Subclass tq_lock to eliminate a lockdep warning
When taskq_dispatch() calls taskq_thread_spawn() to create a new thread for a taskq, linux lockdep warns of possible recursive locking. This is a false positive. One such call chain is as follows, when a taskq needs more threads: taskq_dispatch->taskq_thread_spawn->taskq_dispatch The initial taskq_dispatch() holds tq_lock on the taskq that needed more worker threads. The later call into taskq_dispatch() takes dynamic_taskq->tq_lock. Without subclassing, lockdep believes these could potentially be the same lock and complains. A similar case occurs when taskq_dispatch() then calls task_alloc(). This patch uses spin_lock_irqsave_nested() when taking tq_lock, with one of two new lock subclasses: subclass taskq TQ_LOCK_DYNAMIC dynamic_taskq TQ_LOCK_GENERAL any other Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #480
This commit is contained in:
Olaf Faaland
Brian Behlendorf
parent
628fc52137
commit
326172d854
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@ -55,6 +55,14 @@
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#define TQ_NEW 0x04000000
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#define TQ_FRONT 0x08000000
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/* spin_lock(lock) and spin_lock_nested(lock,0) are equivalent,
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* so TQ_LOCK_DYNAMIC must not evaluate to 0
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*/
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typedef enum tq_lock_role {
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TQ_LOCK_GENERAL = 0,
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TQ_LOCK_DYNAMIC = 1,
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} tq_lock_role_t;
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typedef unsigned long taskqid_t;
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typedef void (task_func_t)(void *);
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@ -81,6 +89,7 @@ typedef struct taskq {
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struct list_head tq_delay_list; /* delayed task_t's */
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wait_queue_head_t tq_work_waitq; /* new work waitq */
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wait_queue_head_t tq_wait_waitq; /* wait waitq */
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tq_lock_role_t tq_lock_class; /* class used when taking tq_lock */
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} taskq_t;
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typedef struct taskq_ent {
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@ -113,7 +113,8 @@ retry:
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*/
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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schedule_timeout(HZ / 100);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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if (count < 100) {
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count++;
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goto retry;
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@ -122,7 +123,8 @@ retry:
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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t = kmem_alloc(sizeof(taskq_ent_t), task_km_flags(flags));
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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if (t) {
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taskq_init_ent(t);
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@ -188,7 +190,8 @@ task_expire(unsigned long data)
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taskq_t *tq = t->tqent_taskq;
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struct list_head *l;
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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if (t->tqent_flags & TQENT_FLAG_CANCEL) {
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ASSERT(list_empty(&t->tqent_list));
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@ -379,7 +382,8 @@ taskq_wait_id_check(taskq_t *tq, taskqid_t id)
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int active = 0;
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int rc;
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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rc = (taskq_find(tq, id, &active) == NULL);
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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@ -402,7 +406,8 @@ taskq_wait_outstanding_check(taskq_t *tq, taskqid_t id)
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{
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int rc;
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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rc = (id < tq->tq_lowest_id);
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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@ -429,7 +434,8 @@ taskq_wait_check(taskq_t *tq)
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{
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int rc;
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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rc = (tq->tq_lowest_id == tq->tq_next_id);
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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@ -474,7 +480,8 @@ taskq_member(taskq_t *tq, void *t)
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{
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int found;
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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found = taskq_member_impl(tq, t);
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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@ -497,7 +504,8 @@ taskq_cancel_id(taskq_t *tq, taskqid_t id)
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ASSERT(tq);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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t = taskq_find(tq, id, &active);
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if (t && !active) {
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list_del_init(&t->tqent_list);
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@ -519,7 +527,8 @@ taskq_cancel_id(taskq_t *tq, taskqid_t id)
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if (timer_pending(&t->tqent_timer)) {
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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del_timer_sync(&t->tqent_timer);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock,
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tq->tq_lock_flags, tq->tq_lock_class);
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}
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if (!(t->tqent_flags & TQENT_FLAG_PREALLOC))
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@ -549,7 +558,8 @@ taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
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ASSERT(tq);
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ASSERT(func);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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/* Taskq being destroyed and all tasks drained */
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if (!(tq->tq_flags & TASKQ_ACTIVE))
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@ -605,7 +615,8 @@ taskq_dispatch_delay(taskq_t *tq, task_func_t func, void *arg,
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ASSERT(tq);
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ASSERT(func);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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/* Taskq being destroyed and all tasks drained */
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if (!(tq->tq_flags & TASKQ_ACTIVE))
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@ -648,7 +659,8 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
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ASSERT(tq);
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ASSERT(func);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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/* Taskq being destroyed and all tasks drained */
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if (!(tq->tq_flags & TASKQ_ACTIVE)) {
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@ -740,13 +752,14 @@ taskq_thread_spawn_task(void *arg)
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(void) taskq_thread_create(tq);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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tq->tq_nspawn--;
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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}
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/*
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* Spawn addition threads for dynamic taskqs (TASKQ_DYNMAIC) the current
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* Spawn addition threads for dynamic taskqs (TASKQ_DYNAMIC) the current
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* number of threads is insufficient to handle the pending tasks. These
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* new threads must be created by the dedicated dynamic_taskq to avoid
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* deadlocks between thread creation and memory reclaim. The system_taskq
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@ -810,6 +823,7 @@ taskq_thread(void *args)
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int seq_tasks = 0;
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ASSERT(tqt);
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ASSERT(tqt->tqt_tq);
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tq = tqt->tqt_tq;
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current->flags |= PF_NOFREEZE;
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@ -821,7 +835,8 @@ taskq_thread(void *args)
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sigprocmask(SIG_BLOCK, &blocked, NULL);
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flush_signals(current);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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/* Immediately exit if more threads than allowed were created. */
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if (tq->tq_nthreads >= tq->tq_maxthreads)
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@ -848,7 +863,8 @@ taskq_thread(void *args)
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schedule();
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seq_tasks = 0;
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock,
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tq->tq_lock_flags, tq->tq_lock_class);
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remove_wait_queue(&tq->tq_work_waitq, &wait);
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} else {
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__set_current_state(TASK_RUNNING);
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@ -877,7 +893,8 @@ taskq_thread(void *args)
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/* Perform the requested task */
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t->tqent_func(t->tqent_arg);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock,
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tq->tq_lock_flags, tq->tq_lock_class);
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tq->tq_nactive--;
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list_del_init(&tqt->tqt_active_list);
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tqt->tqt_task = NULL;
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@ -999,9 +1016,11 @@ taskq_create(const char *name, int nthreads, pri_t pri,
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INIT_LIST_HEAD(&tq->tq_delay_list);
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init_waitqueue_head(&tq->tq_work_waitq);
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init_waitqueue_head(&tq->tq_wait_waitq);
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tq->tq_lock_class = TQ_LOCK_GENERAL;
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if (flags & TASKQ_PREPOPULATE) {
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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for (i = 0; i < minalloc; i++)
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task_done(tq, task_alloc(tq, TQ_PUSHPAGE | TQ_NEW));
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@ -1040,7 +1059,8 @@ taskq_destroy(taskq_t *tq)
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taskq_ent_t *t;
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ASSERT(tq);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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tq->tq_flags &= ~TASKQ_ACTIVE;
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spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
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@ -1053,7 +1073,8 @@ taskq_destroy(taskq_t *tq)
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taskq_wait(tq);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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/*
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* Signal each thread to exit and block until it does. Each thread
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@ -1069,7 +1090,8 @@ taskq_destroy(taskq_t *tq)
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kthread_stop(thread);
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spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
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spin_lock_irqsave_nested(&tq->tq_lock, tq->tq_lock_flags,
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tq->tq_lock_class);
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}
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while (!list_empty(&tq->tq_free_list)) {
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@ -1113,6 +1135,12 @@ spl_taskq_init(void)
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return (1);
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}
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/* This is used to annotate tq_lock, so
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* taskq_dispatch -> taskq_thread_spawn -> taskq_dispatch
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* does not trigger a lockdep warning re: possible recursive locking
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*/
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dynamic_taskq->tq_lock_class = TQ_LOCK_DYNAMIC;
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return (0);
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}
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