New an improved taskq implementation for the SPL. It allows a

configurable number of threads like the Solaris version and almost
all of the options are supported.  Unfortunately, it appears to have
made absolutely no difference to our performance numbers.  I need
to keep looking for where we are bottle necking.



git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@93 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c

5 files changed, 484 insertions, 139 deletions

diff --git a/include/sys/condvar.h b/include/sys/condvar.h
index fd845d9c1..2878b68a8 100644
--- a/include/sys/condvar.h
+++ b/include/sys/condvar.h
@@ -28,6 +28,7 @@ typedef enum { CV_DEFAULT=0, CV_DRIVER } kcv_type_t;
 static __inline__ void
 cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
 {
+	ENTRY;
 	ASSERT(cvp);
 	ASSERT(type == CV_DEFAULT);
 	ASSERT(arg == NULL);
@@ -44,11 +45,14 @@ cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
 		if (cvp->cv_name)
 		        strcpy(cvp->cv_name, name);
 	}
+
+	EXIT;
 }
 
 static __inline__ void
 cv_destroy(kcondvar_t *cvp)
 {
+	ENTRY;
 	ASSERT(cvp);
 	ASSERT(cvp->cv_magic == CV_MAGIC);
 	spin_lock(&cvp->cv_lock);
@@ -60,12 +64,14 @@ cv_destroy(kcondvar_t *cvp)
 
 	memset(cvp, CV_POISON, sizeof(*cvp));
 	spin_unlock(&cvp->cv_lock);
+	EXIT;
 }
 
 static __inline__ void
 cv_wait(kcondvar_t *cvp, kmutex_t *mtx)
 {
 	DEFINE_WAIT(wait);
+	ENTRY;
 
 	ASSERT(cvp);
         ASSERT(mtx);
@@ -93,6 +99,7 @@ cv_wait(kcondvar_t *cvp, kmutex_t *mtx)
 
 	atomic_dec(&cvp->cv_waiters);
 	finish_wait(&cvp->cv_event, &wait);
+	EXIT;
 }
 
 /* 'expire_time' argument is an absolute wall clock time in jiffies.
@@ -103,6 +110,7 @@ cv_timedwait(kcondvar_t *cvp, kmutex_t *mtx, clock_t expire_time)
 {
 	DEFINE_WAIT(wait);
 	clock_t time_left;
+	ENTRY;
 
 	ASSERT(cvp);
         ASSERT(mtx);
@@ -120,7 +128,7 @@ cv_timedwait(kcondvar_t *cvp, kmutex_t *mtx, clock_t expire_time)
 	/* XXX - Does not handle jiffie wrap properly */
 	time_left = expire_time - jiffies;
 	if (time_left <= 0)
-		return -1;
+		RETURN(-1);
 
 	prepare_to_wait_exclusive(&cvp->cv_event, &wait,
 				  TASK_UNINTERRUPTIBLE);
@@ -136,12 +144,13 @@ cv_timedwait(kcondvar_t *cvp, kmutex_t *mtx, clock_t expire_time)
 	atomic_dec(&cvp->cv_waiters);
 	finish_wait(&cvp->cv_event, &wait);
 
-	return (time_left > 0 ? time_left : -1);
+	RETURN(time_left > 0 ? time_left : -1);
 }
 
 static __inline__ void
 cv_signal(kcondvar_t *cvp)
 {
+	ENTRY;
 	ASSERT(cvp);
 	ASSERT(cvp->cv_magic == CV_MAGIC);
 
@@ -151,6 +160,8 @@ cv_signal(kcondvar_t *cvp)
 	 * the wait queue to ensure we don't race waking up processes. */
 	if (atomic_read(&cvp->cv_waiters) > 0)
 		wake_up(&cvp->cv_event);
+
+	EXIT;
 }
 
 static __inline__ void
@@ -158,10 +169,13 @@ cv_broadcast(kcondvar_t *cvp)
 {
 	ASSERT(cvp);
 	ASSERT(cvp->cv_magic == CV_MAGIC);
+	ENTRY;
 
 	/* Wake_up_all() will wake up all waiters even those which
 	 * have the WQ_FLAG_EXCLUSIVE flag set. */
 	if (atomic_read(&cvp->cv_waiters) > 0)
 		wake_up_all(&cvp->cv_event);
+
+	EXIT;
 }
 #endif /* _SPL_CONDVAR_H */
diff --git a/include/sys/mutex.h b/include/sys/mutex.h
index d7036b566..045842d72 100644
--- a/include/sys/mutex.h
+++ b/include/sys/mutex.h
@@ -36,6 +36,7 @@ typedef struct {
 static __inline__ void
 mutex_init(kmutex_t *mp, char *name, int type, void *ibc)
 {
+	ENTRY;
 	ASSERT(mp);
 	ASSERT(ibc == NULL);		/* XXX - Spin mutexes not needed */
 	ASSERT(type == MUTEX_DEFAULT);	/* XXX - Only default type supported */
@@ -51,12 +52,14 @@ mutex_init(kmutex_t *mp, char *name, int type, void *ibc)
 		if (mp->km_name)
 			strcpy(mp->km_name, name);
 	}
+	EXIT;
 }
 
 #undef mutex_destroy
 static __inline__ void
 mutex_destroy(kmutex_t *mp)
 {
+	ENTRY;
 	ASSERT(mp);
 	ASSERT(mp->km_magic == KM_MAGIC);
 	spin_lock(&mp->km_lock);
@@ -66,11 +69,13 @@ mutex_destroy(kmutex_t *mp)
 
 	memset(mp, KM_POISON, sizeof(*mp));
 	spin_unlock(&mp->km_lock);
+	EXIT;
 }
 
 static __inline__ void
 mutex_enter(kmutex_t *mp)
 {
+	ENTRY;
 	ASSERT(mp);
 	ASSERT(mp->km_magic == KM_MAGIC);
 	spin_lock(&mp->km_lock);
@@ -91,6 +96,7 @@ mutex_enter(kmutex_t *mp)
 	ASSERT(mp->km_owner == NULL);
 	mp->km_owner = current;
 	spin_unlock(&mp->km_lock);
+	EXIT;
 }
 
 /* Return 1 if we acquired the mutex, else zero.  */
@@ -98,6 +104,7 @@ static __inline__ int
 mutex_tryenter(kmutex_t *mp)
 {
 	int rc;
+	ENTRY;
 
 	ASSERT(mp);
 	ASSERT(mp->km_magic == KM_MAGIC);
@@ -118,14 +125,16 @@ mutex_tryenter(kmutex_t *mp)
 		ASSERT(mp->km_owner == NULL);
 		mp->km_owner = current;
 		spin_unlock(&mp->km_lock);
-		return 1;
+		RETURN(1);
 	}
-	return 0;
+
+	RETURN(0);
 }
 
 static __inline__ void
 mutex_exit(kmutex_t *mp)
 {
+	ENTRY;
 	ASSERT(mp);
 	ASSERT(mp->km_magic == KM_MAGIC);
 	spin_lock(&mp->km_lock);
@@ -134,6 +143,7 @@ mutex_exit(kmutex_t *mp)
 	mp->km_owner = NULL;
 	spin_unlock(&mp->km_lock);
 	up(&mp->km_sem);
+	EXIT;
 }
 
 /* Return 1 if mutex is held by current process, else zero.  */
@@ -141,6 +151,7 @@ static __inline__ int
 mutex_owned(kmutex_t *mp)
 {
 	int rc;
+	ENTRY;
 
 	ASSERT(mp);
 	ASSERT(mp->km_magic == KM_MAGIC);
@@ -148,7 +159,7 @@ mutex_owned(kmutex_t *mp)
 	rc = (mp->km_owner == current);
 	spin_unlock(&mp->km_lock);
 
-	return rc;
+	RETURN(rc);
 }
 
 /* Return owner if mutex is owned, else NULL.  */
@@ -156,6 +167,7 @@ static __inline__ kthread_t *
 mutex_owner(kmutex_t *mp)
 {
 	kthread_t *thr;
+	ENTRY;
 
 	ASSERT(mp);
 	ASSERT(mp->km_magic == KM_MAGIC);
@@ -163,7 +175,7 @@ mutex_owner(kmutex_t *mp)
 	thr = mp->km_owner;
 	spin_unlock(&mp->km_lock);
 
-	return thr;
+	RETURN(thr);
 }
 
 #ifdef	__cplusplus
diff --git a/include/sys/taskq.h b/include/sys/taskq.h
index 14ba33280..ae8fbdb7b 100644
--- a/include/sys/taskq.h
+++ b/include/sys/taskq.h
@@ -5,82 +5,75 @@
 extern "C" {
 #endif
 
-/*
- * Task Queues - As of linux 2.6.x task queues have been replaced by a
- * similar construct called work queues.  The big difference on the linux
- * side is that functions called from work queues run in process context
- * and not interrupt context.
- *
- * One nice feature of Solaris which does not exist in linux work
- * queues in the notion of a dynamic work queue.  Rather than implementing
- * this in the shim layer I'm hardcoding one-thread per work queue.
- *
- * XXX - This may end up being a significant performance penalty which
- * forces us to implement dynamic workqueues.  Which is all very doable
- * with a little effort.
- */
 #include <linux/module.h>
-#include <linux/workqueue.h>
 #include <linux/gfp.h>
 #include <linux/slab.h>
 #include <linux/interrupt.h>
+#include <linux/kthread.h>
 #include <sys/types.h>
+#include <sys/kmem.h>
 
-#undef DEBUG_TASKQ_UNIMPLEMENTED
+#define TASKQ_NAMELEN           31
 
-#define TASKQ_NAMELEN   31
-#define taskq_t                         workq_t
+#define TASKQ_PREPOPULATE       0x00000001
+#define TASKQ_CPR_SAFE          0x00000002
+#define TASKQ_DYNAMIC           0x00000004
 
-typedef struct workqueue_struct workq_t;
 typedef unsigned long taskqid_t;
-typedef void (*task_func_t)(void *);
-
-/*
- * Public flags for taskq_create(): bit range 0-15
- */
-#define TASKQ_PREPOPULATE       0x0000  /* XXX - Workqueues fully populate */
-#define TASKQ_CPR_SAFE          0x0000  /* XXX - No analog */
-#define TASKQ_DYNAMIC           0x0000  /* XXX - Worksqueues not dynamic */
+typedef void (task_func_t)(void *);
 
 /*
  * Flags for taskq_dispatch. TQ_SLEEP/TQ_NOSLEEP should be same as
- * KM_SLEEP/KM_NOSLEEP.
+ * KM_SLEEP/KM_NOSLEEP.  TQ_NOQUEUE/TQ_NOALLOC are set particularly
+ * large so as not to conflict with already used GFP_* defines.
  */
-#define TQ_SLEEP                0x00    /* XXX - Workqueues don't support    */
-#define TQ_NOSLEEP              0x00    /*       these sorts of flags.  They */
-#define TQ_NOQUEUE              0x00    /*       always run in application   */
-#define TQ_NOALLOC              0x00    /*       context and can sleep.      */
-
-
-#ifdef DEBUG_TASKQ_UNIMPLEMENTED
-static __inline__ void taskq_init(void) {
-#error "taskq_init() not implemented"
-}
-
-static __inline__ taskq_t *
-taskq_create_instance(const char *, int, int, pri_t, int, int, uint_t) {
-#error "taskq_create_instance() not implemented"
-}
-
-extern void     nulltask(void *);
-extern void     taskq_suspend(taskq_t *);
-extern int      taskq_suspended(taskq_t *);
-extern void     taskq_resume(taskq_t *);
-
-#endif /* DEBUG_TASKQ_UNIMPLEMENTED */
+#define TQ_SLEEP                KM_SLEEP
+#define TQ_NOSLEEP              KM_NOSLEEP
+#define TQ_NOQUEUE              0x01000000
+#define TQ_NOALLOC              0x02000000
+#define TQ_NEW                  0x04000000
+#define TQ_ACTIVE               0x80000000
+
+typedef struct task {
+	spinlock_t              t_lock;
+	struct list_head        t_list;
+	taskqid_t               t_id;
+        task_func_t             *t_func;
+        void                    *t_arg;
+} task_t;
+
+typedef struct taskq {
+        spinlock_t              tq_lock;       /* protects taskq_t */
+        struct task_struct      **tq_threads;  /* thread pointers */
+	const char              *tq_name;      /* taskq name */
+        int                     tq_nactive;    /* # of active threads */
+        int                     tq_nthreads;   /* # of total threads */
+	int                     tq_pri;        /* priority */
+        int                     tq_minalloc;   /* min task_t pool size */
+        int                     tq_maxalloc;   /* max task_t pool size */
+	int                     tq_nalloc;     /* cur task_t pool size */
+        uint_t                  tq_flags;      /* flags */
+	taskqid_t               tq_next_id;    /* next pend/work id */
+	taskqid_t               tq_lowest_id;  /* lowest pend/work id */
+	struct list_head        tq_free_list;  /* free task_t's */
+	struct list_head        tq_work_list;  /* work task_t's */
+	struct list_head        tq_pend_list;  /* pending task_t's */
+	wait_queue_head_t       tq_work_waitq; /* new work waitq */
+	wait_queue_head_t       tq_wait_waitq; /* wait waitq */
+} taskq_t;
 
 extern taskqid_t __taskq_dispatch(taskq_t *, task_func_t, void *, uint_t);
 extern taskq_t *__taskq_create(const char *, int, pri_t, int, int, uint_t);
 extern void __taskq_destroy(taskq_t *);
 extern void __taskq_wait(taskq_t *);
-
-#define taskq_create(name, thr, pri, min, max, flags) \
-	__taskq_create(name, thr, pri, min, max, flags)
-#define taskq_dispatch(tq, func, priv, flags)         \
-	__taskq_dispatch(tq, (task_func_t)func, priv, flags)
-#define taskq_destroy(tq)                             __taskq_destroy(tq)
-#define taskq_wait(tq)                                __taskq_wait(tq)
-#define taskq_member(tq, kthr)                        1 /* XXX -Just be true */
+extern int __taskq_member(taskq_t *, void *);
+
+#define taskq_member(tq, t)                __taskq_member(tq, t)
+#define taskq_wait_id(tq, id)              __taskq_wait_id(tq, id)
+#define taskq_wait(tq)                     __taskq_wait(tq)
+#define taskq_dispatch(tq, f, p, fl)       __taskq_dispatch(tq, f, p, fl)
+#define taskq_create(n, th, p, mi, ma, fl) __taskq_create(n, th, p, mi, ma, fl)
+#define taskq_destroy(tq)                  __taskq_destroy(tq)
 
 #ifdef  __cplusplus
 }
diff --git a/modules/spl/spl-taskq.c b/modules/spl/spl-taskq.c
index d26b40db8..ad9be695b 100644
--- a/modules/spl/spl-taskq.c
+++ b/modules/spl/spl-taskq.c
@@ -6,109 +6,427 @@
 
 #define DEBUG_SUBSYSTEM S_TASKQ
 
-/*
- * Task queue interface
- *
- * The taskq_work_wrapper functions are used to manage the work_structs
- * which must be submitted to linux.  The shim layer allocates a wrapper
- * structure for all items which contains a pointer to itself as well as
- * the real work to be performed.  When the work item run the generic
- * handle is called which calls the real work function and then using
- * the self pointer frees the work_struct.
+/* NOTE: Must be called with tq->tq_lock held, returns a list_t which
+ * is not attached to the free, work, or pending taskq lists.
  */
-typedef struct taskq_work_wrapper {
-        struct work_struct tww_work;
-        task_func_t        tww_func;
-        void *             tww_priv;
-} taskq_work_wrapper_t;
+static task_t *
+task_alloc(taskq_t *tq, uint_t flags)
+{
+        task_t *t;
+        int count = 0;
+        ENTRY;
+
+        ASSERT(tq);
+        ASSERT(flags & (TQ_SLEEP | TQ_NOSLEEP));               /* One set */
+        ASSERT(!((flags & TQ_SLEEP) && (flags & TQ_NOSLEEP))); /* Not both */
+	ASSERT(spin_is_locked(&tq->tq_lock));
+retry:
+        /* Aquire task_t's from free list if available */
+        if (!list_empty(&tq->tq_free_list) && !(flags & TQ_NEW)) {
+                t = list_entry(tq->tq_free_list.next, task_t, t_list);
+	        list_del_init(&t->t_list);
+		RETURN(t);
+        }
+
+        /* Free list is empty and memory allocs are prohibited */
+        if (flags & TQ_NOALLOC)
+                RETURN(NULL);
+
+        /* Hit maximum task_t pool size */
+        if (tq->tq_nalloc >= tq->tq_maxalloc) {
+                if (flags & TQ_NOSLEEP)
+                        RETURN(NULL);
+
+                /* Sleep periodically polling the free list for an available
+                 * task_t.  If a full second passes and we have not found
+                 * one gives up and return a NULL to the caller. */
+                if (flags & TQ_SLEEP) {
+                        spin_unlock_irq(&tq->tq_lock);
+                        schedule_timeout(HZ / 100);
+                        spin_lock_irq(&tq->tq_lock);
+                        if (count < 100)
+                                GOTO(retry, count++);
+
+                        RETURN(NULL);
+                }
+
+                /* Unreachable, TQ_SLEEP xor TQ_NOSLEEP */
+                SBUG();
+        }
+
+	spin_unlock_irq(&tq->tq_lock);
+        t = kmem_alloc(sizeof(task_t), flags & (TQ_SLEEP | TQ_NOSLEEP));
+        spin_lock_irq(&tq->tq_lock);
+
+	if (t) {
+		spin_lock_init(&t->t_lock);
+                INIT_LIST_HEAD(&t->t_list);
+		t->t_id = 0;
+		t->t_func = NULL;
+		t->t_arg = NULL;
+		tq->tq_nalloc++;
+	}
+
+        RETURN(t);
+}
+
+/* NOTE: Must be called with tq->tq_lock held, expectes the task_t
+ * to already be removed from the free, work, or pending taskq lists.
+ */
+static void
+task_free(taskq_t *tq, task_t *t)
+{
+        ENTRY;
+
+        ASSERT(tq);
+        ASSERT(t);
+	ASSERT(spin_is_locked(&tq->tq_lock));
+	ASSERT(list_empty(&t->t_list));
+
+        kmem_free(t, sizeof(task_t));
+        tq->tq_nalloc--;
 
+	EXIT;
+}
+
+/* NOTE: Must be called with tq->tq_lock held, either destroyes the
+ * task_t if too many exist or moves it to the free list for later use.
+ */
 static void
-taskq_work_handler(void *priv)
+task_done(taskq_t *tq, task_t *t)
 {
-        taskq_work_wrapper_t *tww = priv;
+	ENTRY;
+	ASSERT(tq);
+	ASSERT(t);
+	ASSERT(spin_is_locked(&tq->tq_lock));
+
+	list_del_init(&t->t_list);
 
-        ASSERT(tww);
-        ASSERT(tww->tww_func);
+        if (tq->tq_nalloc <= tq->tq_minalloc) {
+		t->t_id = 0;
+		t->t_func = NULL;
+		t->t_arg = NULL;
+                list_add(&t->t_list, &tq->tq_free_list);
+	} else {
+		task_free(tq, t);
+	}
 
-        /* Call the real function and free the wrapper */
-        tww->tww_func(tww->tww_priv);
-        kfree(tww);
+        EXIT;
 }
 
-/* XXX - All flags currently ignored */
-taskqid_t
-__taskq_dispatch(taskq_t *tq, task_func_t func, void *priv, uint_t flags)
+/* Taskqid's are handed out in a monotonically increasing fashion per
+ * taskq_t.  We don't handle taskqid wrapping yet, but fortuntely it isi
+ * a 64-bit value so this is probably never going to happen.  The lowest
+ * pending taskqid is stored in the taskq_t to make it easy for any
+ * taskq_wait()'ers to know if the tasks they're waiting for have
+ * completed.  Unfortunately, tq_task_lowest is kept up to date is
+ * a pretty brain dead way, something more clever should be done.
+ */
+static int
+taskq_wait_check(taskq_t *tq, taskqid_t id)
+{
+	RETURN(tq->tq_lowest_id >= id);
+}
+
+/* Expected to wait for all previously scheduled tasks to complete.  We do
+ * not need to wait for tasked scheduled after this call to complete.  In
+ * otherwords we do not need to drain the entire taskq. */
+void
+__taskq_wait_id(taskq_t *tq, taskqid_t id)
 {
-        struct workqueue_struct *wq = tq;
-        taskq_work_wrapper_t *tww;
-        int rc;
 	ENTRY;
+	ASSERT(tq);
+
+	wait_event(tq->tq_wait_waitq, taskq_wait_check(tq, id));
+
+	EXIT;
+}
+EXPORT_SYMBOL(__taskq_wait_id);
+
+void
+__taskq_wait(taskq_t *tq)
+{
+	taskqid_t id;
+	ENTRY;
+	ASSERT(tq);
+
+	spin_lock_irq(&tq->tq_lock);
+	id = tq->tq_next_id;
+	spin_unlock_irq(&tq->tq_lock);
+
+	__taskq_wait_id(tq, id);
+
+	EXIT;
+
+}
+EXPORT_SYMBOL(__taskq_wait);
+
+int
+__taskq_member(taskq_t *tq, void *t)
+{
+        int i;
+        ENTRY;
+
+	ASSERT(tq);
+        ASSERT(t);
+
+        for (i = 0; i < tq->tq_nthreads; i++)
+                if (tq->tq_threads[i] == (struct task_struct *)t)
+                        RETURN(1);
+
+        RETURN(0);
+}
+EXPORT_SYMBOL(__taskq_member);
+
+taskqid_t
+__taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
+{
+        task_t *t;
+	taskqid_t rc = 0;
+        ENTRY;
 
         ASSERT(tq);
         ASSERT(func);
+        if (unlikely(in_atomic() && (flags & TQ_SLEEP))) {
+		CERROR("May schedule while atomic: %s/0x%08x/%d\n",
+                       current->comm, preempt_count(), current->pid);
+		SBUG();
+	}
 
-	/* Use GFP_ATOMIC since this may be called in interrupt context */
-        tww = (taskq_work_wrapper_t *)kmalloc(sizeof(*tww), GFP_ATOMIC);
-        if (!tww)
-                RETURN((taskqid_t)0);
+        spin_lock_irq(&tq->tq_lock);
 
-        INIT_WORK(&(tww->tww_work), taskq_work_handler, tww);
-        tww->tww_func = func;
-        tww->tww_priv = priv;
+	/* Taskq being destroyed and all tasks drained */
+	if (!(tq->tq_flags & TQ_ACTIVE))
+		GOTO(out, rc = 0);
 
-        rc = queue_work(wq, &(tww->tww_work));
-        if (!rc) {
-                kfree(tww);
-                RETURN((taskqid_t)0);
-        }
+	/* Do not queue the task unless there is idle thread for it */
+	ASSERT(tq->tq_nactive <= tq->tq_nthreads);
+	if ((flags & TQ_NOQUEUE) && (tq->tq_nactive == tq->tq_nthreads))
+		GOTO(out, rc = 0);
+
+        if ((t = task_alloc(tq, flags)) == NULL)
+		GOTO(out, rc = 0);
 
-        RETURN((taskqid_t)wq);
+
+	spin_lock(&t->t_lock);
+	list_add(&t->t_list, &tq->tq_pend_list);
+	t->t_id = rc = tq->tq_next_id;
+	tq->tq_next_id++;
+        t->t_func = func;
+        t->t_arg = arg;
+	spin_unlock(&t->t_lock);
+
+	wake_up(&tq->tq_work_waitq);
+out:
+	spin_unlock_irq(&tq->tq_lock);
+	RETURN(rc);
 }
 EXPORT_SYMBOL(__taskq_dispatch);
 
-/* XXX - We must fully implement dynamic workqueues since they make a
- *       significant impact in terms of performance.  For now I've made
- *       a trivial compromise.  If you ask for one thread you get one
- *       thread, if you ask for more than that you get one per core.
- *       It's unclear if you ever really need/want more than one per-core
- *       anyway.  More analysis is required.
- *
- * name  - Workqueue names are limited to 10 chars
- * pri   - Ignore priority
- * min   - Ignored until this is a dynamic thread pool
- * max   - Ignored until this is a dynamic thread pool
- * flags - Ignored until this is a dynamic thread_pool
- */
+/* NOTE: Must be called with tq->tq_lock held */
+static taskqid_t
+taskq_lowest_id(taskq_t *tq)
+{
+	taskqid_t lowest_id = ~0;
+        task_t *t;
+	ENTRY;
+
+	ASSERT(tq);
+	ASSERT(spin_is_locked(&tq->tq_lock));
+
+	list_for_each_entry(t, &tq->tq_pend_list, t_list)
+		if (t->t_id < lowest_id)
+			lowest_id = t->t_id;
+
+	list_for_each_entry(t, &tq->tq_work_list, t_list)
+		if (t->t_id < lowest_id)
+			lowest_id = t->t_id;
+
+	RETURN(lowest_id);
+}
+
+static int
+taskq_thread(void *args)
+{
+        DECLARE_WAITQUEUE(wait, current);
+        sigset_t blocked;
+	taskqid_t id;
+        taskq_t *tq = args;
+        task_t *t;
+	ENTRY;
+
+        ASSERT(tq);
+        current->flags |= PF_NOFREEZE;
+
+        sigfillset(&blocked);
+        sigprocmask(SIG_BLOCK, &blocked, NULL);
+        flush_signals(current);
+
+        spin_lock_irq(&tq->tq_lock);
+        tq->tq_nthreads++;
+        wake_up(&tq->tq_wait_waitq);
+        set_current_state(TASK_INTERRUPTIBLE);
+
+        while (!kthread_should_stop()) {
+
+		add_wait_queue(&tq->tq_work_waitq, &wait);
+		if (list_empty(&tq->tq_pend_list)) {
+	                spin_unlock_irq(&tq->tq_lock);
+			schedule();
+	                spin_lock_irq(&tq->tq_lock);
+		} else {
+			__set_current_state(TASK_RUNNING);
+		}
+
+		remove_wait_queue(&tq->tq_work_waitq, &wait);
+                if (!list_empty(&tq->tq_pend_list)) {
+                        t = list_entry(tq->tq_pend_list.next, task_t, t_list);
+                        list_del_init(&t->t_list);
+			list_add(&t->t_list, &tq->tq_work_list);
+                        tq->tq_nactive++;
+			spin_unlock_irq(&tq->tq_lock);
+
+			/* Perform the requested task */
+                        t->t_func(t->t_arg);
+
+			spin_lock_irq(&tq->tq_lock);
+                        tq->tq_nactive--;
+			id = t->t_id;
+                        task_done(tq, t);
+
+			/* Update the lowest remaining taskqid yet to run */
+			if (tq->tq_lowest_id == id) {
+				tq->tq_lowest_id = taskq_lowest_id(tq);
+				ASSERT(tq->tq_lowest_id > id);
+			}
+
+                        wake_up_all(&tq->tq_wait_waitq);
+		}
+
+		set_current_state(TASK_INTERRUPTIBLE);
+
+        }
+
+	__set_current_state(TASK_RUNNING);
+        tq->tq_nthreads--;
+        spin_unlock_irq(&tq->tq_lock);
+
+	RETURN(0);
+}
+
 taskq_t *
 __taskq_create(const char *name, int nthreads, pri_t pri,
                int minalloc, int maxalloc, uint_t flags)
 {
-	taskq_t *tq;
-	ENTRY;
+        taskq_t *tq;
+        struct task_struct *t;
+        int rc = 0, i, j = 0;
+        ENTRY;
+
+        ASSERT(name != NULL);
+        ASSERT(pri <= maxclsyspri);
+        ASSERT(minalloc >= 0);
+        ASSERT(maxalloc <= INT_MAX);
+        ASSERT(!(flags & (TASKQ_CPR_SAFE | TASKQ_DYNAMIC))); /* Unsupported */
+
+        tq = kmem_alloc(sizeof(*tq), KM_SLEEP);
+        if (tq == NULL)
+                RETURN(NULL);
+
+        tq->tq_threads = kmem_alloc(nthreads * sizeof(t), KM_SLEEP);
+        if (tq->tq_threads == NULL) {
+                kmem_free(tq, sizeof(*tq));
+                RETURN(NULL);
+        }
+
+        spin_lock_init(&tq->tq_lock);
+	spin_lock_irq(&tq->tq_lock);
+        tq->tq_name      = name;
+        tq->tq_nactive   = 0;
+	tq->tq_nthreads  = 0;
+        tq->tq_pri       = pri;
+        tq->tq_minalloc  = minalloc;
+        tq->tq_maxalloc  = maxalloc;
+	tq->tq_nalloc    = 0;
+        tq->tq_flags     = (flags | TQ_ACTIVE);
+	tq->tq_next_id   = 1;
+	tq->tq_lowest_id = 1;
+        INIT_LIST_HEAD(&tq->tq_free_list);
+        INIT_LIST_HEAD(&tq->tq_work_list);
+        INIT_LIST_HEAD(&tq->tq_pend_list);
+        init_waitqueue_head(&tq->tq_work_waitq);
+        init_waitqueue_head(&tq->tq_wait_waitq);
+
+        if (flags & TASKQ_PREPOPULATE)
+                for (i = 0; i < minalloc; i++)
+                        task_done(tq, task_alloc(tq, TQ_SLEEP | TQ_NEW));
 
-	if (nthreads == 1)
-		tq = create_singlethread_workqueue(name);
-	else
-		tq = create_workqueue(name);
+	spin_unlock_irq(&tq->tq_lock);
 
-	return tq;
+        for (i = 0; i < nthreads; i++) {
+                t = kthread_create(taskq_thread, tq, "%s/%d", name, i);
+                if (t) {
+                        tq->tq_threads[i] = t;
+                        kthread_bind(t, i % num_online_cpus());
+                        set_user_nice(t, PRIO_TO_NICE(pri));
+                        wake_up_process(t);
+			j++;
+                } else {
+                        tq->tq_threads[i] = NULL;
+                        rc = 1;
+                }
+        }
+
+        /* Wait for all threads to be started before potential destroy */
+	wait_event(tq->tq_wait_waitq, tq->tq_nthreads == j);
+
+        if (rc) {
+                __taskq_destroy(tq);
+                tq = NULL;
+        }
+
+        RETURN(tq);
 }
 EXPORT_SYMBOL(__taskq_create);
 
 void
 __taskq_destroy(taskq_t *tq)
 {
+	task_t *t;
+	int i, nthreads;
 	ENTRY;
-	destroy_workqueue(tq);
-	EXIT;
-}
-EXPORT_SYMBOL(__taskq_destroy);
 
-void
-__taskq_wait(taskq_t *tq)
-{
-	ENTRY;
-	flush_workqueue(tq);
+	ASSERT(tq);
+        spin_lock_irq(&tq->tq_lock);
+        tq->tq_flags &= ~TQ_ACTIVE;
+	spin_unlock_irq(&tq->tq_lock);
+
+	/* TQ_ACTIVE cleared prevents new tasks being added to pending */
+        __taskq_wait(tq);
+
+	nthreads = tq->tq_nthreads;
+	for (i = 0; i < nthreads; i++)
+		if (tq->tq_threads[i])
+			kthread_stop(tq->tq_threads[i]);
+
+        spin_lock_irq(&tq->tq_lock);
+
+        while (!list_empty(&tq->tq_free_list)) {
+		t = list_entry(tq->tq_free_list.next, task_t, t_list);
+	        list_del_init(&t->t_list);
+                task_free(tq, t);
+        }
+
+        ASSERT(tq->tq_nthreads == 0);
+        ASSERT(tq->tq_nalloc == 0);
+        ASSERT(list_empty(&tq->tq_free_list));
+        ASSERT(list_empty(&tq->tq_work_list));
+        ASSERT(list_empty(&tq->tq_pend_list));
+
+        spin_unlock_irq(&tq->tq_lock);
+        kmem_free(tq->tq_threads, nthreads * sizeof(task_t *));
+        kmem_free(tq, sizeof(taskq_t));
+
 	EXIT;
 }
-EXPORT_SYMBOL(__taskq_wait);
+EXPORT_SYMBOL(__taskq_destroy);
diff --git a/modules/splat/splat-taskq.c b/modules/splat/splat-taskq.c
index 6effc4cab..b4d07c95d 100644
--- a/modules/splat/splat-taskq.c
+++ b/modules/splat/splat-taskq.c
@@ -43,7 +43,8 @@ splat_taskq_test1(struct file *file, void *arg)
 
 	splat_vprint(file, SPLAT_TASKQ_TEST1_NAME, "Taskq '%s' creating\n",
 	           SPLAT_TASKQ_TEST1_NAME);
-	if ((tq = taskq_create(SPLAT_TASKQ_TEST1_NAME, 1, 0, 0, 0, 0)) == NULL) {
+	if ((tq = taskq_create(SPLAT_TASKQ_TEST1_NAME, 1, maxclsyspri,
+			       50, INT_MAX, TASKQ_PREPOPULATE)) == NULL) {
 		splat_vprint(file, SPLAT_TASKQ_TEST1_NAME,
 		           "Taskq '%s' create failed\n",
 		           SPLAT_TASKQ_TEST1_NAME);
@@ -58,7 +59,8 @@ splat_taskq_test1(struct file *file, void *arg)
 	splat_vprint(file, SPLAT_TASKQ_TEST1_NAME,
 	           "Taskq '%s' function '%s' dispatching\n",
 	           tq_arg.name, sym2str(splat_taskq_test1_func));
-	if ((id = taskq_dispatch(tq, splat_taskq_test1_func, &tq_arg, 0)) == 0) {
+	if ((id = taskq_dispatch(tq, splat_taskq_test1_func,
+				 &tq_arg, TQ_SLEEP)) == 0) {
 		splat_vprint(file, SPLAT_TASKQ_TEST1_NAME,
 		           "Taskq '%s' function '%s' dispatch failed\n",
 		           tq_arg.name, sym2str(splat_taskq_test1_func));
@@ -109,6 +111,8 @@ splat_taskq_test2_func2(void *arg)
 }
 
 #define TEST2_TASKQS                    8
+#define TEST2_THREADS_PER_TASKQ         4
+
 static int
 splat_taskq_test2(struct file *file, void *arg) {
 	taskq_t *tq[TEST2_TASKQS] = { NULL };
@@ -121,7 +125,9 @@ splat_taskq_test2(struct file *file, void *arg) {
 		splat_vprint(file, SPLAT_TASKQ_TEST2_NAME, "Taskq '%s/%d' "
 		           "creating\n", SPLAT_TASKQ_TEST2_NAME, i);
 		if ((tq[i] = taskq_create(SPLAT_TASKQ_TEST2_NAME,
-			                  1, 0, 0, 0, 0)) == NULL) {
+			                  TEST2_THREADS_PER_TASKQ,
+					  maxclsyspri, 50, INT_MAX,
+					  TASKQ_PREPOPULATE)) == NULL) {
 			splat_vprint(file, SPLAT_TASKQ_TEST2_NAME,
 			           "Taskq '%s/%d' create failed\n",
 				   SPLAT_TASKQ_TEST2_NAME, i);
@@ -139,7 +145,8 @@ splat_taskq_test2(struct file *file, void *arg) {
 			   tq_args[i].name, tq_args[i].id,
 		           sym2str(splat_taskq_test2_func1));
 		if ((id = taskq_dispatch(
-		     tq[i], splat_taskq_test2_func1, &tq_args[i], 0)) == 0) {
+		     tq[i], splat_taskq_test2_func1,
+		     &tq_args[i], TQ_SLEEP)) == 0) {
 			splat_vprint(file, SPLAT_TASKQ_TEST2_NAME,
 			           "Taskq '%s/%d' function '%s' dispatch "
 			           "failed\n", tq_args[i].name, tq_args[i].id,
@@ -153,7 +160,8 @@ splat_taskq_test2(struct file *file, void *arg) {
 			   tq_args[i].name, tq_args[i].id,
 		           sym2str(splat_taskq_test2_func2));
 		if ((id = taskq_dispatch(
-		     tq[i], splat_taskq_test2_func2, &tq_args[i], 0)) == 0) {
+		     tq[i], splat_taskq_test2_func2,
+		     &tq_args[i], TQ_SLEEP)) == 0) {
 			splat_vprint(file, SPLAT_TASKQ_TEST2_NAME,
 			           "Taskq '%s/%d' function '%s' dispatch failed\n",
 			           tq_args[i].name, tq_args[i].id,