Revert "Create a new thread during recursive taskq dispatch if necessary"

This reverts commit 076821e due to a locking issue uncovered in
subsequent testing.  An ASSERT is hit due to tq->tq_nspawn being
updated outside the lock.  The patch will need to be reworked.

VERIFY3(0 == tq->tq_nspawn) failed (0 == -1)

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #472

diff --git a/module/spl/spl-taskq.c b/module/spl/spl-taskq.c
index 2202aced78b8c30a8ee79b53ef6c8f7879948101..7a756af37aed97ea9e10d48e677e926e05436f24 100644 (file)
--- a/module/spl/spl-taskq.c
+++ b/module/spl/spl-taskq.c
@@ -53,7 +53,6 @@ EXPORT_SYMBOL(system_taskq);
 /* Private dedicated taskq for creating new taskq threads on demand. */
 static taskq_t *dynamic_taskq;
 static taskq_thread_t *taskq_thread_create(taskq_t *);
-static int taskq_thread_spawn(taskq_t *tq, int seq_tasks);
 
 static int
 task_km_flags(uint_t flags)
@@ -534,7 +533,6 @@ taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
 {
        taskq_ent_t *t;
        taskqid_t rc = 0;
-       boolean_t threadlimit = B_FALSE;
 
        ASSERT(tq);
        ASSERT(func);
@@ -576,13 +574,7 @@ taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
 
        wake_up(&tq->tq_work_waitq);
 out:
-       threadlimit = (tq->tq_nactive == tq->tq_nthreads);
        spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
-
-       /* Spawn additional taskq threads if required. */
-       if (threadlimit && taskq_member(tq, current))
-               (void) taskq_thread_spawn(tq, spl_taskq_thread_sequential + 1);
-
        return (rc);
 }
 EXPORT_SYMBOL(taskq_dispatch);
@@ -593,7 +585,6 @@ taskq_dispatch_delay(taskq_t *tq, task_func_t func, void *arg,
 {
        taskqid_t rc = 0;
        taskq_ent_t *t;
-       boolean_t threadlimit = B_FALSE;
 
        ASSERT(tq);
        ASSERT(func);
@@ -626,13 +617,7 @@ taskq_dispatch_delay(taskq_t *tq, task_func_t func, void *arg,
 
        spin_unlock(&t->tqent_lock);
 out:
-       threadlimit = (tq->tq_nactive == tq->tq_nthreads);
        spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
-
-       /* Spawn additional taskq threads if required. */
-       if (threadlimit && taskq_member(tq, current))
-               (void) taskq_thread_spawn(tq, spl_taskq_thread_sequential + 1);
-
        return (rc);
 }
 EXPORT_SYMBOL(taskq_dispatch_delay);
@@ -641,8 +626,6 @@ void
 taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
    taskq_ent_t *t)
 {
-       boolean_t threadlimit = B_FALSE;
-
        ASSERT(tq);
        ASSERT(func);
 
@@ -678,12 +661,7 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
 
        wake_up(&tq->tq_work_waitq);
 out:
-       threadlimit = (tq->tq_nactive == tq->tq_nthreads);
        spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
-
-       /* Spawn additional taskq threads if required. */
-       if (threadlimit && taskq_member(tq, current))
-               (void) taskq_thread_spawn(tq, spl_taskq_thread_sequential + 1);
 }
 EXPORT_SYMBOL(taskq_dispatch_ent);