[PATCH 2.6.25-rc6] Add a "show workqueues" SYSRQ knob.

[Frank Mayhar <fmayhar@google.com>]

This patch adds a convenient function to show all workqueues using the
magic SYSRQ handling.  It uses the 'z' key to invoke the function as the
'w' key was already gone.

I've found this very useful in debugging; hopefully others will find it
as useful.

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index de60e1e..733d625 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -243,6 +243,18 @@ static struct sysrq_key_op sysrq_showmem_op = {
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };
 
+static void sysrq_handle_showwq(int key, struct pt_regs *pt_regs,
+				   struct tty_struct *tty)
+{
+	show_workqueues();
+}
+static struct sysrq_key_op sysrq_showwq_op = {
+	.handler	= sysrq_handle_showwq,
+	.help_msg	= "showworkqueueZ",
+	.action_msg	= "Show Workqueues",
+	.enable_mask	= SYSRQ_ENABLE_DUMP,
+};
+
 /*
  * Signal sysrq helper function.  Sends a signal to all user processes.
  */
@@ -358,7 +370,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
 	/* x: May be registered on ppc/powerpc for xmon */
 	NULL,				/* x */
 	NULL,				/* y */
-	NULL				/* z */
+	&sysrq_showwq_op		/* z */
 };
 
 /* key2index calculation, -1 on invalid index */
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 542526c..6ae9ebb 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -195,6 +195,7 @@ extern int schedule_on_each_cpu(work_func_t func);
 extern int current_is_keventd(void);
 extern int keventd_up(void);
 
+extern void show_workqueues(void);
 extern void init_workqueues(void);
 int execute_in_process_context(work_func_t fn, struct execute_work *);
 
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ff06611..c97d35d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -33,6 +33,7 @@
 #include <linux/kallsyms.h>
 #include <linux/debug_locks.h>
 #include <linux/lockdep.h>
+#include <linux/kallsyms.h>
 
 /*
  * The per-CPU workqueue (if single thread, we always use the first
@@ -867,6 +868,31 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 	return NOTIFY_OK;
 }
 
+void show_workqueues(void)
+{
+	struct workqueue_struct *wq;
+	int cpu;
+
+	spin_lock(&workqueue_lock);
+	list_for_each_entry(wq, &workqueues, list) {
+		printk("\n");
+		printk("Workqueue %s:\n", wq->name);
+		for_each_online_cpu(cpu) {
+			struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
+			struct work_struct *work;
+
+			printk("\tCPU %d ", cpu);
+			list_for_each_entry(work, &(cwq->worklist), entry) {
+				print_symbol("function %s", (unsigned long)work->func);
+			}
+			printk("\n");
+		}
+	}
+	spin_unlock(&workqueue_lock);
+	
+}
+EXPORT_SYMBOL(show_workqueues);
+
 void __init init_workqueues(void)
 {
 	cpu_populated_map = cpu_online_map;
---

diffstat wq.patch 
 drivers/char/sysrq.c      |   14 +++++++++++++-
 include/linux/workqueue.h |    1 +
 kernel/workqueue.c        |   26 ++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

Signed-off-by:  Frank Mayhar <fmayhar@google.com>
-- 
Frank Mayhar <fmayhar@google.com>
Google, Inc.