lockdep: check that no locks held at freeze time

We shouldn't try_to_freeze if locks are held.  Holding a lock can cause a
deadlock if the lock is later acquired in the suspend or hibernate path
(e.g.  by dpm).  Holding a lock can also cause a deadlock in the case of
cgroup_freezer if a lock is held inside a frozen cgroup that is later
acquired by a process outside that group.

[akpm@linux-foundation.org: export debug_check_no_locks_held]
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Ben Chan <benchan@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 14 insertions, 12 deletions

diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h
index 3bd46f766751..a975de1ff59f 100644
--- a/include/linux/debug_locks.h
+++ b/include/linux/debug_locks.h
@@ -51,7 +51,7 @@ struct task_struct;
 extern void debug_show_all_locks(void);
 extern void debug_show_held_locks(struct task_struct *task);
 extern void debug_check_no_locks_freed(const void *from, unsigned long len);
-extern void debug_check_no_locks_held(struct task_struct *task);
+extern void debug_check_no_locks_held(void);
 #else
 static inline void debug_show_all_locks(void)
 {
@@ -67,7 +67,7 @@ debug_check_no_locks_freed(const void *from, unsigned long len)
 }
 
 static inline void
-debug_check_no_locks_held(struct task_struct *task)
+debug_check_no_locks_held(void)
 {
 }
 #endif
diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index e70df40d84f6..043a5cf8b5ba 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -3,6 +3,7 @@
 #ifndef FREEZER_H_INCLUDED
 #define FREEZER_H_INCLUDED
 
+#include <linux/debug_locks.h>
 #include <linux/sched.h>
 #include <linux/wait.h>
 #include <linux/atomic.h>
@@ -48,6 +49,8 @@ extern void thaw_kernel_threads(void);
 
 static inline bool try_to_freeze(void)
 {
+        if (!(current->flags & PF_NOFREEZE))
+                debug_check_no_locks_held();
         might_sleep();
         if (likely(!freezing(current)))
                 return false;
diff --git a/kernel/exit.c b/kernel/exit.c
index 7dd20408707c..aaf97c122e8a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -835,7 +835,7 @@ void do_exit(long code)
         /*
          * Make sure we are holding no locks:
          */
-        debug_check_no_locks_held(tsk);
+        debug_check_no_locks_held();
         /*
          * We can do this unlocked here. The futex code uses this flag
          * just to verify whether the pi state cleanup has been done
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 8a0efac4f99d..259db207b5d9 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -4088,7 +4088,7 @@ void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
 }
 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
 
-static void print_held_locks_bug(struct task_struct *curr)
+static void print_held_locks_bug(void)
 {
         if (!debug_locks_off())
                 return;
@@ -4097,22 +4097,21 @@ static void print_held_locks_bug(struct task_struct *curr)
 
         printk("\n");
         printk("=====================================\n");
-        printk("[ BUG: lock held at task exit time! ]\n");
+        printk("[ BUG: %s/%d still has locks held! ]\n",
+               current->comm, task_pid_nr(current));
         print_kernel_ident();
         printk("-------------------------------------\n");
-        printk("%s/%d is exiting with locks still held!\n",
-                curr->comm, task_pid_nr(curr));
-        lockdep_print_held_locks(curr);
-
+        lockdep_print_held_locks(current);
         printk("\nstack backtrace:\n");
         dump_stack();
 }
 
-void debug_check_no_locks_held(struct task_struct *task)
+void debug_check_no_locks_held(void)
 {
-        if (unlikely(task->lockdep_depth > 0))
-                print_held_locks_bug(task);
+        if (unlikely(current->lockdep_depth > 0))
+                print_held_locks_bug();
 }
+EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
 
 void debug_show_all_locks(void)
 {