From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Fri, 11 Jun 2010 21:53:23 +0000 (-0700)
Subject: Support TQ_FRONT flag used by taskq_dispatch()
X-Git-Tag: spl-0.5.0~46
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=eb12b3782c94113d2d40d2da22265dc4111a672b;p=spl

Support TQ_FRONT flag used by taskq_dispatch()

Allow taskq_dispatch() to insert work items at the head of the
queue instead of just the tail by passing the TQ_FRONT flag.
---

diff --git a/include/sys/taskq.h b/include/sys/taskq.h
index baa96ea..4e51d98 100644
--- a/include/sys/taskq.h
+++ b/include/sys/taskq.h
@@ -39,6 +39,7 @@
 #define TASKQ_CPR_SAFE          0x00000002
 #define TASKQ_DYNAMIC           0x00000004
 #define TASKQ_THREADS_CPU_PCT   0x00000008
+#define TASKQ_DC_BATCH          0x00000010
 
 typedef unsigned long taskqid_t;
 typedef void (task_func_t)(void *);
@@ -53,6 +54,7 @@ typedef void (task_func_t)(void *);
 #define TQ_NOQUEUE              0x01000000
 #define TQ_NOALLOC              0x02000000
 #define TQ_NEW                  0x04000000
+#define TQ_FRONT                0x08000000
 #define TQ_ACTIVE               0x80000000
 
 typedef struct taskq {
diff --git a/module/spl/spl-taskq.c b/module/spl/spl-taskq.c
index 805749a..fba3802 100644
--- a/module/spl/spl-taskq.c
+++ b/module/spl/spl-taskq.c
@@ -274,7 +274,13 @@ __taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
 		GOTO(out, rc = 0);
 
 	spin_lock(&t->t_lock);
-	list_add_tail(&t->t_list, &tq->tq_pend_list);
+
+	/* Queue to the head instead of the tail */
+	if (flags & TQ_FRONT)
+		list_add(&t->t_list, &tq->tq_pend_list);
+	else
+		list_add_tail(&t->t_list, &tq->tq_pend_list);
+
 	t->t_id = rc = tq->tq_next_id;
 	tq->tq_next_id++;
         t->t_func = func;