Droneaud
OPTEYA
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