From: Johannes Berg Date: Thu, 15 Nov 2007 01:00:16 +0000 (-0800) Subject: hibernate: fix lockdep report X-Git-Tag: MMI-PSA29.97-13-9~38338 X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=60a0d23386eab0559ad32ae50b200cc58545f327;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git 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 --- diff --git a/kernel/power/disk.c b/kernel/power/disk.c index 8b15f777010a..05b64790fe83 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);