[PATCH] device_shutdown can loop if the driver frees itself

[PATCH] device_shutdown can loop if the driver frees itself

[Michael Richardson]

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This patch changes device_shutdown() to use a newly introduce safe
reverse list traversal.  We experienced loops on system reboot if we had
removed and re-inserted our device from the device list. 

We noticed this problem on PPC405. Our PCI IDE device comes and goes a lot.

Our hypothesis was that there was a loop caused by the driver->shutdown
freeing memory.  It is possible that we do something wrong as well, but
being unable to reboot is kind of nasty.

Signed-off-by: Michael Richardson <mcr@marajade.sandelman.ca>

---

 drivers/base/power/shutdown.c |    4 ++--
 include/linux/list.h          |   13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

applies-to: 96a0b5842e24d6736c698cdbd820a3ad9d8d9f10
49291875d63ec697510fc4cc9a1766b7400ee2d3
diff --git a/drivers/base/power/shutdown.c b/drivers/base/power/shutdown.c
index f50a08b..3a417c8 100644
--- a/drivers/base/power/shutdown.c
+++ b/drivers/base/power/shutdown.c
@@ -35,10 +35,10 @@ extern int sysdev_shutdown(void);
  */
 void device_shutdown(void)
 {
-	struct device * dev;
+	struct device * dev, *devn;
 
 	down_write(&devices_subsys.rwsem);
-	list_for_each_entry_reverse(dev, &devices_subsys.kset.list,
+	list_for_each_entry_safe_reverse(dev, devn, &devices_subsys.kset.list,
 				kobj.entry) {
 		if (dev->driver && dev->driver->shutdown) {
 			dev_dbg(dev, "shutdown\n");
diff --git a/include/linux/list.h b/include/linux/list.h
index 8e33882..b31ec32 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -436,6 +436,19 @@ static inline void list_splice_init(stru
 	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
 
 /**
+ * list_for_each_entry_safe_reverse - iterate backwards over list of given type safe against removal of list entry
+ * @pos:	the type * to use as a loop counter.
+ * @n:          another type * to use as temporary storage
+ * @head:	the head for your list.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_for_each_entry_safe_reverse(pos, n, head, member)		\
+	for (pos = list_entry((head)->prev, typeof(*pos), member),	\
+		     n = list_entry(pos->member.next, typeof(*pos), member); \
+	     &pos->member != (head); 	\
+	     pos = n, n = list_entry(n->member.prev, typeof(*n), member))
+
+/**
  * list_for_each_rcu	-	iterate over an rcu-protected list
  * @pos:	the &struct list_head to use as a loop counter.
  * @head:	the head for your list.
---
0.99.9.GIT







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[PATCH] device_shutdown can loop if the driver frees itself

[Greg KH]

[PATCH] device_shutdown can loop if the driver frees itself

This patch changes device_shutdown() to use the newly introduced safe
reverse list traversal.  We experienced loops on system reboot if we had
removed and re-inserted our device from the device list.

We noticed this problem on PPC405. Our PCI IDE device comes and goes a lot.

Our hypothesis was that there was a loop caused by the driver->shutdown
freeing memory.  It is possible that we do something wrong as well, but
being unable to reboot is kind of nasty.

Signed-off-by: Michael Richardson <mcr@marajade.sandelman.ca>
Cc: Patrick Mochel <mochel@digitalimplant.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
commit 9c08a938ce5a3e1c9d5f764dc6ae844cb1af76ff
tree 9bd0a984b2e5466454e2633783786a516fe14484
parent 2d7b5a70e01ff8b1b054d8313362e454e3057c5a
author Michael Richardson <mcr@sandelman.ottawa.on.ca> Mon, 09 Jan 2006 01:04:51 -0800
committer Greg Kroah-Hartman <gregkh@suse.de> Fri, 13 Jan 2006 11:26:12 -0800

 drivers/base/power/shutdown.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/shutdown.c b/drivers/base/power/shutdown.c
index a47bb74..c2475f3 100644
--- a/drivers/base/power/shutdown.c
+++ b/drivers/base/power/shutdown.c
@@ -35,10 +35,10 @@ extern int sysdev_shutdown(void);
  */
 void device_shutdown(void)
 {
-	struct device * dev;
+	struct device * dev, *devn;
 
 	down_write(&devices_subsys.rwsem);
-	list_for_each_entry_reverse(dev, &devices_subsys.kset.list,
+	list_for_each_entry_safe_reverse(dev, devn, &devices_subsys.kset.list,
 				kobj.entry) {
 		if (dev->bus && dev->bus->shutdown) {
 			dev_dbg(dev, "shutdown\n");