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Subject[PATCH] lockdep: make lock held while freezing check optional
Date
This check is turning up a lot of code paths which need to be
fixed so while those paths are fixed, let's make this check
optional so that folks can still use lockdep.

CC: Tejun Heo <tj@kernel.org>
CC: Jeff Layton <jlayton@redhat.com>
CC: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Ming Lei <ming.lei@canonical.com>
CC: "Rafael J. Wysocki" <rjw@sisk.pl>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Ingo Molnar <mingo@redhat.com>
---
include/linux/freezer.h | 2 ++
lib/Kconfig.debug | 12 ++++++++++++
2 files changed, 14 insertions(+)

diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index 043a5cf..03bdc54 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -49,8 +49,10 @@ extern void thaw_kernel_threads(void);

static inline bool try_to_freeze(void)
{
+#ifdef CONFIG_DEBUG_LOCK_HELD_FREEZING
if (!(current->flags & PF_NOFREEZE))
debug_check_no_locks_held();
+#endif
might_sleep();
if (likely(!freezing(current)))
return false;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 28be08c..bddda5f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -547,6 +547,18 @@ config DEBUG_MUTEXES
This feature allows mutex semantics violations to be detected and
reported.

+config DEBUG_LOCK_HELD_FREEZING
+ bool "Lock debugging: detect when locks are held during freeze"
+ depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
+ select DEBUG_SPINLOCK
+ select DEBUG_MUTEXES
+ select LOCKDEP
+ help
+ This feature will check whether any lock is incorrectly held
+ while freezing. If a task freezes with a lock held it will
+ block any other task that is waiting on that lock from freezing.
+ In the case of cgroup_freezer, this can cause a deadlock.
+
config DEBUG_LOCK_ALLOC
bool "Lock debugging: detect incorrect freeing of live locks"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
--
1.7.12.4


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