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Fix taskq dynamic spawning

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Currently taskq_dispatch() will spawn new task with a condition that the caller
is also a member of the taskq. However, under this condition, it will still
cause deadlock where a task on tq1 is waiting another thread, who is trying to
dispatch a task on tq1. So this patch removes the check.

For example when you do:
zfs send pp/fs0@001 | zfs recv pp/fs0_copy

This will easily deadlock before this patch.

Also, move the seq_task check from taskq_thread_spawn() to taskq_thread()
because it's not used by the caller from taskq_dispatch().

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #496
This commit is contained in:
tuxoko 2015-11-06 15:00:55 -08:00 committed by Brian Behlendorf
parent 3e7e6f34d0
commit f5f2b87df0
1 changed files with 11 additions and 14 deletions
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25
module/spl/spl-taskq.c
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@ -538,7 +538,7 @@ 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);
static int taskq_thread_spawn(taskq_t *tq);
taskqid_t
taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
@ -587,9 +587,8 @@ 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);
if (tq->tq_nactive == tq->tq_nthreads)
(void) taskq_thread_spawn(tq);
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
return (rc);
@ -635,9 +634,8 @@ 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);
if (tq->tq_nactive == tq->tq_nthreads)
(void) taskq_thread_spawn(tq);
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
return (rc);
}
@ -683,9 +681,8 @@ 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);
if (tq->tq_nactive == tq->tq_nthreads)
(void) taskq_thread_spawn(tq);
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
}
EXPORT_SYMBOL(taskq_dispatch_ent);
@ -756,15 +753,14 @@ taskq_thread_spawn_task(void *arg)
* which is also a dynamic taskq cannot be safely used for this.
*/
static int
taskq_thread_spawn(taskq_t *tq, int seq_tasks)
taskq_thread_spawn(taskq_t *tq)
{
int spawning = 0;
if (!(tq->tq_flags & TASKQ_DYNAMIC))
return (0);
if ((seq_tasks > spl_taskq_thread_sequential) &&
(tq->tq_nthreads + tq->tq_nspawn < tq->tq_maxthreads) &&
if ((tq->tq_nthreads + tq->tq_nspawn < tq->tq_maxthreads) &&
(tq->tq_flags & TASKQ_ACTIVE)) {
spawning = (++tq->tq_nspawn);
taskq_dispatch(dynamic_taskq, taskq_thread_spawn_task,
@ -898,7 +894,8 @@ taskq_thread(void *args)
}
/* Spawn additional taskq threads if required. */
if (taskq_thread_spawn(tq, ++seq_tasks))
if ((++seq_tasks) > spl_taskq_thread_sequential &&
taskq_thread_spawn(tq))
seq_tasks = 0;
tqt->tqt_id = 0;