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Commit 6aa97070 authored by Mandeep Singh Baines's avatar Mandeep Singh Baines Committed by Linus Torvalds
Browse files

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: default avatarMandeep 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c2c1b089

include/linux/debug_locks.h

+2 −2
Original line number Diff line number Diff line
@@ -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

include/linux/freezer.h

+3 −0
Original line number Diff line number Diff line
@@ -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;

kernel/exit.c

+1 −1
Original line number Diff line number Diff line
@@ -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

kernel/lockdep.c

+8 −9
Original line number Diff line number Diff line
@@ -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)

{