2019-10-20 17:53:22

by Andi Kleen

Subject: [PATCH v2 1/9] perf evsel: Always preserve errno while cleaning up perf_event_open failures

From: Andi Kleen <[email protected]>

In some cases when perf_event_open fails, it may do some closes to clean
up. In special cases these closes can fail too, which overwrites the
errno of the perf_event_open, which is then incorrectly reported.

Save/restore errno around closes.

Signed-off-by: Andi Kleen <[email protected]>
---
tools/perf/util/evsel.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index abc7fda4a0fe..d831038b55f2 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1574,7 +1574,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
{
int cpu, thread, nthreads;
unsigned long flags = PERF_FLAG_FD_CLOEXEC;
- int pid = -1, err;
+ int pid = -1, err, old_errno;
enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;

if ((perf_missing_features.write_backward && evsel->core.attr.write_backward) ||
@@ -1727,8 +1727,8 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
*/
if (err == -EMFILE && set_rlimit < INCREASED_MAX) {
struct rlimit l;
- int old_errno = errno;

+ old_errno = errno;
if (getrlimit(RLIMIT_NOFILE, &l) == 0) {
if (set_rlimit == NO_CHANGE)
l.rlim_cur = l.rlim_max;
@@ -1812,6 +1812,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
if (err)
threads->err_thread = thread;

+ old_errno = errno;
do {
while (--thread >= 0) {
close(FD(evsel, cpu, thread));
@@ -1819,6 +1820,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
}
thread = nthreads;
} while (--cpu >= 0);
+ errno = old_errno;
return err;
}

--
2.21.0

2019-10-22 08:04:25

by Jiri Olsa

Subject: Re: [PATCH v2 1/9] perf evsel: Always preserve errno while cleaning up perf_event_open failures

On Sun, Oct 20, 2019 at 10:51:54AM -0700, Andi Kleen wrote:
> From: Andi Kleen <[email protected]>
>
> In some cases when perf_event_open fails, it may do some closes to clean
> up. In special cases these closes can fail too, which overwrites the
> errno of the perf_event_open, which is then incorrectly reported.
>
> Save/restore errno around closes.
>
> Signed-off-by: Andi Kleen <[email protected]>

Acked-by: Jiri Olsa <[email protected]>

thanks,
jirka

> ---
> tools/perf/util/evsel.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index abc7fda4a0fe..d831038b55f2 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1574,7 +1574,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
> {
> int cpu, thread, nthreads;
> unsigned long flags = PERF_FLAG_FD_CLOEXEC;
> - int pid = -1, err;
> + int pid = -1, err, old_errno;
> enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;
>
> if ((perf_missing_features.write_backward && evsel->core.attr.write_backward) ||
> @@ -1727,8 +1727,8 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
> */
> if (err == -EMFILE && set_rlimit < INCREASED_MAX) {
> struct rlimit l;
> - int old_errno = errno;
>
> + old_errno = errno;
> if (getrlimit(RLIMIT_NOFILE, &l) == 0) {
> if (set_rlimit == NO_CHANGE)
> l.rlim_cur = l.rlim_max;
> @@ -1812,6 +1812,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
> if (err)
> threads->err_thread = thread;
>
> + old_errno = errno;
> do {
> while (--thread >= 0) {
> close(FD(evsel, cpu, thread));
> @@ -1819,6 +1820,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
> }
> thread = nthreads;
> } while (--cpu >= 0);
> + errno = old_errno;
> return err;
> }
>
> --
> 2.21.0
>

2019-11-12 11:22:19

by tip-bot2 for Alexey Makhalov

Subject: [tip: perf/core] perf evsel: Always preserve errno while cleaning up perf_event_open failures

The following commit has been merged into the perf/core branch of tip:

Commit-ID: 796c01a4bfb4b35ec6d1bd1cd5d520515d078b51
Gitweb: https://git.kernel.org/tip/796c01a4bfb4b35ec6d1bd1cd5d520515d078b51
Author: Andi Kleen <[email protected]>
AuthorDate: Sun, 20 Oct 2019 10:51:54 -07:00
Committer: Arnaldo Carvalho de Melo <[email protected]>
CommitterDate: Wed, 06 Nov 2019 15:43:05 -03:00

perf evsel: Always preserve errno while cleaning up perf_event_open failures

In some cases when perf_event_open fails, it may do some closes to clean
up. In special cases these closes can fail too, which overwrites the
errno of the perf_event_open, which is then incorrectly reported.

Save/restore errno around closes.

Signed-off-by: Andi Kleen <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/perf/util/evsel.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index abc7fda..d831038 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1574,7 +1574,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
{
int cpu, thread, nthreads;
unsigned long flags = PERF_FLAG_FD_CLOEXEC;
- int pid = -1, err;
+ int pid = -1, err, old_errno;
enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;

if ((perf_missing_features.write_backward && evsel->core.attr.write_backward) ||
@@ -1727,8 +1727,8 @@ try_fallback:
*/
if (err == -EMFILE && set_rlimit < INCREASED_MAX) {
struct rlimit l;
- int old_errno = errno;

+ old_errno = errno;
if (getrlimit(RLIMIT_NOFILE, &l) == 0) {
if (set_rlimit == NO_CHANGE)
l.rlim_cur = l.rlim_max;
@@ -1812,6 +1812,7 @@ out_close:
if (err)
threads->err_thread = thread;

+ old_errno = errno;
do {
while (--thread >= 0) {
close(FD(evsel, cpu, thread));
@@ -1819,6 +1820,7 @@ out_close:
}
thread = nthreads;
} while (--cpu >= 0);
+ errno = old_errno;
return err;
}