diff options
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 8ad214dc15a9..c0331891dec1 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2093,7 +2093,28 @@ __acquires(&pool->lock) lock_map_acquire(&pwq->wq->lockdep_map); lock_map_acquire(&lockdep_map); - crossrelease_hist_start(XHLOCK_PROC); + /* + * Strictly speaking we should do start(PROC) without holding any + * locks, that is, before these two lock_map_acquire()'s. + * + * However, that would result in: + * + * A(W1) + * WFC(C) + * A(W1) + * C(C) + * + * Which would create W1->C->W1 dependencies, even though there is no + * actual deadlock possible. There are two solutions, using a + * read-recursive acquire on the work(queue) 'locks', but this will then + * hit the lockdep limitation on recursive locks, or simly discard + * these locks. + * + * AFAICT there is no possible deadlock scenario between the + * flush_work() and complete() primitives (except for single-threaded + * workqueues), so hiding them isn't a problem. + */ + crossrelease_hist_start(XHLOCK_PROC, true); trace_workqueue_execute_start(work); worker->current_func(work); /* |