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perf evlist: Make event_copy local to mmaps

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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>
This commit is contained in:
David Ahern 2013-02-05 14:12:42 -07:00 committed by Arnaldo Carvalho de Melo
parent 5936f54d6c
commit 0479b8b9cf
3 changed files with 30 additions and 29 deletions
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26
tools/perf/perf.h
View File

@ -103,32 +103,6 @@
#include "util/types.h"
#include <stdbool.h>
struct perf_mmap {
void *base;
int mask;
unsigned int prev;
};
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;
}
/*
* prctl(PR_TASK_PERF_EVENTS_DISABLE) will (cheaply) disable all
* counters in the current task.

4
tools/perf/util/evlist.c
View File

@ -375,7 +375,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
if ((old & md->mask) + size != ((old + size) & md->mask)) {
unsigned int offset = old;
unsigned int len = min(sizeof(*event), size), cpy;
void *dst = &evlist->event_copy;
void *dst = &md->event_copy;
do {
cpy = min(md->mask + 1 - (offset & md->mask), len);
@ -385,7 +385,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
len -= cpy;
} while (len);
event = &evlist->event_copy;
event = &md->event_copy;
}
old += size;

29
tools/perf/util/evlist.h
View File

@ -17,6 +17,13 @@ struct perf_record_opts;
#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 @@ struct perf_evlist {
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 @@ static inline struct perf_evsel *perf_evlist__last(struct perf_evlist *evlist)
}
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 */