From a64e55752f4e88dcb544f2480100dcd6f6be3277 Mon Sep 17 00:00:00 2001 From: Tim Chase Date: Thu, 27 Aug 2015 11:13:20 -0500 Subject: [PATCH] Create a new thread during recursive taskq dispatch if necessary When dynamic taskq is enabled and all threads for a taskq are occupied, a recursive dispatch can cause a deadlock if calling thread depends on the recursively-dispatched thread for its return condition. This patch attempts to create a new thread for recursive dispatch when none are available. Signed-off-by: Tim Chase Signed-off-by: Brian Behlendorf Closes #472 --- module/spl/spl-taskq.c | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/module/spl/spl-taskq.c b/module/spl/spl-taskq.c index 7a756af..82e71a3 100644 --- a/module/spl/spl-taskq.c +++ b/module/spl/spl-taskq.c @@ -448,8 +448,8 @@ taskq_wait(taskq_t *tq) } EXPORT_SYMBOL(taskq_wait); -int -taskq_member(taskq_t *tq, void *t) +static int +taskq_member_impl(taskq_t *tq, void *t) { struct list_head *l; taskq_thread_t *tqt; @@ -457,8 +457,8 @@ taskq_member(taskq_t *tq, void *t) ASSERT(tq); ASSERT(t); + ASSERT(spin_is_locked(&tq->tq_lock)); - spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); list_for_each(l, &tq->tq_thread_list) { tqt = list_entry(l, taskq_thread_t, tqt_thread_list); if (tqt->tqt_thread == (struct task_struct *)t) { @@ -466,6 +466,16 @@ taskq_member(taskq_t *tq, void *t) break; } } + return (found); +} + +int +taskq_member(taskq_t *tq, void *t) +{ + int found; + + spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); + found = taskq_member_impl(tq, t); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); return (found); @@ -528,6 +538,8 @@ taskq_cancel_id(taskq_t *tq, taskqid_t id) } EXPORT_SYMBOL(taskq_cancel_id); +static int taskq_thread_spawn(taskq_t *tq, int seq_tasks); + taskqid_t taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags) { @@ -574,6 +586,11 @@ taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags) wake_up(&tq->tq_work_waitq); out: + /* Spawn additional taskq threads if required. */ + if (tq->tq_nactive == tq->tq_nthreads && + taskq_member_impl(tq, current)) + (void) taskq_thread_spawn(tq, spl_taskq_thread_sequential + 1); + spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); return (rc); } @@ -617,6 +634,10 @@ taskq_dispatch_delay(taskq_t *tq, task_func_t func, void *arg, spin_unlock(&t->tqent_lock); out: + /* Spawn additional taskq threads if required. */ + if (tq->tq_nactive == tq->tq_nthreads && + taskq_member_impl(tq, current)) + (void) taskq_thread_spawn(tq, spl_taskq_thread_sequential + 1); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); return (rc); } @@ -661,6 +682,10 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags, wake_up(&tq->tq_work_waitq); out: + /* Spawn additional taskq threads if required. */ + if (tq->tq_nactive == tq->tq_nthreads && + taskq_member_impl(tq, current)) + (void) taskq_thread_spawn(tq, spl_taskq_thread_sequential + 1); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); } EXPORT_SYMBOL(taskq_dispatch_ent); -- 2.39.2