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>

diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h
index 3bd46f7..a975de1 100644 (file)
--- 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 e70df40..043a5cf 100644 (file)
--- 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 7dd2040..aaf97c1 100644 (file)
--- 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 8a0efac..259db20 100644 (file)
--- 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)
 {