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perf tools: Show better error message in case we fail to open counters due to EBUSY error

PATCH In review Jiri Olsa 4 participants 8 messages Aug 1, 2014 – Aug 13, 2014 perf events

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Jiri Olsa

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#0 lore raw

PATCH 1/1 perf tools: Show better error message in case we fail to open counters due to EBUSY error

Showing better error message in case we fail to open counters due to the EBUSY error. If we detect oprofile daemon process running, we now display following message for EBUSY error:

  $ perf record ls
  Error:
  The PMU counters are busy/taken by another profiler.
  We found oprofile daemon running, please stop it and try again.

In case oprofiled was not detected the current error message stays:

  $ perf record ls
  Error:
  The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (cycles).
  /bin/dmesg may provide additional information.
  No CONFIG_PERF_EVENTS=y kernel support configured?

Also changing PERF_FLAG_FD_CLOEXEC detection code not to display error in case of EBUSY error, as it currently does:

  $ perf record ls
  Error:
  perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 16 (Device or resource busy)
  perf_event_open(..., 0) failed unexpectedly with error 16 (Device or resource busy)
  The PMU counters are busy/taken by another profiler.
  We found oprofile daemon running, please stop it and try again.
Cc Adrian Hunter <[email protected]>
Cc Arnaldo Carvalho de Melo <[email protected]>
Cc David Ahern <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc William Cohen <[email protected]>
Cc Yann Droneaud <[email protected]>
Signed-off-by Jiri Olsa <[email protected]>
---
 tools/perf/util/cloexec.c |  4 ++--
 tools/perf/util/evsel.c   |  6 ++++++
 tools/perf/util/util.c    | 36 ++++++++++++++++++++++++++++++++++++
 tools/perf/util/util.h    |  1 +
 4 files changed, 45 insertions(+), 2 deletions(-)
tools/perf/util/cloexec.c +2 -2
index c5d05ec17220..dede0c388ed4 100644
@@ -25,7 +25,7 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
-	WARN_ONCE(err != EINVAL,
+	WARN_ONCE(err != EINVAL && err != EBUSY,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, strerror(err));
 

@@ -33,7 +33,7 @@ static int perf_flag_probe(void)
 	fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
 	err = errno;
 
-	if (WARN_ONCE(fd < 0,
+	if (WARN_ONCE(fd < 0 && err != EBUSY,
 		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 		      err, strerror(err)))
 		return -1;
tools/perf/util/evsel.c +6 -0
index 21a373ebea22..180ce82d79ea 100644
@@ -2036,6 +2036,12 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
 	"No APIC? If so then you can boot the kernel with the \"lapic\" boot parameter to force-enable it.");
 #endif
 		break;
+	case EBUSY:
+		if (find_process("oprofiled"))
+			return scnprintf(msg, size,
+	"The PMU counters are busy/taken by another profiler.\n"
+	"We found oprofile daemon running, please stop it and try again.");
+		break;
 	default:
 		break;
 	}
tools/perf/util/util.c +36 -0
index e52e7461911b..b82a93cb1694 100644
@@ -536,3 +536,39 @@ void mem_bswap_64(void *src, int byte_size)
 		++m;
 	}
 }
+
+bool find_process(const char *name)
+{
+	size_t len = strlen(name);
+	DIR *dir;
+	struct dirent *d;
+	int ret = -1;
+
+	dir = opendir(procfs__mountpoint());
+	if (!dir)
+		return -1;
+
+	/* Walk through the directory. */
+	while (ret && (d = readdir(dir)) != NULL) {
+		char path[PATH_MAX];
+		char *data;
+		size_t size;
+
+		if ((d->d_type != DT_DIR) ||
+		     !strcmp(".", d->d_name) ||
+		     !strcmp("..", d->d_name))
+			continue;
+
+		scnprintf(path, sizeof(path), "%s/%s/comm",
+			  procfs__mountpoint(), d->d_name);
+
+		if (filename__read_str(path, &data, &size))
+			continue;
+
+		ret = strncmp(name, data, len);
+		free(data);
+	}
+
+	closedir(dir);
+	return ret ? false : true;
+}
tools/perf/util/util.h +1 -0
index 66864364ccb4..11d977db58a7 100644
@@ -330,4 +330,5 @@ void mem_bswap_64(void *src, int byte_size);
 void mem_bswap_32(void *src, int byte_size);
 
 const char *get_filename_for_perf_kvm(void);
+bool find_process(const char *name);
 #endif /* GIT_COMPAT_UTIL_H */
Signature · 1 line
1.8.3.1
#1 lore raw

Hi Jiri,

Quoted 61 lines · Jiri Olsa

Showing better error message in case we fail to open counters due to the EBUSY error. If we detect oprofile daemon process running, we now display following message for EBUSY error:

  $ perf record ls
  Error:
  The PMU counters are busy/taken by another profiler.
  We found oprofile daemon running, please stop it and try again.

In case oprofiled was not detected the current error message stays:

  $ perf record ls
  Error:
  The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (cycles).
  /bin/dmesg may provide additional information.
  No CONFIG_PERF_EVENTS=y kernel support configured?

Also changing PERF_FLAG_FD_CLOEXEC detection code not to display error in case of EBUSY error, as it currently does:

  $ perf record ls
  Error:
  perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 16 (Device or resource busy)
  perf_event_open(..., 0) failed unexpectedly with error 16 (Device or resource busy)
  The PMU counters are busy/taken by another profiler.
  We found oprofile daemon running, please stop it and try again.
Cc Adrian Hunter <[email protected]>
Cc Arnaldo Carvalho de Melo <[email protected]>
Cc David Ahern <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc William Cohen <[email protected]>
Cc Yann Droneaud <[email protected]>
Signed-off-by Jiri Olsa <[email protected]>
---
 tools/perf/util/cloexec.c |  4 ++--
 tools/perf/util/evsel.c   |  6 ++++++
 tools/perf/util/util.c    | 36 ++++++++++++++++++++++++++++++++++++
 tools/perf/util/util.h    |  1 +
 4 files changed, 45 insertions(+), 2 deletions(-)
tools/perf/util/cloexec.c +1 -1
index c5d05ec17220..dede0c388ed4 100644
@@ -25,7 +25,7 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
-	WARN_ONCE(err != EINVAL,
+	WARN_ONCE(err != EINVAL && err != EBUSY,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, strerror(err));

tools/perf/util/cloexec.c static int perf_flag_probe(void) · line 39

Quoted 8 lines
tools/perf/util/cloexec.c +1 -1
@@ -33,7 +33,7 @@ static int perf_flag_probe(void)
 	fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
 	err = errno;
 
-	if (WARN_ONCE(fd < 0,
+	if (WARN_ONCE(fd < 0 && err != EBUSY,
 		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 		      err, strerror(err)))
 		return -1;

It's definitely possible to shortcut the function if EBUSY is returned by first call to perf_event_open().

tools/perf/util/cloexec.c +3 -0
index dc360ebde745..d5c626d5432a 100644
@@ -25,6 +25,9 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
+	if (err == EBUSY)
+		return -1;
+
 	WARN_ONCE(err != EINVAL,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, strerror(err));

BTW, I'm going to submit a patch to make the function report such warning only once.

Regards.

Signature · 2 lines
Yann Droneaud
OPTEYA
#2 lore raw

PATCH 1/1 perf tools: Fix PERF_FLAG_FD_CLOEXEC flag probing event type open counters due to EBUSY error

Quoted 1 line · Yann Droneaud

Hi Jiri,

SNIP

Quoted 16 lines

Review

Quoted 7 lines
(quoted diff) +1 -1
 	err = errno;
 
-	if (WARN_ONCE(fd < 0,
+	if (WARN_ONCE(fd < 0 && err != EBUSY,
 		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 		      err, strerror(err)))
 		return -1;

It's definitely possible to shortcut the function if EBUSY is returned by first call to perf_event_open().

tools/perf/util/cloexec.c +0 -0
index dc360ebde745..d5c626d5432a 100644

tools/perf/util/cloexec.c static int perf_flag_probe(void) · line 33

Quoted 9 lines
tools/perf/util/cloexec.c +3 -0
@@ -25,6 +25,9 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
+	if (err == EBUSY)
+		return -1;
+
 	WARN_ONCE(err != EINVAL,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, strerror(err));

heh, I haven't realized that your probing event was PERF_COUNT_SW_CPU_CLOCK, which could never be busy and found following bug ;-)

jirka

---
We were using PERF_COUNT_SW_CPU_CLOCK as an probing event type. Using expected PERF_TYPE_SOFTWARE type instead.

Cc Adrian Hunter <[email protected]>
Cc Arnaldo Carvalho de Melo <[email protected]>
Cc David Ahern <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc William Cohen <[email protected]>
Cc Yann Droneaud <[email protected]>
Signed-off-by Jiri Olsa <[email protected]>
---
 tools/perf/util/cloexec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/util/cloexec.c +1 -1
index dc360ebde745..0f7eb0a53d4b 100644
@@ -9,7 +9,7 @@ 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,
+		.type = PERF_TYPE_SOFTWARE,
 		.config = PERF_COUNT_SW_CPU_CLOCK,
 	};
 	int fd;
Signature · 1 line
1.8.3.1
#3 lore raw

Re: [PATCH] perf tools: Fix PERF_FLAG_FD_CLOEXEC flag probing event type open counters due to EBUSY error

Hi,

Quoted 33 lines · Jiri Olsa

On Sat, Aug 02, 2014 at 07:58:25PM +0200, Yann Droneaud wrote:

heh, I haven't realized that your probing event was PERF_COUNT_SW_CPU_CLOCK, which could never be busy and found following bug ;-)

jirka

---
We were using PERF_COUNT_SW_CPU_CLOCK as an probing event type. Using expected PERF_TYPE_SOFTWARE type instead.

Cc Adrian Hunter <[email protected]>
Cc Arnaldo Carvalho de Melo <[email protected]>
Cc David Ahern <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc William Cohen <[email protected]>
Cc Yann Droneaud <[email protected]>
Signed-off-by Jiri Olsa <[email protected]>
---
 tools/perf/util/cloexec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/util/cloexec.c +0 -0
index dc360ebde745..0f7eb0a53d4b 100644

tools/perf/util/cloexec.c static int perf_flag_probe(void) · line 13

Quoted 6 lines
tools/perf/util/cloexec.c +1 -1
@@ -9,7 +9,7 @@ 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,
+		.type = PERF_TYPE_SOFTWARE,
 		.config = PERF_COUNT_SW_CPU_CLOCK,

erf ... I was even not able to copy paste correctly the configuration used in perf_evsel__fallback(), my bad.

Thanks for the fix.

Regards.

Signature · 2 lines
Yann Droneaud
OPTEYA
merge bot
#4 lore raw

[tip:perf/core] perf tools: Fix PERF_FLAG_FD_CLOEXEC flag probing event type open counters due to EBUSY error

In reply to Jiri Olsa
perf tools: Fix PERF_FLAG_FD_CLOEXEC flag probing event type open counters due to EBUSY error
Commit-ID:  038fa0b9739d7f375f3f61a2ce4f78ad44329f66
Gitweb:     http://git.kernel.org/tip/038fa0b9739d7f375f3f61a2ce4f78ad44329f66
Author:     Jiri Olsa <[email protected]>
AuthorDate: Sun, 3 Aug 2014 14:10:36 +0200
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Tue, 12 Aug 2014 12:03:08 -0300

perf tools: Fix PERF_FLAG_FD_CLOEXEC flag probing event type open counters due to EBUSY error

We were using PERF_COUNT_SW_CPU_CLOCK as an probing event type. Using expected PERF_TYPE_SOFTWARE type instead.

Signed-off-by Jiri Olsa <[email protected]>
Cc Adrian Hunter <[email protected]>
Cc David Ahern <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Jiri Olsa <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc William Cohen <[email protected]>
Cc Yann Droneaud <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
---
 tools/perf/util/cloexec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/util/cloexec.c +1 -1
index dede0c3..5073c01 100644
@@ -9,7 +9,7 @@ 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,
+		.type = PERF_TYPE_SOFTWARE,
 		.config = PERF_COUNT_SW_CPU_CLOCK,
 	};
 	int fd;
#5 lore raw

PATCH 1/1 perf tools: report PERF_FLAG_FD_CLOEXEC probing error once

In reply to Jiri Olsa

In case of failure, unrelated to PERF_FLAG_FD_CLOEXEC, perf_flag_probe() reports the error twice. For example:

  $ perf record ls
  Error:
  perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 16 (Device or resource busy)
  perf_event_open(..., 0) failed unexpectedly with error 16 (Device or resource busy)
  The PMU counters are busy/taken by another profiler.
  We found oprofile daemon running, please stop it and try again.

This patch changes the function to only report a second error message when the two calls to perf_even_open(2) fail with different error codes.

Cc Andi Kleen <[email protected]>
Cc Arnaldo Carvalho de Melo <[email protected]>
Cc Ingo Molnar <[email protected]>
Cc Jiri Olsa <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Adrian Hunter <[email protected]>
Cc David Ahern <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc William Cohen <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Reported-by Jiri Olsa <[email protected]>
Signed-off-by Yann Droneaud <[email protected]>
---
 tools/perf/util/cloexec.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)
tools/perf/util/cloexec.c +13 -11
index c5d05ec17220..dc360ebde745 100644
@@ -13,34 +13,36 @@ static int perf_flag_probe(void)
 		.config = PERF_COUNT_SW_CPU_CLOCK,
 	};
 	int fd;
-	int err;
+	int err0, err1;
 
 	/* check cloexec flag */
 	fd = sys_perf_event_open(&attr, 0, -1, -1,
 				 PERF_FLAG_FD_CLOEXEC);
-	err = errno;
+	err0 = errno;
 
 	if (fd >= 0) {
 		close(fd);
 		return 1;
 	}
 
-	WARN_ONCE(err != EINVAL,
+	WARN_ONCE(err0 != EINVAL,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
-		  err, strerror(err));
+		  err0, strerror(err0));
 
 	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
 	fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
-	err = errno;
+	err1 = errno;
 
-	if (WARN_ONCE(fd < 0,
-		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
-		      err, strerror(err)))
-		return -1;
+	if (fd >= 0) {
+		close(fd);
+		return 0;
+	}
 
-	close(fd);
+	WARN_ONCE(err0 != err1,
+		  "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
+		  err1, strerror(err1));
 
-	return 0;
+	return -1;
 }
 
 unsigned long perf_event_open_cloexec_flag(void)
Signature · 1 line
1.9.3
#6 lore raw

Re: [PATCH] perf tools: report PERF_FLAG_FD_CLOEXEC probing error once

Quoted 7 lines · Yann Droneaud

In case of failure, unrelated to PERF_FLAG_FD_CLOEXEC, perf_flag_probe() reports the error twice. For example:

  $ perf record ls
  Error:
  perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 16 (Device or resource busy)
  perf_event_open(..., 0) failed unexpectedly with error 16 (Device or resource busy)

seems ok,
but since your patch is not based on my other patch, please provide the changelog perf out without it

---

Quoted 2 lines

The PMU counters are busy/taken by another profiler. We found oprofile daemon running, please stop it and try again.

---

also, please provide both before and after outputs I'll queue it up with those other 2 patches

thanks,
jirka

merge bot
#7 lore raw
In reply to Jiri Olsa
perf tools: Show better error message in case we fail to open counters due to EBUSY error
Commit-ID:  63914aca8f7e7a75d0ee027af7b1755c69cc1e2c
Gitweb:     http://git.kernel.org/tip/63914aca8f7e7a75d0ee027af7b1755c69cc1e2c
Author:     Jiri Olsa <[email protected]>
AuthorDate: Fri, 1 Aug 2014 17:46:54 +0200
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Tue, 12 Aug 2014 12:03:02 -0300

perf tools: Show better error message in case we fail to open counters due to EBUSY error

Showing better error message in case we fail to open counters due to the EBUSY error. If we detect oprofile daemon process running, we now display following message for EBUSY error:

  $ perf record ls
  Error:
  The PMU counters are busy/taken by another profiler.
  We found oprofile daemon running, please stop it and try again.

In case oprofiled was not detected the current error message stays:

  $ perf record ls
  Error:
  The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (cycles).
  /bin/dmesg may provide additional information.
  No CONFIG_PERF_EVENTS=y kernel support configured?

Also changing PERF_FLAG_FD_CLOEXEC detection code not to display error in case of EBUSY error, as it currently does:

  $ perf record ls
  Error:
  perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 16 (Device or resource busy)
  perf_event_open(..., 0) failed unexpectedly with error 16 (Device or resource busy)
  The PMU counters are busy/taken by another profiler.
  We found oprofile daemon running, please stop it and try again.
Signed-off-by Jiri Olsa <[email protected]>
Cc Adrian Hunter <[email protected]>
Cc David Ahern <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc William Cohen <[email protected]>
Cc Yann Droneaud <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
---
 tools/perf/util/cloexec.c |  4 ++--
 tools/perf/util/evsel.c   |  6 ++++++
 tools/perf/util/util.c    | 36 ++++++++++++++++++++++++++++++++++++
 tools/perf/util/util.h    |  1 +
 4 files changed, 45 insertions(+), 2 deletions(-)
tools/perf/util/cloexec.c +2 -2
index c5d05ec..dede0c3 100644
@@ -25,7 +25,7 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
-	WARN_ONCE(err != EINVAL,
+	WARN_ONCE(err != EINVAL && err != EBUSY,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, strerror(err));
 

@@ -33,7 +33,7 @@ static int perf_flag_probe(void)
 	fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
 	err = errno;
 
-	if (WARN_ONCE(fd < 0,
+	if (WARN_ONCE(fd < 0 && err != EBUSY,
 		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 		      err, strerror(err)))
 		return -1;
tools/perf/util/evsel.c +6 -0
index 92e5235..0c8919d 100644
@@ -2039,6 +2039,12 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
 	"No APIC? If so then you can boot the kernel with the \"lapic\" boot parameter to force-enable it.");
 #endif
 		break;
+	case EBUSY:
+		if (find_process("oprofiled"))
+			return scnprintf(msg, size,
+	"The PMU counters are busy/taken by another profiler.\n"
+	"We found oprofile daemon running, please stop it and try again.");
+		break;
 	default:
 		break;
 	}
tools/perf/util/util.c +36 -0
index e52e746..b82a93c 100644
@@ -536,3 +536,39 @@ void mem_bswap_64(void *src, int byte_size)
 		++m;
 	}
 }
+
+bool find_process(const char *name)
+{
+	size_t len = strlen(name);
+	DIR *dir;
+	struct dirent *d;
+	int ret = -1;
+
+	dir = opendir(procfs__mountpoint());
+	if (!dir)
+		return -1;
+
+	/* Walk through the directory. */
+	while (ret && (d = readdir(dir)) != NULL) {
+		char path[PATH_MAX];
+		char *data;
+		size_t size;
+
+		if ((d->d_type != DT_DIR) ||
+		     !strcmp(".", d->d_name) ||
+		     !strcmp("..", d->d_name))
+			continue;
+
+		scnprintf(path, sizeof(path), "%s/%s/comm",
+			  procfs__mountpoint(), d->d_name);
+
+		if (filename__read_str(path, &data, &size))
+			continue;
+
+		ret = strncmp(name, data, len);
+		free(data);
+	}
+
+	closedir(dir);
+	return ret ? false : true;
+}
tools/perf/util/util.h +1 -0
index 38af775..03a1ea2 100644
@@ -346,4 +346,5 @@ void mem_bswap_64(void *src, int byte_size);
 void mem_bswap_32(void *src, int byte_size);
 
 const char *get_filename_for_perf_kvm(void);
+bool find_process(const char *name);
 #endif /* GIT_COMPAT_UTIL_H */