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https://github.com/torvalds/linux
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workqueue changes for v6.4-rc1
Mostly changes from Petr to improve warning and error reporting. Workqueue now reports more of the relevant failures with better context which should help debugging. -----BEGIN PGP SIGNATURE----- iIQEABYIACwWIQTfIjM1kS57o3GsC/uxYfJx3gVYGQUCZErbOg4cdGpAa2VybmVs Lm9yZwAKCRCxYfJx3gVYGfipAP9BXrUBI99uZL7XjSEe6rLWa0STODyWh67ikR+0 nUO22QEA+ttt5ecLZyopYB18Le06VBBW7J5cs0Cg83bCBTGb4wE= =gHbc -----END PGP SIGNATURE----- Merge tag 'wq-for-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq Pull workqueue updates from Tejun Heo: "Mostly changes from Petr to improve warning and error reporting. Workqueue now reports more of the relevant failures with better context which should help debugging" * tag 'wq-for-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: workqueue: Introduce show_freezable_workqueues workqueue: Print backtraces from CPUs with hung CPU bound workqueues workqueue: Warn when a rescuer could not be created workqueue: Interrupted create_worker() is not a repeated event workqueue: Warn when a new worker could not be created workqueue: Fix hung time report of worker pools workqueue: Simplify a pr_warn() call in wq_select_unbound_cpu() MAINTAINERS: Add workqueue_internal.h to the WORKQUEUE entry
This commit is contained in:
commit
cd546fa325
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@ -22743,6 +22743,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git
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F: Documentation/core-api/workqueue.rst
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F: include/linux/workqueue.h
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F: kernel/workqueue.c
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F: kernel/workqueue_internal.h
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WWAN DRIVERS
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M: Loic Poulain <loic.poulain@linaro.org>
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@ -472,6 +472,7 @@ extern unsigned int work_busy(struct work_struct *work);
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extern __printf(1, 2) void set_worker_desc(const char *fmt, ...);
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extern void print_worker_info(const char *log_lvl, struct task_struct *task);
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extern void show_all_workqueues(void);
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extern void show_freezable_workqueues(void);
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extern void show_one_workqueue(struct workqueue_struct *wq);
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extern void wq_worker_comm(char *buf, size_t size, struct task_struct *task);
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@ -93,7 +93,7 @@ static int try_to_freeze_tasks(bool user_only)
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todo - wq_busy, wq_busy);
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if (wq_busy)
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show_all_workqueues();
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show_freezable_workqueues();
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if (!wakeup || pm_debug_messages_on) {
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read_lock(&tasklist_lock);
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@ -49,6 +49,7 @@
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#include <linux/moduleparam.h>
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#include <linux/uaccess.h>
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#include <linux/sched/isolation.h>
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#include <linux/sched/debug.h>
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#include <linux/nmi.h>
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#include <linux/kvm_para.h>
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@ -141,6 +142,8 @@ enum {
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* WR: wq->mutex protected for writes. RCU protected for reads.
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*
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* MD: wq_mayday_lock protected.
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*
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* WD: Used internally by the watchdog.
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*/
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/* struct worker is defined in workqueue_internal.h */
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@ -153,6 +156,7 @@ struct worker_pool {
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unsigned int flags; /* X: flags */
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unsigned long watchdog_ts; /* L: watchdog timestamp */
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bool cpu_stall; /* WD: stalled cpu bound pool */
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/*
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* The counter is incremented in a process context on the associated CPU
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@ -1392,15 +1396,13 @@ static bool is_chained_work(struct workqueue_struct *wq)
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*/
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static int wq_select_unbound_cpu(int cpu)
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{
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static bool printed_dbg_warning;
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int new_cpu;
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if (likely(!wq_debug_force_rr_cpu)) {
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if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
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return cpu;
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} else if (!printed_dbg_warning) {
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pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
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printed_dbg_warning = true;
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} else {
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pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
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}
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if (cpumask_empty(wq_unbound_cpumask))
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@ -1938,12 +1940,17 @@ static struct worker *create_worker(struct worker_pool *pool)
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/* ID is needed to determine kthread name */
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id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
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if (id < 0)
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if (id < 0) {
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pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
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ERR_PTR(id));
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return NULL;
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}
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worker = alloc_worker(pool->node);
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if (!worker)
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if (!worker) {
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pr_err_once("workqueue: Failed to allocate a worker\n");
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goto fail;
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}
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worker->id = id;
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@ -1955,8 +1962,16 @@ static struct worker *create_worker(struct worker_pool *pool)
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worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
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"kworker/%s", id_buf);
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if (IS_ERR(worker->task))
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if (IS_ERR(worker->task)) {
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if (PTR_ERR(worker->task) == -EINTR) {
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pr_err("workqueue: Interrupted when creating a worker thread \"kworker/%s\"\n",
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id_buf);
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} else {
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pr_err_once("workqueue: Failed to create a worker thread: %pe",
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worker->task);
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}
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goto fail;
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}
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set_user_nice(worker->task, pool->attrs->nice);
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kthread_bind_mask(worker->task, pool->attrs->cpumask);
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@ -4380,13 +4395,18 @@ static int init_rescuer(struct workqueue_struct *wq)
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return 0;
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rescuer = alloc_worker(NUMA_NO_NODE);
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if (!rescuer)
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if (!rescuer) {
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pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
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wq->name);
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return -ENOMEM;
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}
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rescuer->rescue_wq = wq;
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rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
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if (IS_ERR(rescuer->task)) {
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ret = PTR_ERR(rescuer->task);
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pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
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wq->name, ERR_PTR(ret));
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kfree(rescuer);
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return ret;
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}
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@ -5002,10 +5022,16 @@ static void show_one_worker_pool(struct worker_pool *pool)
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struct worker *worker;
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bool first = true;
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unsigned long flags;
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unsigned long hung = 0;
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raw_spin_lock_irqsave(&pool->lock, flags);
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if (pool->nr_workers == pool->nr_idle)
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goto next_pool;
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/* How long the first pending work is waiting for a worker. */
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if (!list_empty(&pool->worklist))
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hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
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/*
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* Defer printing to avoid deadlocks in console drivers that
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* queue work while holding locks also taken in their write
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@ -5014,9 +5040,7 @@ static void show_one_worker_pool(struct worker_pool *pool)
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printk_deferred_enter();
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pr_info("pool %d:", pool->id);
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pr_cont_pool_info(pool);
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pr_cont(" hung=%us workers=%d",
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jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
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pool->nr_workers);
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pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
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if (pool->manager)
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pr_cont(" manager: %d",
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task_pid_nr(pool->manager->task));
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@ -5041,8 +5065,7 @@ static void show_one_worker_pool(struct worker_pool *pool)
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/**
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* show_all_workqueues - dump workqueue state
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*
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* Called from a sysrq handler or try_to_freeze_tasks() and prints out
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* all busy workqueues and pools.
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* Called from a sysrq handler and prints out all busy workqueues and pools.
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*/
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void show_all_workqueues(void)
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{
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@ -5063,6 +5086,29 @@ void show_all_workqueues(void)
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rcu_read_unlock();
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}
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/**
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* show_freezable_workqueues - dump freezable workqueue state
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*
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* Called from try_to_freeze_tasks() and prints out all freezable workqueues
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* still busy.
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*/
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void show_freezable_workqueues(void)
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{
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struct workqueue_struct *wq;
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rcu_read_lock();
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pr_info("Showing freezable workqueues that are still busy:\n");
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list_for_each_entry_rcu(wq, &workqueues, list) {
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if (!(wq->flags & WQ_FREEZABLE))
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continue;
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show_one_workqueue(wq);
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}
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rcu_read_unlock();
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}
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/* used to show worker information through /proc/PID/{comm,stat,status} */
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void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
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{
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@ -5962,6 +6008,57 @@ static struct timer_list wq_watchdog_timer;
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static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
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static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
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/*
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* Show workers that might prevent the processing of pending work items.
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* The only candidates are CPU-bound workers in the running state.
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* Pending work items should be handled by another idle worker
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* in all other situations.
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*/
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static void show_cpu_pool_hog(struct worker_pool *pool)
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{
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struct worker *worker;
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unsigned long flags;
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int bkt;
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raw_spin_lock_irqsave(&pool->lock, flags);
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hash_for_each(pool->busy_hash, bkt, worker, hentry) {
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if (task_is_running(worker->task)) {
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/*
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* Defer printing to avoid deadlocks in console
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* drivers that queue work while holding locks
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* also taken in their write paths.
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*/
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printk_deferred_enter();
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pr_info("pool %d:\n", pool->id);
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sched_show_task(worker->task);
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printk_deferred_exit();
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}
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}
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raw_spin_unlock_irqrestore(&pool->lock, flags);
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}
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static void show_cpu_pools_hogs(void)
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{
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struct worker_pool *pool;
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int pi;
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pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
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rcu_read_lock();
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for_each_pool(pool, pi) {
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if (pool->cpu_stall)
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show_cpu_pool_hog(pool);
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}
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rcu_read_unlock();
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}
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static void wq_watchdog_reset_touched(void)
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{
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int cpu;
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{
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unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
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bool lockup_detected = false;
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bool cpu_pool_stall = false;
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unsigned long now = jiffies;
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struct worker_pool *pool;
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int pi;
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for_each_pool(pool, pi) {
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unsigned long pool_ts, touched, ts;
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pool->cpu_stall = false;
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if (list_empty(&pool->worklist))
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continue;
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/* did we stall? */
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if (time_after(now, ts + thresh)) {
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lockup_detected = true;
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if (pool->cpu >= 0) {
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pool->cpu_stall = true;
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cpu_pool_stall = true;
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}
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pr_emerg("BUG: workqueue lockup - pool");
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pr_cont_pool_info(pool);
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pr_cont(" stuck for %us!\n",
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jiffies_to_msecs(now - pool_ts) / 1000);
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}
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}
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rcu_read_unlock();
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if (lockup_detected)
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show_all_workqueues();
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if (cpu_pool_stall)
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show_cpu_pools_hogs();
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wq_watchdog_reset_touched();
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mod_timer(&wq_watchdog_timer, jiffies + thresh);
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}
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