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Create a new thread during recursive taskq dispatch if necessary

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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 <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #472
This commit is contained in:
Tim Chase 2015-08-27 11:13:20 -05:00 committed by Brian Behlendorf
parent 801b56090b
commit a64e55752f
1 changed files with 28 additions and 3 deletions
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31
module/spl/spl-taskq.c
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@ -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);