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author | Michael Holzheu <holzheu@linux.vnet.ibm.com> | 2012-12-20 16:30:52 (GMT) |
---|---|---|
committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2013-01-08 09:57:03 (GMT) |
commit | 5a334c082fc91f0c342ba9c111b77cafb5266654 (patch) | |
tree | 9737eb815316b19b7bbea43b1a495e532e5adc78 | |
parent | 2a893f91f57314c593f36cee689ad6e353af9daf (diff) | |
download | linux-5a334c082fc91f0c342ba9c111b77cafb5266654.tar.xz |
s390/debug: Fix s390dbf lockdep problem in debug_(un)register_view()
The debug_register/unregister_view() functions call debugfs_remove()
while holding the debug_info spinlock. Because debugfs_remove() takes
a mutex and therefore can sleep this is not allowed. To fix the problem
we give up the debug_info lock before calling debugfs_remove().
The following shows the lockdep message:
[ INFO: possible circular locking dependency detected ]
-------------------------------------------------------
rmmod/4379 is trying to acquire lock:
(&sb->s_type->i_mutex_key#2){+.+.+.}, at: [<00000000003acae2>] debugfs_remove+0x5e/0xa
but task is already holding lock:
(&(&rc->lock)->rlock){-.-...}, at: [<000000000010a5ae>] debug_unregister_view+0x3a/0xd
which lock already depends on the new lock.
-> #0 (&sb->s_type->i_mutex_key#2){+.+.+.}:
[<00000000001b1644>] validate_chain+0x880/0x1154
[<00000000001b4d6c>] __lock_acquire+0x414/0xc44
[<00000000001b5c16>] lock_acquire+0xbe/0x178
[<0000000000614016>] mutex_lock_nested+0x66/0x36c
[<00000000003acae2>] debugfs_remove+0x5e/0xac
[<000000000010a620>] debug_unregister_view+0xac/0xd0
[<000003ff8002f140>] qeth_core_exit+0x48/0xf08 [qeth]
[<00000000001c35a4>] SyS_delete_module+0x1a4/0x260
[<0000000000618134>] sysc_noemu+0x22/0x28
[<000003fffd4704da>] 0x3fffd4704da
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
-rw-r--r-- | arch/s390/kernel/debug.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c index ba500d8..4e8215e 100644 --- a/arch/s390/kernel/debug.c +++ b/arch/s390/kernel/debug.c @@ -1127,13 +1127,14 @@ debug_register_view(debug_info_t * id, struct debug_view *view) if (i == DEBUG_MAX_VIEWS) { pr_err("Registering view %s/%s would exceed the maximum " "number of views %i\n", id->name, view->name, i); - debugfs_remove(pde); rc = -1; } else { id->views[i] = view; id->debugfs_entries[i] = pde; } spin_unlock_irqrestore(&id->lock, flags); + if (rc) + debugfs_remove(pde); out: return rc; } @@ -1146,9 +1147,9 @@ EXPORT_SYMBOL(debug_register_view); int debug_unregister_view(debug_info_t * id, struct debug_view *view) { - int rc = 0; - int i; + struct dentry *dentry = NULL; unsigned long flags; + int i, rc = 0; if (!id) goto out; @@ -1160,10 +1161,12 @@ debug_unregister_view(debug_info_t * id, struct debug_view *view) if (i == DEBUG_MAX_VIEWS) rc = -1; else { - debugfs_remove(id->debugfs_entries[i]); + dentry = id->debugfs_entries[i]; id->views[i] = NULL; + id->debugfs_entries[i] = NULL; } spin_unlock_irqrestore(&id->lock, flags); + debugfs_remove(dentry); out: return rc; } |