linux-kernel - [PATCH 1/1] perf stat: handle ENXIO error for perf_event

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Message-Id: <1336585439-32378-2-git-send-email-acme@infradead.org>
Date:	Wed,  9 May 2012 14:43:59 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 1/1] perf stat: handle ENXIO error for perf_event_open

From: David Ahern <dsahern@...il.com>

perf stat on PPC currently fails to run:

$ perf stat -- sleep 1
  Error: open_counter returned with 6 (No such device or address). /bin/dmesg may provide additional information.

  Fatal: Not all events could be opened.

The problem is that until 2.6.37 (behavior changed with commit b0a873e)
perf on PPC returns ENXIO when hw_perf_event_init() fails. With this
patch we get the expected behavior:

$ perf stat -v -- sleep 1
cycles event is not supported by the kernel.
stalled-cycles-frontend event is not supported by the kernel.
stalled-cycles-backend event is not supported by the kernel.
instructions event is not supported by the kernel.
branches event is not supported by the kernel.
branch-misses event is not supported by the kernel.

...

Signed-off-by: David Ahern <dsahern@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1336490956-57145-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-stat.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 4532a78..1e5e9b2 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -488,8 +488,13 @@ static int run_perf_stat(int argc __used, const char **argv)
 
 	list_for_each_entry(counter, &evsel_list->entries, node) {
 		if (create_perf_stat_counter(counter, first) < 0) {
+			/*
+			 * PPC returns ENXIO for HW counters until 2.6.37
+			 * (behavior changed with commit b0a873e).
+			 */
 			if (errno == EINVAL || errno == ENOSYS ||
-			    errno == ENOENT || errno == EOPNOTSUPP) {
+			    errno == ENOENT || errno == EOPNOTSUPP ||
+			    errno == ENXIO) {
 				if (verbose)
 					ui__warning("%s event is not supported by the kernel.\n",
 						    event_name(counter));
-- 
1.7.9.2.358.g22243

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