From 9f966d591e3db6b6b980a8f4b09833ab39f58266 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Wed, 14 Nov 2007 17:00:16 -0800 Subject: [PATCH] hibernate: fix lockdep report 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 Cc: "Rafael J. Wysocki" Cc: Alan Stern Acked-by: Peter Zijlstra Cc: Pavel Machek Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/power/disk.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/kernel/power/disk.c b/kernel/power/disk.c index 8b15f777010a9..05b64790fe839 100644 --- a/kernel/power/disk.c +++ b/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); -- 2.39.5