Hi,
While running valgrind's drd on my app, I ran into a bunch of race
conditions on the global variable event_debug_mode_too_late. The
questionable assignment happens in a bunch of macros starting on
event.c:195 in libevent-2.0.8-rc
The two threads involved are a server thread and a client thread which
share no event_base. Their event loops are separate; they communicate
only through the proper channels, but I was getting races between
event_del() in one thread and various other locations in the other
thread.
I have an ugly patch below which moves the event_debug_mode_too_late
assignment in event.c inside the EVLOCK_UNLOCK( _event_debug_map_lock,
0 ), which makes all of these race conditions disappear from
valgrind's drd, but I am not sure if it is correct to patch in this
manner.
- Ken
*** event.c 2010-11-19 03:42:03.838376765 +0800
--- event.new.c 2010-11-19 03:41:48.377127426 +0800
***************
*** 209,217 ****
dent->added = 0; \
HT_INSERT(event_debug_map, &global_debug_map, dent); \
} \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
- event_debug_mode_too_late = 1; \
} while (0)
/* Macro: record that ev is no longer setup */
#define _event_debug_note_teardown(ev) do { \
--- 209,217 ----
dent->added = 0; \
HT_INSERT(event_debug_map, &global_debug_map, dent); \
} \
+ event_debug_mode_too_late = 1; \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
} while (0)
/* Macro: record that ev is no longer setup */
#define _event_debug_note_teardown(ev) do { \
***************
*** 222,230 ****
dent = HT_REMOVE(event_debug_map, &global_debug_map, &find); \
if (dent) \
mm_free(dent); \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
- event_debug_mode_too_late = 1; \
} while (0)
/* Macro: record that ev is now added */
#define _event_debug_note_add(ev) do { \
--- 222,230 ----
dent = HT_REMOVE(event_debug_map, &global_debug_map, &find); \
if (dent) \
mm_free(dent); \
+ event_debug_mode_too_late = 1; \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
} while (0)
/* Macro: record that ev is now added */
#define _event_debug_note_add(ev) do { \
***************
*** 240,248 ****
"%s: noting an add on a non-setup event %p", \
__func__, (ev)); \
} \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
- event_debug_mode_too_late = 1; \
} while (0)
/* Macro: record that ev is no longer added */
#define _event_debug_note_del(ev) do {
\
--- 240,248 ----
"%s: noting an add on a non-setup event %p", \
__func__, (ev)); \
} \
+ event_debug_mode_too_late = 1; \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
} while (0)
/* Macro: record that ev is no longer added */
#define _event_debug_note_del(ev) do {
\
***************
*** 258,266 ****
"%s: noting a del on a non-setup event %p", \
__func__, (ev)); \
} \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
- event_debug_mode_too_late = 1; \
} while (0)
/* Macro: assert that ev is setup (i.e., okay to add or inspect) */
#define _event_debug_assert_is_setup(ev) do { \
--- 258,266 ----
"%s: noting a del on a non-setup event %p", \
__func__, (ev)); \
} \
+ event_debug_mode_too_late = 1; \
EVLOCK_UNLOCK(_event_debug_map_lock, 0); \
} \
} while (0)
/* Macro: assert that ev is setup (i.e., okay to add or inspect) */
#define _event_debug_assert_is_setup(ev) do { \
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