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authorTejun Heo <tj@kernel.org>2015-03-09 09:22:28 -0400
committerTejun Heo <tj@kernel.org>2015-03-09 09:22:28 -0400
commit3494fc30846dceb808de4cc02930ef347fabd21a (patch)
tree76e7e2e213e94bf6f371dfd518c793621c14b3f6 /kernel/workqueue.c
parent2607d7a6dba1e790aaacb14600ceffa3aa2f43e7 (diff)
downloadlinux-sh-3494fc30846dceb808de4cc02930ef347fabd21a.tar.gz
workqueue: dump workqueues on sysrq-t
Workqueues are used extensively throughout the kernel but sometimes it's difficult to debug stalls involving work items because visibility into its inner workings is fairly limited. Although sysrq-t task dump annotates each active worker task with the information on the work item being executed, it is challenging to find out which work items are pending or delayed on which queues and how pools are being managed. This patch implements show_workqueue_state() which dumps all busy workqueues and pools and is called from the sysrq-t handler. At the end of sysrq-t dump, something like the following is printed. Showing busy workqueues and worker pools: ... workqueue filler_wq: flags=0x0 pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 in-flight: 491:filler_workfn, 507:filler_workfn pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=2/256 in-flight: 501:filler_workfn pending: filler_workfn ... workqueue test_wq: flags=0x8 pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 in-flight: 510(RESCUER):test_workfn BAR(69) BAR(500) delayed: test_workfn1 BAR(492), test_workfn2 ... pool 0: cpus=0 node=0 flags=0x0 nice=0 workers=2 manager: 137 pool 2: cpus=1 node=0 flags=0x0 nice=0 workers=3 manager: 469 pool 3: cpus=1 node=0 flags=0x0 nice=-20 workers=2 idle: 16 pool 8: cpus=0-3 flags=0x4 nice=0 workers=2 manager: 62 The above shows that test_wq is executing test_workfn() on pid 510 which is the rescuer and also that there are two tasks 69 and 500 waiting for the work item to finish in flush_work(). As test_wq has max_active of 1, there are two work items for test_workfn1() and test_workfn2() which are delayed till the current work item is finished. In addition, pid 492 is flushing test_workfn1(). The work item for test_workfn() is being executed on pwq of pool 2 which is the normal priority per-cpu pool for CPU 1. The pool has three workers, two of which are executing filler_workfn() for filler_wq and the last one is assuming the manager role trying to create more workers. This extra workqueue state dump will hopefully help chasing down hangs involving workqueues. v3: cpulist_pr_cont() replaced with "%*pbl" printf formatting. v2: As suggested by Andrew, minor formatting change in pr_cont_work(), printk()'s replaced with pr_info()'s, and cpumask printing now uses cpulist_pr_cont(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> CC: Ingo Molnar <mingo@redhat.com>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r--kernel/workqueue.c160
1 files changed, 160 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 0c329a6f0c51..1ca0b1d54e70 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4457,6 +4457,166 @@ void print_worker_info(const char *log_lvl, struct task_struct *task)
}
}
+static void pr_cont_pool_info(struct worker_pool *pool)
+{
+ pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
+ if (pool->node != NUMA_NO_NODE)
+ pr_cont(" node=%d", pool->node);
+ pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
+}
+
+static void pr_cont_work(bool comma, struct work_struct *work)
+{
+ if (work->func == wq_barrier_func) {
+ struct wq_barrier *barr;
+
+ barr = container_of(work, struct wq_barrier, work);
+
+ pr_cont("%s BAR(%d)", comma ? "," : "",
+ task_pid_nr(barr->task));
+ } else {
+ pr_cont("%s %pf", comma ? "," : "", work->func);
+ }
+}
+
+static void show_pwq(struct pool_workqueue *pwq)
+{
+ struct worker_pool *pool = pwq->pool;
+ struct work_struct *work;
+ struct worker *worker;
+ bool has_in_flight = false, has_pending = false;
+ int bkt;
+
+ pr_info(" pwq %d:", pool->id);
+ pr_cont_pool_info(pool);
+
+ pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
+ !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
+
+ hash_for_each(pool->busy_hash, bkt, worker, hentry) {
+ if (worker->current_pwq == pwq) {
+ has_in_flight = true;
+ break;
+ }
+ }
+ if (has_in_flight) {
+ bool comma = false;
+
+ pr_info(" in-flight:");
+ hash_for_each(pool->busy_hash, bkt, worker, hentry) {
+ if (worker->current_pwq != pwq)
+ continue;
+
+ pr_cont("%s %d%s:%pf", comma ? "," : "",
+ task_pid_nr(worker->task),
+ worker == pwq->wq->rescuer ? "(RESCUER)" : "",
+ worker->current_func);
+ list_for_each_entry(work, &worker->scheduled, entry)
+ pr_cont_work(false, work);
+ comma = true;
+ }
+ pr_cont("\n");
+ }
+
+ list_for_each_entry(work, &pool->worklist, entry) {
+ if (get_work_pwq(work) == pwq) {
+ has_pending = true;
+ break;
+ }
+ }
+ if (has_pending) {
+ bool comma = false;
+
+ pr_info(" pending:");
+ list_for_each_entry(work, &pool->worklist, entry) {
+ if (get_work_pwq(work) != pwq)
+ continue;
+
+ pr_cont_work(comma, work);
+ comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
+ }
+ pr_cont("\n");
+ }
+
+ if (!list_empty(&pwq->delayed_works)) {
+ bool comma = false;
+
+ pr_info(" delayed:");
+ list_for_each_entry(work, &pwq->delayed_works, entry) {
+ pr_cont_work(comma, work);
+ comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
+ }
+ pr_cont("\n");
+ }
+}
+
+/**
+ * show_workqueue_state - dump workqueue state
+ *
+ * Called from a sysrq handler and prints out all busy workqueues and
+ * pools.
+ */
+void show_workqueue_state(void)
+{
+ struct workqueue_struct *wq;
+ struct worker_pool *pool;
+ unsigned long flags;
+ int pi;
+
+ rcu_read_lock_sched();
+
+ pr_info("Showing busy workqueues and worker pools:\n");
+
+ list_for_each_entry_rcu(wq, &workqueues, list) {
+ struct pool_workqueue *pwq;
+ bool idle = true;
+
+ for_each_pwq(pwq, wq) {
+ if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
+ idle = false;
+ break;
+ }
+ }
+ if (idle)
+ continue;
+
+ pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
+
+ for_each_pwq(pwq, wq) {
+ spin_lock_irqsave(&pwq->pool->lock, flags);
+ if (pwq->nr_active || !list_empty(&pwq->delayed_works))
+ show_pwq(pwq);
+ spin_unlock_irqrestore(&pwq->pool->lock, flags);
+ }
+ }
+
+ for_each_pool(pool, pi) {
+ struct worker *worker;
+ bool first = true;
+
+ spin_lock_irqsave(&pool->lock, flags);
+ if (pool->nr_workers == pool->nr_idle)
+ goto next_pool;
+
+ pr_info("pool %d:", pool->id);
+ pr_cont_pool_info(pool);
+ pr_cont(" workers=%d", pool->nr_workers);
+ if (pool->manager)
+ pr_cont(" manager: %d",
+ task_pid_nr(pool->manager->task));
+ list_for_each_entry(worker, &pool->idle_list, entry) {
+ pr_cont(" %s%d", first ? "idle: " : "",
+ task_pid_nr(worker->task));
+ first = false;
+ }
+ pr_cont("\n");
+ next_pool:
+ spin_unlock_irqrestore(&pool->lock, flags);
+ }
+
+ rcu_read_unlock_sched();
+}
+
/*
* CPU hotplug.
*