Name: Extra debugging stuff for hotplug CPU.
Author: Rusty Russell
Status: Booted on 2.6.0-test6-bk1
Depends: Hotcpu/hotcpu-i386.patch.gz

D: For chasing down the sleeping tasks bug.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .16933-linux-2.6.0-test7-bk4/kernel/workqueue.c .16933-linux-2.6.0-test7-bk4.updated/kernel/workqueue.c
--- .16933-linux-2.6.0-test7-bk4/kernel/workqueue.c	2003-10-13 08:55:21.000000000 +1000
+++ .16933-linux-2.6.0-test7-bk4.updated/kernel/workqueue.c	2003-10-13 08:55:22.000000000 +1000
@@ -348,6 +367,26 @@ int current_is_keventd(void)
 	return 0;
 }
 
+void show_workqueues(void)
+{
+	struct workqueue_struct *wq;
+	unsigned int cpu;
+	extern void show_blk(void);
+
+	show_blk();
+	list_for_each_entry(wq, &workqueues, list) {
+		for_each_cpu(cpu)
+			printk("%s: %u: %s %p %i %li %li\n",
+			       wq->name, cpu,
+			       list_empty(&wq->cpu_wq[cpu].worklist)
+			       ? "EMPTY" : "SOME",
+			       wq->cpu_wq[cpu].worker,
+			       waitqueue_active(&wq->cpu_wq[cpu].work_done),
+			       wq->cpu_wq[cpu].insert_sequence,
+			       wq->cpu_wq[cpu].remove_sequence);
+	}
+}
+
 #ifdef CONFIG_HOTPLUG_CPU
 /* Take the work from this (downed) CPU. */
 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .11453-2.6.0-test6-bk7-hotcpu-i386.pre/drivers/block/ll_rw_blk.c .11453-2.6.0-test6-bk7-hotcpu-i386/drivers/block/ll_rw_blk.c
--- .11453-2.6.0-test6-bk7-hotcpu-i386.pre/drivers/block/ll_rw_blk.c	2003-10-06 06:14:00.000000000 +1000
+++ .11453-2.6.0-test6-bk7-hotcpu-i386/drivers/block/ll_rw_blk.c	2003-10-06 16:17:51.000000000 +1000
@@ -99,6 +99,8 @@ static void clear_queue_congested(reques
 	enum bdi_state bit;
 	wait_queue_head_t *wqh = &congestion_wqh[rw];
 
+	printk("clear_queue_congested %p %i on %u\n",
+	       q, rw, smp_processor_id());
 	bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
 	clear_bit(bit, &q->backing_dev_info.state);
 	if (waitqueue_active(wqh))
@@ -1786,6 +1788,10 @@ void blk_put_request(struct request *req
 	}
 }
 
+#include <linux/percpu.h>
+#include <asm/atomic.h>
+static DEFINE_PER_CPU(local_t, blk_congestion_count);
+
 /**
  * blk_congestion_wait - wait for a queue to become uncongested
  * @rw: READ or WRITE
@@ -1800,10 +1806,38 @@ void blk_congestion_wait(int rw, long ti
 	DEFINE_WAIT(wait);
 	wait_queue_head_t *wqh = &congestion_wqh[rw];
 
+	cpu_local_inc(blk_congestion_count);
 	blk_run_queues();
 	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 	io_schedule_timeout(timeout);
 	finish_wait(wqh, &wait);
+	cpu_local_dec(blk_congestion_count);
+}
+
+
+void show_blk(void)
+{
+	unsigned int cpu;
+	wait_queue_t *w;
+	wait_queue_head_t *wqh;
+
+	for_each_cpu(cpu)
+		printk("blk_congestion_count for %u: %li\n", 
+		       cpu, local_read(&per_cpu(blk_congestion_count, cpu)));
+
+	wqh = &congestion_wqh[READ];
+	spin_lock(&wqh->lock);
+	printk("Waiting for read congestion:\n");
+	list_for_each_entry(w, &wqh->task_list, task_list)
+		printk("%s: %u\n", w->task->comm, w->task->pid);
+	spin_unlock(&wqh->lock);
+
+	wqh = &congestion_wqh[WRITE];
+	spin_lock(&wqh->lock);
+	printk("Waiting for write congestion:\n");
+	list_for_each_entry(w, &wqh->task_list, task_list)
+		printk("%s: %u\n", w->task->comm, w->task->pid);
+	spin_unlock(&wqh->lock);
 }
 
 /*
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .11453-2.6.0-test6-bk7-hotcpu-i386.pre/drivers/char/sysrq.c .11453-2.6.0-test6-bk7-hotcpu-i386/drivers/char/sysrq.c
--- .11453-2.6.0-test6-bk7-hotcpu-i386.pre/drivers/char/sysrq.c	2003-09-29 10:25:26.000000000 +1000
+++ .11453-2.6.0-test6-bk7-hotcpu-i386/drivers/char/sysrq.c	2003-10-06 16:17:51.000000000 +1000
@@ -214,6 +214,19 @@ static struct sysrq_key_op sysrq_kill_op
 	.action_msg	= "Kill All Tasks",
 };
 
+static void sysrq_handle_workqueues(int key, struct pt_regs *pt_regs,
+				    struct tty_struct *tty) 
+{
+	extern void show_workqueues(void);
+
+	show_workqueues();
+}
+static struct sysrq_key_op sysrq_workqueueus_op = {
+	.handler	= sysrq_handle_workqueues,
+	.help_msg	= "Workq",
+	.action_msg	= "Showing Workqueues",
+};
+
 /* END SIGNAL SYSRQ HANDLERS BLOCK */
 
 
@@ -264,7 +277,7 @@ static struct sysrq_key_op *sysrq_key_ta
 /* t */	&sysrq_showstate_op,
 /* u */	&sysrq_mountro_op,
 /* v */	NULL, /* May be assigned at init time by SMP VOYAGER */
-/* w */	NULL,
+/* w */	&sysrq_workqueueus_op,
 /* x */	NULL,
 /* y */	NULL,
 /* z */	NULL