Messages in this thread Patch in this message | | | Date | Fri, 18 May 2012 14:16:33 -0700 | From | Greg KH <> | Subject | [ 34/54] jffs2: Fix lock acquisition order bug in gc path |
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3.0-stable review patch. If anyone has any objections, please let me know.
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From: Josh Cartwright <joshc@linux.com>
commit 226bb7df3d22bcf4a1c0fe8206c80cc427498eae upstream.
The locking policy is such that the erase_complete_block spinlock is nested within the alloc_sem mutex. This fixes a case in which the acquisition order was erroneously reversed. This issue was caught by the following lockdep splat:
======================================================= [ INFO: possible circular locking dependency detected ] 3.0.5 #1 ------------------------------------------------------- jffs2_gcd_mtd6/299 is trying to acquire lock: (&c->alloc_sem){+.+.+.}, at: [<c01f7714>] jffs2_garbage_collect_pass+0x314/0x890
but task is already holding lock: (&(&c->erase_completion_lock)->rlock){+.+...}, at: [<c01f7708>] jffs2_garbage_collect_pass+0x308/0x890
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&(&c->erase_completion_lock)->rlock){+.+...}: [<c008bec4>] validate_chain+0xe6c/0x10bc [<c008c660>] __lock_acquire+0x54c/0xba4 [<c008d240>] lock_acquire+0xa4/0x114 [<c046780c>] _raw_spin_lock+0x3c/0x4c [<c01f744c>] jffs2_garbage_collect_pass+0x4c/0x890 [<c01f937c>] jffs2_garbage_collect_thread+0x1b4/0x1cc [<c0071a68>] kthread+0x98/0xa0 [<c000f264>] kernel_thread_exit+0x0/0x8
-> #0 (&c->alloc_sem){+.+.+.}: [<c008ad2c>] print_circular_bug+0x70/0x2c4 [<c008c08c>] validate_chain+0x1034/0x10bc [<c008c660>] __lock_acquire+0x54c/0xba4 [<c008d240>] lock_acquire+0xa4/0x114 [<c0466628>] mutex_lock_nested+0x74/0x33c [<c01f7714>] jffs2_garbage_collect_pass+0x314/0x890 [<c01f937c>] jffs2_garbage_collect_thread+0x1b4/0x1cc [<c0071a68>] kthread+0x98/0xa0 [<c000f264>] kernel_thread_exit+0x0/0x8
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&(&c->erase_completion_lock)->rlock); lock(&c->alloc_sem); lock(&(&c->erase_completion_lock)->rlock); lock(&c->alloc_sem);
*** DEADLOCK ***
1 lock held by jffs2_gcd_mtd6/299: #0: (&(&c->erase_completion_lock)->rlock){+.+...}, at: [<c01f7708>] jffs2_garbage_collect_pass+0x308/0x890
stack backtrace: [<c00155dc>] (unwind_backtrace+0x0/0x100) from [<c0463dc0>] (dump_stack+0x20/0x24) [<c0463dc0>] (dump_stack+0x20/0x24) from [<c008ae84>] (print_circular_bug+0x1c8/0x2c4) [<c008ae84>] (print_circular_bug+0x1c8/0x2c4) from [<c008c08c>] (validate_chain+0x1034/0x10bc) [<c008c08c>] (validate_chain+0x1034/0x10bc) from [<c008c660>] (__lock_acquire+0x54c/0xba4) [<c008c660>] (__lock_acquire+0x54c/0xba4) from [<c008d240>] (lock_acquire+0xa4/0x114) [<c008d240>] (lock_acquire+0xa4/0x114) from [<c0466628>] (mutex_lock_nested+0x74/0x33c) [<c0466628>] (mutex_lock_nested+0x74/0x33c) from [<c01f7714>] (jffs2_garbage_collect_pass+0x314/0x890) [<c01f7714>] (jffs2_garbage_collect_pass+0x314/0x890) from [<c01f937c>] (jffs2_garbage_collect_thread+0x1b4/0x1cc) [<c01f937c>] (jffs2_garbage_collect_thread+0x1b4/0x1cc) from [<c0071a68>] (kthread+0x98/0xa0) [<c0071a68>] (kthread+0x98/0xa0) from [<c000f264>] (kernel_thread_exit+0x0/0x8)
This was introduce in '81cfc9f jffs2: Fix serious write stall due to erase'.
Signed-off-by: Josh Cartwright <joshc@linux.com> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/jffs2/gc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/jffs2/gc.c +++ b/fs/jffs2/gc.c @@ -225,8 +225,8 @@ int jffs2_garbage_collect_pass(struct jf return 0; D1(printk(KERN_DEBUG "No progress from erasing blocks; doing GC anyway\n")); - spin_lock(&c->erase_completion_lock); mutex_lock(&c->alloc_sem); + spin_lock(&c->erase_completion_lock); } /* First, work out which block we're garbage-collecting */
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