[PATCH] perf tool cgroup: initialize cgroup refcnt with refcount_set

From: David Carrillo-Cisneros
Date: Thu Jun 01 2017 - 16:02:59 EST


Atomic reference counters were replaced by refcount_t in
commit 79c5fe6db8c7 ("perf/core: Fix error handling in perf_event_alloc()")

In util/cgroup.c atomic_inc was replaced by refcount_inc, but the latter
is not mean to initiliaze refcounts with zero value. Add a path
to initialize cgrp->refcnt == 0 using refcount_set.

Before this patch:

$ perf stat -e cycles -C 0 -G /
perf_before: /usr/local/.../tools/include/linux/refcount.h:108: refcount_inc: Assertion `!(!refcount_inc_not_zero(r))' failed.
Aborted (core dumped)

After this patch:

$ perf stat -e cycles -C 0 -G /
Performance counter stats for 'CPU(s) 0':
17,516,664 cycles /

Signed-off-by: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
Change-Id: I8f00f61aaecce876e7df448bd7f850b20db13ef1
---
tools/perf/util/cgroup.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c
index 03347748f3fa..7bbc19b3caf3 100644
--- a/tools/perf/util/cgroup.c
+++ b/tools/perf/util/cgroup.c
@@ -133,7 +133,10 @@ static int add_cgroup(struct perf_evlist *evlist, char *str)

return -1;
found:
- refcount_inc(&cgrp->refcnt);
+ if (refcount_read(&cgrp->refcnt) == 0)
+ refcount_set(&cgrp->refcnt, 1);
+ else
+ refcount_inc(&cgrp->refcnt);
counter->cgrp = cgrp;
return 0;
}
--
2.13.0.219.gdb65acc882-goog