diff options
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 42 |
1 files changed, 31 insertions, 11 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 9a0b579c40c..575d092fa74 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -128,6 +128,7 @@ struct worker { }; struct work_struct *current_work; /* L: work being processed */ + work_func_t current_func; /* L: current_work's fn */ struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */ struct list_head scheduled; /* L: scheduled works */ struct task_struct *task; /* I: worker task */ @@ -838,7 +839,8 @@ static struct worker *__find_worker_executing_work(struct global_cwq *gcwq, struct hlist_node *tmp; hlist_for_each_entry(worker, tmp, bwh, hentry) - if (worker->current_work == work) + if (worker->current_work == work && + worker->current_func == work->func) return worker; return NULL; } @@ -848,9 +850,27 @@ static struct worker *__find_worker_executing_work(struct global_cwq *gcwq, * @gcwq: gcwq of interest * @work: work to find worker for * - * Find a worker which is executing @work on @gcwq. This function is - * identical to __find_worker_executing_work() except that this - * function calculates @bwh itself. + * Find a worker which is executing @work on @gcwq by searching + * @gcwq->busy_hash which is keyed by the address of @work. For a worker + * to match, its current execution should match the address of @work and + * its work function. This is to avoid unwanted dependency between + * unrelated work executions through a work item being recycled while still + * being executed. + * + * This is a bit tricky. A work item may be freed once its execution + * starts and nothing prevents the freed area from being recycled for + * another work item. If the same work item address ends up being reused + * before the original execution finishes, workqueue will identify the + * recycled work item as currently executing and make it wait until the + * current execution finishes, introducing an unwanted dependency. + * + * This function checks the work item address, work function and workqueue + * to avoid false positives. Note that this isn't complete as one may + * construct a work function which can introduce dependency onto itself + * through a recycled work item. Well, if somebody wants to shoot oneself + * in the foot that badly, there's only so much we can do, and if such + * deadlock actually occurs, it should be easy to locate the culprit work + * function. * * CONTEXT: * spin_lock_irq(gcwq->lock). @@ -1811,7 +1831,6 @@ __acquires(&gcwq->lock) struct global_cwq *gcwq = cwq->gcwq; struct hlist_head *bwh = busy_worker_head(gcwq, work); bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE; - work_func_t f = work->func; int work_color; struct worker *collision; #ifdef CONFIG_LOCKDEP @@ -1840,6 +1859,7 @@ __acquires(&gcwq->lock) debug_work_deactivate(work); hlist_add_head(&worker->hentry, bwh); worker->current_work = work; + worker->current_func = work->func; worker->current_cwq = cwq; work_color = get_work_color(work); @@ -1877,7 +1897,7 @@ __acquires(&gcwq->lock) lock_map_acquire_read(&cwq->wq->lockdep_map); lock_map_acquire(&lockdep_map); trace_workqueue_execute_start(work); - f(work); + worker->current_func(work); /* * While we must be careful to not use "work" after this, the trace * point will only record its address. @@ -1887,11 +1907,10 @@ __acquires(&gcwq->lock) lock_map_release(&cwq->wq->lockdep_map); if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { - printk(KERN_ERR "BUG: workqueue leaked lock or atomic: " - "%s/0x%08x/%d\n", - current->comm, preempt_count(), task_pid_nr(current)); - printk(KERN_ERR " last function: "); - print_symbol("%s\n", (unsigned long)f); + pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n" + " last function: %pf\n", + current->comm, preempt_count(), task_pid_nr(current), + worker->current_func); debug_show_held_locks(current); dump_stack(); } @@ -1905,6 +1924,7 @@ __acquires(&gcwq->lock) /* we're done with it, release */ hlist_del_init(&worker->hentry); worker->current_work = NULL; + worker->current_func = NULL; worker->current_cwq = NULL; cwq_dec_nr_in_flight(cwq, work_color, false); } |