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Make the mutex n_waiting_thds field a C11-style atomic

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This commit is contained in:
David Goldblatt 2017-04-04 18:34:01 -07:00 committed by David Goldblatt
parent 492a941f49
commit 5dcc13b342
4 changed files with 19 additions and 7 deletions
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14
include/jemalloc/internal/mutex_inlines.h
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@ -40,7 +40,12 @@ malloc_mutex_prof_merge(mutex_prof_data_t *sum, mutex_prof_data_t *data) {
if (sum->max_n_thds < data->max_n_thds) {
sum->max_n_thds = data->max_n_thds;
}
sum->n_waiting_thds += data->n_waiting_thds;
uint32_t cur_n_waiting_thds = atomic_load_u32(&sum->n_waiting_thds,
ATOMIC_RELAXED);
uint32_t new_n_waiting_thds = cur_n_waiting_thds + atomic_load_u32(
&data->n_waiting_thds, ATOMIC_RELAXED);
atomic_store_u32(&sum->n_waiting_thds, new_n_waiting_thds,
ATOMIC_RELAXED);
sum->n_owner_switches += data->n_owner_switches;
sum->n_lock_ops += data->n_lock_ops;
}
@ -91,9 +96,14 @@ malloc_mutex_prof_read(tsdn_t *tsdn, mutex_prof_data_t *data,
/* Can only read holding the mutex. */
malloc_mutex_assert_owner(tsdn, mutex);
/*
* Not *really* allowed (we shouldn't be doing non-atomic loads of
* atomic data), but the mutex protection makes this safe, and writing
* a member-for-member copy is tedious for this situation.
*/
*data = *source;
/* n_wait_thds is not reported (modified w/o locking). */
data->n_waiting_thds = 0;
atomic_store_u32(&data->n_waiting_thds, 0, ATOMIC_RELAXED);
}
#endif

2
include/jemalloc/internal/mutex_structs.h
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@ -17,7 +17,7 @@ struct mutex_prof_data_s {
/* Max # of threads waiting for the mutex at the same time. */
uint32_t max_n_thds;
/* Current # of threads waiting on the lock. Atomic synced. */
uint32_t n_waiting_thds;
atomic_u32_t n_waiting_thds;
/*
* Data touched on the fast path. These are modified right after we

3
include/jemalloc/internal/mutex_types.h
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@ -35,7 +35,8 @@ typedef struct malloc_mutex_s malloc_mutex_t;
#endif
#define LOCK_PROF_DATA_INITIALIZER \
{NSTIME_ZERO_INITIALIZER, NSTIME_ZERO_INITIALIZER, 0, 0, 0, 0, 0, NULL, 0}
{NSTIME_ZERO_INITIALIZER, NSTIME_ZERO_INITIALIZER, 0, 0, 0, \
ATOMIC_INIT(0), 0, NULL, 0}
#ifdef _WIN32
# define MALLOC_MUTEX_INITIALIZER

7
src/mutex.c
View File

@ -93,10 +93,11 @@ label_spin_done:
/* Copy before to after to avoid clock skews. */
nstime_t after;
nstime_copy(&after, &before);
uint32_t n_thds = atomic_add_u32(&data->n_waiting_thds, 1);
uint32_t n_thds = atomic_fetch_add_u32(&data->n_waiting_thds, 1,
ATOMIC_RELAXED) + 1;
/* One last try as above two calls may take quite some cycles. */
if (!malloc_mutex_trylock(mutex)) {
atomic_sub_u32(&data->n_waiting_thds, 1);
atomic_fetch_sub_u32(&data->n_waiting_thds, 1, ATOMIC_RELAXED);
data->n_spin_acquired++;
return;
}
@ -104,7 +105,7 @@ label_spin_done:
/* True slow path. */
malloc_mutex_lock_final(mutex);
/* Update more slow-path only counters. */
atomic_sub_u32(&data->n_waiting_thds, 1);
atomic_fetch_sub_u32(&data->n_waiting_thds, 1, ATOMIC_RELAXED);
nstime_update(&after);
nstime_t delta;