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Message-ID: <20140602192320.GD7861@krava.brq.redhat.com>
Date: Mon, 2 Jun 2014 21:23:20 +0200
From: Jiri Olsa <jolsa@...hat.com>
To: Yann Droneaud <ydroneaud@...eya.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>
Subject: Re: [PATCHv5] perf tools: enable close-on-exec flag on perf file
descriptor
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 ;-)
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
>
> 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
>
> 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
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
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.
> + } 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
thanks,
jirka
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