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Subject[tip:perf/core] perf mmap: Be consistent when checking for an unmaped ring buffer
Commit-ID:  895e3b06fc2ce438adc62cb13d31ea001dcfda16
Gitweb: https://git.kernel.org/tip/895e3b06fc2ce438adc62cb13d31ea001dcfda16
Author: Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Mon, 26 Mar 2018 11:42:15 -0300
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 27 Mar 2018 13:13:38 -0300

perf mmap: Be consistent when checking for an unmaped ring buffer

The previous patch is insufficient to cure the reported 'perf trace'
segfault, as it only cures the perf_mmap__read_done() case, moving the
segfault to perf_mmap__read_init() functio, fix it by doing the same
refcount check.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 8872481bd048 ("perf mmap: Introduce perf_mmap__read_init()")
Link: https://lkml.kernel.org/r/20180326144127.GF18897@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/mmap.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index f6cfc52ff1fe..fc832676a798 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -234,7 +234,7 @@ static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end)
/*
* Report the start and end of the available data in ringbuffer
*/
-int perf_mmap__read_init(struct perf_mmap *md)
+static int __perf_mmap__read_init(struct perf_mmap *md)
{
u64 head = perf_mmap__read_head(md);
u64 old = md->prev;
@@ -268,6 +268,17 @@ int perf_mmap__read_init(struct perf_mmap *md)
return 0;
}

+int perf_mmap__read_init(struct perf_mmap *map)
+{
+ /*
+ * Check if event was unmapped due to a POLLHUP/POLLERR.
+ */
+ if (!refcount_read(&map->refcnt))
+ return -ENOENT;
+
+ return __perf_mmap__read_init(map);
+}
+
int perf_mmap__push(struct perf_mmap *md, void *to,
int push(void *to, void *buf, size_t size))
{
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