The patch titled
hibernate: fix lockdep report
has been added to the -mm tree. Its filename is
hibernate-fix-lockdep-report-2.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: hibernate: fix lockdep report
From: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Lockdep reports a circular locking dependency in the hibernate code
because
- during system boot hibernate code (from an initcall) locks pm_mutex
and then a sysfs buffer mutex via name_to_dev_t
- during regular operation hibernate code locks pm_mutex under a
sysfs buffer mutex because it's called from sysfs methods.
The deadlock can never happen because during initcall invocation nothing
can write to sysfs yet. This removes the lockdep report by marking the
initcall locking as being in a different class.
Signed-off-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Pavel Machek <pavel@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/power/disk.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff -puN kernel/power/disk.c~hibernate-fix-lockdep-report-2 kernel/power/disk.c
--- a/kernel/power/disk.c~hibernate-fix-lockdep-report-2
+++ a/kernel/power/disk.c
@@ -456,7 +456,17 @@ static int software_resume(void)
int error;
unsigned int flags;
- mutex_lock(&pm_mutex);
+ /*
+ * name_to_dev_t() below takes a sysfs buffer mutex when sysfs
+ * is configured into the kernel. Since the regular hibernate
+ * trigger path is via sysfs which takes a buffer mutex before
+ * calling hibernate functions (which take pm_mutex) this can
+ * cause lockdep to complain about a possible ABBA deadlock
+ * which cannot happen since we're in the boot code here and
+ * sysfs can't be invoked yet. Therefore, we use a subclass
+ * here to avoid lockdep complaining.
+ */
+ mutex_lock_nested(&pm_mutex, SINGLE_DEPTH_NESTING);
if (!swsusp_resume_device) {
if (!strlen(resume_file)) {
mutex_unlock(&pm_mutex);
_
Patches currently in -mm which might be from johannes@xxxxxxxxxxxxxxxx are
origin.patch
git-input.patch
fix-appletouch-geyser-1-breakage.patch
fix-appletouch-geyser-1-breakage-checkpatch-fixes.patch
git-kbuild.patch
git-wireless.patch
hibernate-fix-lockdep-report-2.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
