perf evlist: Make event_copy local to mmaps
I am getting segfaults *after* the time sorting of perf samples where
the event type is off the charts:
(gdb) bt
\#0 0x0807b1b2 in hists__inc_nr_events (hists=0x80a99c4, type=1163281902) at util/hist.c:1225
\#1 0x08070795 in perf_session_deliver_event (session=0x80a9b90, event=0xf7a6aff8, sample=0xffffc318, tool=0xffffc520,
file_offset=0) at util/session.c:884
\#2 0x0806f9b9 in flush_sample_queue (s=0x80a9b90, tool=0xffffc520) at util/session.c:555
\#3 0x0806fc53 in process_finished_round (tool=0xffffc520, event=0x0, session=0x80a9b90) at util/session.c:645
This is bizarre because the event has already been processed once --
before it was added to the samples queue -- and the event was found to
be sane at that time.
There seem to be 2 causes:
1. perf_evlist__mmap_read updates the read location even though there
are outstanding references to events sitting in the mmap buffers via the
ordered samples queue.
2. There is a single evlist->event_copy for all evlist entries.
event_copy is used to handle an event wrapping at the mmap buffer
boundary.
This patch addresses the second problem - making event_copy local to
each perf_mmap. With this change my highly repeatable use case no longer
fails.
The first problem is much more complicated and will be the subject of a
future patch.
Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1360098762-61827-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 73579a2..2dd07bd 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -17,6 +17,13 @@
#define PERF_EVLIST__HLIST_BITS 8
#define PERF_EVLIST__HLIST_SIZE (1 << PERF_EVLIST__HLIST_BITS)
+struct perf_mmap {
+ void *base;
+ int mask;
+ unsigned int prev;
+ union perf_event event_copy;
+};
+
struct perf_evlist {
struct list_head entries;
struct hlist_head heads[PERF_EVLIST__HLIST_SIZE];
@@ -30,7 +37,6 @@
pid_t pid;
} workload;
bool overwrite;
- union perf_event event_copy;
struct perf_mmap *mmap;
struct pollfd *pollfd;
struct thread_map *threads;
@@ -136,4 +142,25 @@
}
size_t perf_evlist__fprintf(struct perf_evlist *evlist, FILE *fp);
+
+static inline unsigned int perf_mmap__read_head(struct perf_mmap *mm)
+{
+ struct perf_event_mmap_page *pc = mm->base;
+ int head = pc->data_head;
+ rmb();
+ return head;
+}
+
+static inline void perf_mmap__write_tail(struct perf_mmap *md,
+ unsigned long tail)
+{
+ struct perf_event_mmap_page *pc = md->base;
+
+ /*
+ * ensure all reads are done before we write the tail out.
+ */
+ /* mb(); */
+ pc->data_tail = tail;
+}
+
#endif /* __PERF_EVLIST_H */