diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/workqueue.c | 39 |
1 files changed, 31 insertions, 8 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index acd417b..d24a411 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -137,6 +137,7 @@ 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 */ @@ -861,9 +862,27 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags) * @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). @@ -878,8 +897,10 @@ static struct worker *find_worker_executing_work(struct global_cwq *gcwq, struct worker *worker; struct hlist_node *tmp; - hash_for_each_possible(gcwq->busy_hash, worker, tmp, hentry, (unsigned long)work) - if (worker->current_work == work) + hash_for_each_possible(gcwq->busy_hash, worker, tmp, hentry, + (unsigned long)work) + if (worker->current_work == work && + worker->current_func == work->func) return worker; return NULL; @@ -2114,7 +2135,6 @@ __acquires(&gcwq->lock) struct worker_pool *pool = worker->pool; struct global_cwq *gcwq = pool->gcwq; bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE; - work_func_t f = work->func; int work_color; struct worker *collision; #ifdef CONFIG_LOCKDEP @@ -2154,6 +2174,7 @@ __acquires(&gcwq->lock) debug_work_deactivate(work); hash_add(gcwq->busy_hash, &worker->hentry, (unsigned long)worker); worker->current_work = work; + worker->current_func = work->func; worker->current_cwq = cwq; work_color = get_work_color(work); @@ -2186,7 +2207,7 @@ __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. @@ -2198,7 +2219,8 @@ __acquires(&gcwq->lock) if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { 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), f); + current->comm, preempt_count(), task_pid_nr(current), + worker->current_func); debug_show_held_locks(current); dump_stack(); } @@ -2212,6 +2234,7 @@ __acquires(&gcwq->lock) /* we're done with it, release */ hash_del(&worker->hentry); worker->current_work = NULL; + worker->current_func = NULL; worker->current_cwq = NULL; cwq_dec_nr_in_flight(cwq, work_color); } |
