linux-kernel - [PATCH] perf, tools: Fall weak group back even for EBADF

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Date:   Tue,  5 Sep 2017 14:13:24 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     acme@...nel.org
Cc:     jolsa@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH] perf, tools: Fall weak group back even for EBADF

From: Andi Kleen <ak@...ux.intel.com>

It's not possible to run a package event and a per cpu event in
the same group. This is used by some of the power metrics.
They work correctly when not using a group.

Normally weak groups should handle that, but in this case EBADF
is returned instead of the normal EINVAL.

strace -e perf_event_open ./perf stat -v -e '{cstate_pkg/c2-residency/,msr/tsc/}:W' -a sleep 1
Using CPUID GenuineIntel-6-3E
perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, PERF_FLAG_FD_CLOEXEC) = -1 EINVAL (Invalid argument)
perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = -1 EINVAL (Invalid argument)
perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = -1 EINVAL (Invalid argument)
perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = -1 EINVAL (Invalid argument)
perf_event_open({type=0x17 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, -1, 0) = 3
perf_event_open({type=0x7 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 0, 3, 0) = 4
perf_event_open({type=0x7 /* PERF_TYPE_??? */, size=PERF_ATTR_SIZE_VER5, config=0, ...}, -1, 1, 0, 0) = -1 EBADF (Bad file descriptor)

and perf errors out.

Make weak groups trigger a fall back for EBADF too. Then this case works correctly:

$ ./perf stat -v -e '{cstate_pkg/c2-residency/,msr/tsc/}:W' -a sleep 1
Using CPUID GenuineIntel-6-3E
Weak group for cstate_pkg/c2-residency//2 failed
cstate_pkg/c2-residency/: 476709882 1000598460 1000598460
msr/tsc/: 39625837911 12007369110 12007369110

 Performance counter stats for 'system wide':

       476,709,882      cstate_pkg/c2-residency/
    39,625,837,911      msr/tsc/

       1.000697588 seconds time elapsed

This fixes perf stat -M Power ...

$ ./perf stat -M Power --metric-only -a sleep 1

 Performance counter stats for 'system wide':

Turbo_Utilization    C3_Core_Residency    C6_Core_Residency    C7_Core_Residency    C2_Pkg_Residency     C3_Pkg_Residency     C6_Pkg_Residency     C7_Pkg_Residency
     1.0                 0.7                30.0                 0.0                 0.9                 0.1                 0.4                 0.0

       1.001240740 seconds time elapsed

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 tools/perf/builtin-stat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 60206a1e03aa..1929f92c824b 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -656,7 +656,7 @@ static int __run_perf_stat(int argc, const char **argv)
 		if (create_perf_stat_counter(counter) < 0) {
 
 			/* Weak group failed. Reset the group. */
-			if (errno == EINVAL &&
+			if ((errno == EINVAL || errno == EBADF) &&
 			    counter->leader != counter &&
 			    counter->weak_group) {
 				counter = reset_weak_group(counter);
-- 
2.9.5