Messages in this thread Patch in this message | | | Subject | [PATCH] make lockdep happy with r/o bind mounts | From | Dave Hansen <> | Date | Mon, 24 Sep 2007 10:46:58 -0700 |
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With the r/o bind mount patches, we can have as many spinlocks nested as there are CPUs on the system. Lockdep freaks out after 8.
So, create a new lockdep class of locks for the mnt_writer spinlocks, and initialize each of the cpu locks to be in a different class.
It should shut up warnings like this, while still allowing some of the lockdep goodness to remain:
============================================= [ INFO: possible recursive locking detected ] 2.6.23-rc6 #6 --------------------------------------------- swapper/1 is trying to acquire lock: (&writer->lock){--..}, at: [<c016c094>] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c
but task is already holding lock: (&writer->lock){--..}, at: [<c016c094>] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c
other info that might help us debug this: 1 lock held by swapper/1: #0: (&writer->lock){--..}, at: [<c016c094>] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c
stack backtrace: [<c01034ab>] show_trace_log_lvl+0x19/0x2e [<c01034d2>] show_trace+0x12/0x14 [<c01035be>] dump_stack+0x14/0x16 [<c0130ab2>] print_deadlock_bug+0xb7/0xc1 [<c0130afc>] check_deadlock+0x40/0x54 [<c013100a>] validate_chain+0x26e/0x319 [<c0132cca>] __lock_acquire+0x6c4/0x731 [<c01332da>] lock_acquire+0x7a/0x94 [<c031bb01>] _spin_lock+0x38/0x62 [<c016c094>] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c [<c016c5f8>] mntput_no_expire+0x38/0xad [<c015fbed>] path_release_on_umount+0x15/0x18 [<c016cc76>] sys_umount+0x67/0x6f [<c010058a>] name_to_dev_t+0x22a/0x24c [<c0427207>] prepare_namespace+0x89/0x187 [<c0426cdd>] kernel_init+0x9a/0xa3 [<c010336f>] kernel_thread_helper+0x7/0x10 =======================
Signed-off-by: Dave Hansen <haveblue@us.ibm.com> ---
lxc-dave/fs/namespace.c | 2 ++ 1 file changed, 2 insertions(+)
diff -puN fs/namespace.c~make-lockdep-happy-with-ro-bind-mounts fs/namespace.c --- lxc/fs/namespace.c~make-lockdep-happy-with-ro-bind-mounts 2007-09-24 10:32:23.000000000 -0700 +++ lxc-dave/fs/namespace.c 2007-09-24 10:41:37.000000000 -0700 @@ -116,6 +116,7 @@ struct mnt_writer { * must be ordered by cpu number. */ spinlock_t lock; + struct lock_class_key lock_class; /* compiles out with !lockdep */ unsigned long count; struct vfsmount *mnt; } ____cacheline_aligned_in_smp; @@ -127,6 +128,7 @@ static int __init init_mnt_writers(void) for_each_possible_cpu(cpu) { struct mnt_writer *writer = &per_cpu(mnt_writers, cpu); spin_lock_init(&writer->lock); + lockdep_set_class(&writer->lock, &writer->lock_class); writer->count = 0; } return 0; diff -puN include/linux/lockdep.h~make-lockdep-happy-with-ro-bind-mounts include/linux/lockdep.h _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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