diff options
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index a3aea405d773..86b6e43d41b5 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -226,6 +226,8 @@ struct worker_pool { /* L: hash of busy workers */ struct worker *manager; /* L: purely informational */ + /* L: last worker woken by kick_pool() */ + struct worker *last_woken_worker; struct list_head workers; /* A: attached workers */ struct ida worker_ida; /* worker IDs for task name */ @@ -1318,6 +1320,9 @@ static bool kick_pool_pick(struct worker_pool *pool, struct task_struct **wakep) } } #endif + /* Track the last idle worker woken, used for stall diagnostics. */ + pool->last_woken_worker = worker; + *wakep = p; return true; } @@ -2976,6 +2981,13 @@ static void set_worker_dying(struct worker *worker, struct list_head *list) pool->nr_workers--; pool->nr_idle--; + /* + * Clear last_woken_worker if it points to this worker, so that + * show_cpu_pool_busy_workers() cannot dereference a freed worker. + */ + if (pool->last_woken_worker == worker) + pool->last_woken_worker = NULL; + worker->flags |= WORKER_DIE; list_move(&worker->entry, list); @@ -7740,13 +7752,25 @@ static void show_pool_no_running_worker(struct worker_pool *pool) idle_cpu(pool->cpu) ? "idle" : "busy", pool->nr_workers, pool->nr_idle); pr_info("The pool might have trouble waking an idle worker.\n"); + /* + * last_woken_worker and its task are valid here: set_worker_dying() + * clears it under pool->lock before setting WORKER_DIE, so if + * last_woken_worker is non-NULL the kthread has not yet exited and + * worker->task is still alive. + */ + if (pool->last_woken_worker) { + pr_info("Backtrace of last woken worker:\n"); + sched_show_task(pool->last_woken_worker->task); + } else { + pr_info("Last woken worker empty\n"); + } printk_deferred_exit(); } /* * Show running workers that might prevent the processing of pending work items. * If no running worker is found, the pool may be stuck waiting for an idle - * worker to be woken, so report the pool state. + * worker to be woken, so report the pool state and the last woken worker. */ static void show_cpu_pool_busy_workers(struct worker_pool *pool) { @@ -7781,7 +7805,8 @@ static void show_cpu_pool_busy_workers(struct worker_pool *pool) /* * If no running worker was found, the pool is likely stuck. Print pool - * state. + * state and the backtrace of the last woken worker, which is the prime + * suspect for the stall. */ if (!found_running) show_pool_no_running_worker(pool); |