diff options
| -rw-r--r-- | include/linux/lockdep.h | 22 | ||||
| -rw-r--r-- | kernel/locking/lockdep.c | 82 |
2 files changed, 77 insertions, 27 deletions
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index c75eedd55af5..651cc61af041 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -325,6 +325,19 @@ struct hist_lock { */ struct cross_lock { /* + * When more than one acquisition of crosslocks are overlapped, + * we have to perform commit for them based on cross_gen_id of + * the first acquisition, which allows us to add more true + * dependencies. + * + * Moreover, when no acquisition of a crosslock is in progress, + * we should not perform commit because the lock might not exist + * any more, which might cause incorrect memory access. So we + * have to track the number of acquisitions of a crosslock. + */ + int nr_acquire; + + /* * Seperate hlock instance. This will be used at commit step. * * TODO: Use a smaller data structure containing only necessary @@ -547,9 +560,16 @@ extern void lockdep_init_map_crosslock(struct lockdep_map *lock, int subclass); extern void lock_commit_crosslock(struct lockdep_map *lock); +/* + * What we essencially have to initialize is 'nr_acquire'. Other members + * will be initialized in add_xlock(). + */ +#define STATIC_CROSS_LOCK_INIT() \ + { .nr_acquire = 0,} + #define STATIC_CROSS_LOCKDEP_MAP_INIT(_name, _key) \ { .map.name = (_name), .map.key = (void *)(_key), \ - .map.cross = 1, } + .map.cross = 1, .xlock = STATIC_CROSS_LOCK_INIT(), } /* * To initialize a lockdep_map statically use this macro. diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index eda8114ef793..7f97871d48d5 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -4867,11 +4867,28 @@ static int add_xlock(struct held_lock *hlock) xlock = &((struct lockdep_map_cross *)hlock->instance)->xlock; + /* + * When acquisitions for a crosslock are overlapped, we use + * nr_acquire to perform commit for them, based on cross_gen_id + * of the first acquisition, which allows to add additional + * dependencies. + * + * Moreover, when no acquisition of a crosslock is in progress, + * we should not perform commit because the lock might not exist + * any more, which might cause incorrect memory access. So we + * have to track the number of acquisitions of a crosslock. + * + * depend_after() is necessary to initialize only the first + * valid xlock so that the xlock can be used on its commit. + */ + if (xlock->nr_acquire++ && depend_after(&xlock->hlock)) + goto unlock; + gen_id = (unsigned int)atomic_inc_return(&cross_gen_id); xlock->hlock = *hlock; xlock->hlock.gen_id = gen_id; +unlock: graph_unlock(); - return 1; } @@ -4967,35 +4984,37 @@ static void commit_xhlocks(struct cross_lock *xlock) if (!graph_lock()) return; - for (i = 0; i < MAX_XHLOCKS_NR; i++) { - struct hist_lock *xhlock = &xhlock(cur - i); + if (xlock->nr_acquire) { + for (i = 0; i < MAX_XHLOCKS_NR; i++) { + struct hist_lock *xhlock = &xhlock(cur - i); - if (!xhlock_valid(xhlock)) - break; + if (!xhlock_valid(xhlock)) + break; - if (before(xhlock->hlock.gen_id, xlock->hlock.gen_id)) - break; + if (before(xhlock->hlock.gen_id, xlock->hlock.gen_id)) + break; - if (!same_context_xhlock(xhlock)) - break; + if (!same_context_xhlock(xhlock)) + break; - /* - * Filter out the cases that the ring buffer was - * overwritten and the previous entry has a bigger - * hist_id than the following one, which is impossible - * otherwise. - */ - if (unlikely(before(xhlock->hist_id, prev_hist_id))) - break; + /* + * Filter out the cases that the ring buffer was + * overwritten and the previous entry has a bigger + * hist_id than the following one, which is impossible + * otherwise. + */ + if (unlikely(before(xhlock->hist_id, prev_hist_id))) + break; - prev_hist_id = xhlock->hist_id; + prev_hist_id = xhlock->hist_id; - /* - * commit_xhlock() returns 0 with graph_lock already - * released if fail. - */ - if (!commit_xhlock(xlock, xhlock)) - return; + /* + * commit_xhlock() returns 0 with graph_lock already + * released if fail. + */ + if (!commit_xhlock(xlock, xhlock)) + return; + } } graph_unlock(); @@ -5039,16 +5058,27 @@ void lock_commit_crosslock(struct lockdep_map *lock) EXPORT_SYMBOL_GPL(lock_commit_crosslock); /* - * Return: 1 - crosslock, done; + * Return: 0 - failure; + * 1 - crosslock, done; * 2 - normal lock, continue to held_lock[] ops. */ static int lock_release_crosslock(struct lockdep_map *lock) { - return cross_lock(lock) ? 1 : 2; + if (cross_lock(lock)) { + if (!graph_lock()) + return 0; + ((struct lockdep_map_cross *)lock)->xlock.nr_acquire--; + graph_unlock(); + return 1; + } + return 2; } static void cross_init(struct lockdep_map *lock, int cross) { + if (cross) + ((struct lockdep_map_cross *)lock)->xlock.nr_acquire = 0; + lock->cross = cross; /* |