Provide kstat for taskqs

This patch provides 2 new kstats to display task queues:

  /proc/spl/taskqs-all - Display all task queues
  /proc/spl/taskqs - Display only "active" task queues

A task queue is considered to be "active" if it currently has active
(running) threads or if any of its pending, priority, delay or waitq
lists are not empty.

If the task queue has running threads, displays each thread function's
address (symbolically, if possibly) and its argument.

If the task queue has a non-empty list of pending, priority or delayed
task queue entries (taskq_ent_t), displays each entry's thread function
address and arguemnt.

If the task queue has any waiters, displays each waiting task's pid.

Note: This patch also updates some comments in taskq.h which referred to
"taskq_t" when they should have referred to "taskq_ent_t".

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #491

include/sys/taskq.h

@@ -32,6 +32,7 @@
 #include <linux/kthread.h>
 #include <sys/types.h>
 #include <sys/thread.h>
+#include <sys/rwlock.h>
 
 #define	TASKQ_NAMELEN		31
 
@@ -70,6 +71,7 @@ typedef void (task_func_t)(void *);
 typedef struct taskq {
 	spinlock_t		tq_lock;	/* protects taskq_t */
 	char			*tq_name;	/* taskq name */
+	int			tq_instance;	/* instance of tq_name */
 	struct list_head	tq_thread_list;	/* list of all threads */
 	struct list_head	tq_active_list;	/* list of active threads */
 	int			tq_nactive;	/* # of active threads */
@@ -77,16 +79,17 @@ typedef struct taskq {
 	int			tq_nspawn;	/* # of threads being spawned */
 	int			tq_maxthreads;	/* # of threads maximum */
 	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 */
+	int			tq_minalloc;	/* min taskq_ent_t pool size */
+	int			tq_maxalloc;	/* max taskq_ent_t pool size */
+	int			tq_nalloc;	/* cur taskq_ent_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_pend_list;	/* pending task_t's */
-	struct list_head	tq_prio_list;	/* priority pending task_t's */
-	struct list_head	tq_delay_list;	/* delayed task_t's */
+	struct list_head	tq_free_list;	/* free taskq_ent_t's */
+	struct list_head	tq_pend_list;	/* pending taskq_ent_t's */
+	struct list_head	tq_prio_list;	/* priority pending taskq_ent_t's */
+	struct list_head	tq_delay_list;	/* delayed taskq_ent_t's */
+	struct list_head	tq_taskqs;	/* all taskq_t's */
 	wait_queue_head_t	tq_work_waitq;	/* new work waitq */
 	wait_queue_head_t	tq_wait_waitq;	/* wait waitq */
 	tq_lock_role_t		tq_lock_class;	/* class when taking tq_lock */
@@ -120,6 +123,10 @@ typedef struct taskq_thread {
 /* Global system-wide dynamic task queue available for all consumers */
 extern taskq_t *system_taskq;
 
+/* List of all taskqs */
+extern struct list_head tq_list;
+extern struct rw_semaphore tq_list_sem;
+
 extern taskqid_t taskq_dispatch(taskq_t *, task_func_t, void *, uint_t);
 extern taskqid_t taskq_dispatch_delay(taskq_t *, task_func_t, void *,
     uint_t, clock_t);

module/spl/spl-proc.c

@@ -29,6 +29,7 @@
 #include <sys/kmem.h>
 #include <sys/kmem_cache.h>
 #include <sys/vmem.h>
+#include <sys/taskq.h>
 #include <linux/ctype.h>
 #include <linux/kmod.h>
 #include <linux/seq_file.h>
@@ -49,6 +50,8 @@ static struct ctl_table_header *spl_header = NULL;
 static struct proc_dir_entry *proc_spl = NULL;
 static struct proc_dir_entry *proc_spl_kmem = NULL;
 static struct proc_dir_entry *proc_spl_kmem_slab = NULL;
+static struct proc_dir_entry *proc_spl_taskq_all = NULL;
+static struct proc_dir_entry *proc_spl_taskq = NULL;
 struct proc_dir_entry *proc_spl_kstat = NULL;
 
 static int
@@ -215,6 +218,176 @@ proc_dohostid(struct ctl_table *table, int write,
         return (rc);
 }
 
+static void
+taskq_seq_show_headers(struct seq_file *f)
+{
+	seq_printf(f, "%-25s %5s %5s %5s %5s %5s %5s %12s %5s %10s\n",
+	    "taskq", "act", "nthr", "spwn", "maxt", "pri",
+	    "mina", "maxa", "cura", "flags");
+}
+
+/* indices into the lheads array below */
+#define	LHEAD_PEND	0
+#define LHEAD_PRIO	1
+#define LHEAD_DELAY	2
+#define LHEAD_WAIT	3
+#define LHEAD_ACTIVE	4
+#define LHEAD_SIZE	5
+
+static int
+taskq_seq_show_impl(struct seq_file *f, void *p, boolean_t allflag)
+{
+	taskq_t *tq = p;
+	taskq_thread_t *tqt;
+	wait_queue_t *wq;
+	struct task_struct *tsk;
+	taskq_ent_t *tqe;
+	char name[100];
+	struct list_head *lheads[LHEAD_SIZE], *lh;
+	static char *list_names[LHEAD_SIZE] =
+	    {"pend", "prio", "delay", "wait", "active" };
+	int i, j, have_lheads = 0;
+	unsigned long wflags, flags;
+
+	spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
+	spin_lock_irqsave(&tq->tq_wait_waitq.lock, wflags);
+
+	/* get the various lists and check whether they're empty */
+	lheads[LHEAD_PEND] = &tq->tq_pend_list;
+	lheads[LHEAD_PRIO] = &tq->tq_prio_list;
+	lheads[LHEAD_DELAY] = &tq->tq_delay_list;
+	lheads[LHEAD_WAIT] = &tq->tq_wait_waitq.task_list;
+	lheads[LHEAD_ACTIVE] = &tq->tq_active_list;
+
+	for (i = 0; i < LHEAD_SIZE; ++i) {
+		if (list_empty(lheads[i]))
+			lheads[i] = NULL;
+		else
+			++have_lheads;
+	}
+
+	/* early return in non-"all" mode if lists are all empty */
+	if (!allflag && !have_lheads) {
+		spin_unlock_irqrestore(&tq->tq_wait_waitq.lock, wflags);
+		spin_unlock_irqrestore(&tq->tq_lock, flags);
+		return (0);
+	}
+
+	/* unlock the waitq quickly */
+	if (!lheads[LHEAD_WAIT])
+		spin_unlock_irqrestore(&tq->tq_wait_waitq.lock, wflags);
+
+	/* show the base taskq contents */
+	snprintf(name, sizeof(name), "%s/%d", tq->tq_name, tq->tq_instance);
+	seq_printf(f, "%-25s ", name);
+	seq_printf(f, "%5d %5d %5d %5d %5d %5d %12d %5d %10x\n",
+	    tq->tq_nactive, tq->tq_nthreads, tq->tq_nspawn,
+	    tq->tq_maxthreads, tq->tq_pri, tq->tq_minalloc, tq->tq_maxalloc,
+	    tq->tq_nalloc, tq->tq_flags);
+
+	/* show the active list */
+	if (lheads[LHEAD_ACTIVE]) {
+		j = 0;
+		list_for_each_entry(tqt, &tq->tq_active_list, tqt_active_list) {
+			if (j == 0)
+				seq_printf(f, "\t%s:", list_names[LHEAD_ACTIVE]);
+			else if (j == 2) {
+				seq_printf(f, "\n\t       ");
+				j = 0;
+			}
+			seq_printf(f, " [%d]%pf(%ps)",
+			    tqt->tqt_thread->pid,
+			    tqt->tqt_task->tqent_func,
+			    tqt->tqt_task->tqent_arg);
+			++j;
+		}
+		seq_printf(f, "\n");
+	}
+
+	for (i = LHEAD_PEND; i <= LHEAD_WAIT; ++i)
+		if (lheads[i]) {
+			j = 0;
+			list_for_each(lh, lheads[i]) {
+				/* show the wait waitq list */
+				if (i == LHEAD_WAIT) {
+					wq = list_entry(lh, wait_queue_t, task_list);
+					if (j == 0)
+						seq_printf(f, "\t%s:",
+						    list_names[i]);
+					else if (j == 12) {
+						seq_printf(f, "\n\t     ");
+						j = 0;
+					}
+					tsk = wq->private;
+					seq_printf(f, " %d", tsk->pid);
+				/* pend, prio and delay lists */
+				} else {
+					tqe = list_entry(lh, taskq_ent_t,
+					    tqent_list);
+					if (j == 0)
+						seq_printf(f, "\t%s:",
+						    list_names[i]);
+					else if (j == 2) {
+						seq_printf(f, "\n\t     ");
+						j = 0;
+					}
+					seq_printf(f, " %pf(%ps)",
+					    tqe->tqent_func,
+					    tqe->tqent_arg);
+				}
+				++j;
+			}
+			seq_printf(f, "\n");
+		}
+	if (lheads[LHEAD_WAIT])
+		spin_unlock_irqrestore(&tq->tq_wait_waitq.lock, wflags);
+	spin_unlock_irqrestore(&tq->tq_lock, flags);
+
+	return (0);
+}
+
+static int
+taskq_all_seq_show(struct seq_file *f, void *p)
+{
+	return (taskq_seq_show_impl(f, p, B_TRUE));
+}
+
+static int
+taskq_seq_show(struct seq_file *f, void *p)
+{
+	return (taskq_seq_show_impl(f, p, B_FALSE));
+}
+
+static void *
+taskq_seq_start(struct seq_file *f, loff_t *pos)
+{
+	struct list_head *p;
+	loff_t n = *pos;
+
+	down_read(&tq_list_sem);
+	if (!n)
+		taskq_seq_show_headers(f);
+
+	p = tq_list.next;
+	while (n--) {
+		p = p->next;
+		if (p == &tq_list)
+		return (NULL);
+	}
+
+	return (list_entry(p, taskq_t, tq_taskqs));
+}
+
+static void *
+taskq_seq_next(struct seq_file *f, void *p, loff_t *pos)
+{
+	taskq_t *tq = p;
+
+	++*pos;
+	return ((tq->tq_taskqs.next == &tq_list) ?
+	       NULL : list_entry(tq->tq_taskqs.next, taskq_t, tq_taskqs));
+}
+
 static void
 slab_seq_show_headers(struct seq_file *f)
 {
@@ -325,6 +498,52 @@ static struct file_operations proc_slab_operations = {
         .release        = seq_release,
 };
 
+static void
+taskq_seq_stop(struct seq_file *f, void *v)
+{
+	up_read(&tq_list_sem);
+}
+
+static struct seq_operations taskq_all_seq_ops = {
+	.show  = taskq_all_seq_show,
+	.start = taskq_seq_start,
+	.next  = taskq_seq_next,
+	.stop  = taskq_seq_stop,
+};
+
+static struct seq_operations taskq_seq_ops = {
+	.show  = taskq_seq_show,
+	.start = taskq_seq_start,
+	.next  = taskq_seq_next,
+	.stop  = taskq_seq_stop,
+};
+
+static int
+proc_taskq_all_open(struct inode *inode, struct file *filp)
+{
+	return seq_open(filp, &taskq_all_seq_ops);
+}
+
+static int
+proc_taskq_open(struct inode *inode, struct file *filp)
+{
+	return seq_open(filp, &taskq_seq_ops);
+}
+
+static struct file_operations proc_taskq_all_operations = {
+	.open           = proc_taskq_all_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = seq_release,
+};
+
+static struct file_operations proc_taskq_operations = {
+	.open           = proc_taskq_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = seq_release,
+};
+
 static struct ctl_table spl_kmem_table[] = {
 #ifdef DEBUG_KMEM
         {
@@ -476,6 +695,20 @@ spl_proc_init(void)
 		goto out;
 	}
 
+	proc_spl_taskq_all = proc_create_data("taskq-all", 0444,
+		proc_spl, &proc_taskq_all_operations, NULL);
+	if (proc_spl_taskq_all == NULL) {
+		rc = -EUNATCH;
+		goto out;
+	}
+
+	proc_spl_taskq = proc_create_data("taskq", 0444,
+		proc_spl, &proc_taskq_operations, NULL);
+	if (proc_spl_taskq == NULL) {
+		rc = -EUNATCH;
+		goto out;
+	}
+
         proc_spl_kmem = proc_mkdir("kmem", proc_spl);
         if (proc_spl_kmem == NULL) {
                 rc = -EUNATCH;
@@ -499,6 +732,8 @@ out:
 		remove_proc_entry("kstat", proc_spl);
 	        remove_proc_entry("slab", proc_spl_kmem);
 		remove_proc_entry("kmem", proc_spl);
+		remove_proc_entry("taskq-all", proc_spl);
+		remove_proc_entry("taskq", proc_spl);
 		remove_proc_entry("spl", NULL);
 	        unregister_sysctl_table(spl_header);
 	}
@@ -512,6 +747,8 @@ spl_proc_fini(void)
 	remove_proc_entry("kstat", proc_spl);
         remove_proc_entry("slab", proc_spl_kmem);
 	remove_proc_entry("kmem", proc_spl);
+	remove_proc_entry("taskq-all", proc_spl);
+	remove_proc_entry("taskq", proc_spl);
 	remove_proc_entry("spl", NULL);
 
         ASSERT(spl_header != NULL);

module/spl/spl-taskq.c

@@ -54,6 +54,10 @@ EXPORT_SYMBOL(system_taskq);
 static taskq_t *dynamic_taskq;
 static taskq_thread_t *taskq_thread_create(taskq_t *);
 
+/* List of all taskqs */
+LIST_HEAD(tq_list);
+DECLARE_RWSEM(tq_list_sem);
+
 static int
 task_km_flags(uint_t flags)
 {
@@ -66,6 +70,23 @@ task_km_flags(uint_t flags)
 	return (KM_SLEEP);
 }
 
+/*
+ * taskq_find_by_name - Find the largest instance number of a named taskq.
+ */
+static int
+taskq_find_by_name(const char *name)
+{
+	struct list_head *tql;
+	taskq_t *tq;
+
+	list_for_each_prev(tql, &tq_list) {
+		tq = list_entry(tql, taskq_t, tq_taskqs);
+		if (strcmp(name, tq->tq_name) == 0)
+			return tq->tq_instance;
+	}
+	return (-1);
+}
+
 /*
  * 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.
@@ -1024,6 +1045,7 @@ taskq_create(const char *name, int nthreads, pri_t pri,
 	init_waitqueue_head(&tq->tq_work_waitq);
 	init_waitqueue_head(&tq->tq_wait_waitq);
 	tq->tq_lock_class = TQ_LOCK_GENERAL;
+	INIT_LIST_HEAD(&tq->tq_taskqs);
 
 	if (flags & TASKQ_PREPOPULATE) {
 		spin_lock_irqsave_nested(&tq->tq_lock, irqflags,
@@ -1053,6 +1075,11 @@ taskq_create(const char *name, int nthreads, pri_t pri,
 	if (rc) {
 		taskq_destroy(tq);
 		tq = NULL;
+	} else {
+		down_write(&tq_list_sem);
+		tq->tq_instance = taskq_find_by_name(name) + 1;
+		list_add_tail(&tq->tq_taskqs, &tq_list);
+		up_write(&tq_list_sem);
 	}
 
 	return (tq);
@@ -1081,6 +1108,11 @@ taskq_destroy(taskq_t *tq)
 
 	taskq_wait(tq);
 
+	/* remove taskq from global list used by the kstats */
+	down_write(&tq_list_sem);
+	list_del(&tq->tq_taskqs);
+	up_write(&tq_list_sem);
+
 	spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
 
 	/*