pack-objects: move read mutex to packing_data struct

ac77d0c37 ("pack-objects: shrink size field in struct object_entry",
2018-04-14) added an extra usage of read_lock/read_unlock in the newly
introduced oe_get_size_slow for thread safety in parallel calls to
try_delta(). Unfortunately oe_get_size_slow is also used in serial
code, some of which is called before the first invocation of
ll_find_deltas. As such the read mutex is not guaranteed to be
initialized.

Resolve this by moving the read mutex to packing_data and initializing
it in prepare_packing_data which is initialized in cmd_pack_objects.

Signed-off-by: Patrick Hogg <phogg@novamoon.net>
Reviewed-by: Duy Nguyen <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 411aefd6875b2d35ee4a12d1a043ba50027021b3..506061b4c946509c9798c9315138e401ef6cd368 100644 (file)
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1954,9 +1954,8 @@ static int delta_cacheable(unsigned long src_size, unsigned long trg_size,
 }
 
 /* Protect access to object database */
-static pthread_mutex_t read_mutex;
-#define read_lock()            pthread_mutex_lock(&read_mutex)
-#define read_unlock()          pthread_mutex_unlock(&read_mutex)
+#define read_lock()            packing_data_read_lock(&to_pack)
+#define read_unlock()          packing_data_read_unlock(&to_pack)
 
 /* Protect delta_cache_size */
 static pthread_mutex_t cache_mutex;
@@ -2381,7 +2380,6 @@ static pthread_cond_t progress_cond;
  */
 static void init_threaded_search(void)
 {
-       init_recursive_mutex(&read_mutex);
        pthread_mutex_init(&cache_mutex, NULL);
        pthread_mutex_init(&progress_mutex, NULL);
        pthread_cond_init(&progress_cond, NULL);
@@ -2392,7 +2390,6 @@ static void cleanup_threaded_search(void)
 {
        set_try_to_free_routine(old_try_to_free_routine);
        pthread_cond_destroy(&progress_cond);
-       pthread_mutex_destroy(&read_mutex);
        pthread_mutex_destroy(&cache_mutex);
        pthread_mutex_destroy(&progress_mutex);
 }

diff --git a/pack-objects.c b/pack-objects.c
index b6cdbb0166fb5a3d6af3cfda2e7e259e3d54abe8..3554c43ac281c642c4869ecdac4487b0b4ccc562 100644 (file)
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -150,6 +150,7 @@ void prepare_packing_data(struct packing_data *pdata)
                                                   1UL << OE_DELTA_SIZE_BITS);
 #ifndef NO_PTHREADS
        pthread_mutex_init(&pdata->lock, NULL);
+       init_recursive_mutex(&pdata->read_lock);
 #endif
 }
 

diff --git a/pack-objects.h b/pack-objects.h
index dc869f26c2b753593a875f275d896933b7723b31..0a038e3bc6453bba5a2519b71b871d286d98acfb 100644 (file)
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -146,6 +146,7 @@ struct packing_data {
        struct packed_git **in_pack;
 
        pthread_mutex_t lock;
+       pthread_mutex_t read_lock;
 
        /*
         * This list contains entries for bases which we know the other side
@@ -174,6 +175,15 @@ static inline void packing_data_unlock(struct packing_data *pdata)
        pthread_mutex_unlock(&pdata->lock);
 }
 
+static inline void packing_data_read_lock(struct packing_data *pdata)
+{
+       pthread_mutex_lock(&pdata->read_lock);
+}
+static inline void packing_data_read_unlock(struct packing_data *pdata)
+{
+       pthread_mutex_unlock(&pdata->read_lock);
+}
+
 struct object_entry *packlist_alloc(struct packing_data *pdata,
                                    const unsigned char *sha1,
                                    uint32_t index_pos);