Re: [PATCHv5] perf tools: enable close-on-exec flag on perf file descriptor

[Jiri Olsa <jolsa@redhat.com>]

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