Found by Jeff King.
Signed-off-by: Nicolas Pitre <nico@xxxxxxx>
---
On Mon, 10 Sep 2007, Jeff King wrote:
> I think I am seeing something like this:
> - thread A gets data_request lock
> - thread A unlocks data_provider lock, signaling provider
> - thread A blocks getting data_ready lock
> - provider allocates work for A, unlocking data_ready to signal A
> - provider unlocks data_request lock, ready for next request
> - thread B gets data_request lock
> - thread B unlocks data_provider lock, signaling provider
> - thread B gets data_ready lock, because A still hasn't run yet
> - thread B tries to run on bogus data, since provider hasn't actually
> allocated any work yet
Doh!
OK I prefer the following fix as it doesn't need an additional lock.
Junio: you might fold this with patch 1/3 if you wish.
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 42698d2..af12e45 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -1597,6 +1597,7 @@ static void *threaded_find_deltas(void *arg)
data_requester = me;
pthread_mutex_unlock(&data_provider);
pthread_mutex_lock(&data_ready);
+ pthread_mutex_unlock(&data_request);
if (!me->list_size)
return NULL;
@@ -1609,7 +1610,7 @@ static void *threaded_find_deltas(void *arg)
static void ll_find_deltas(struct object_entry **list, unsigned list_size,
int window, int depth, unsigned *processed)
{
- struct thread_params p[delta_search_threads];
+ struct thread_params *target, p[delta_search_threads];
int i, ret;
unsigned chunk_size;
@@ -1645,17 +1646,17 @@ static void ll_find_deltas(struct object_entry **list, unsigned list_size,
sublist_size++;
pthread_mutex_lock(&data_provider);
- data_requester->list = list;
- data_requester->list_size = sublist_size;
+ target = data_requester;
+ target->list = list;
+ target->list_size = sublist_size;
pthread_mutex_unlock(&data_ready);
list += sublist_size;
list_size -= sublist_size;
if (!sublist_size) {
- pthread_join(data_requester->thread, NULL);
+ pthread_join(target->thread, NULL);
i--;
}
- pthread_mutex_unlock(&data_request);
} while (i);
}
-
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