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authorMichael Holzheu <holzheu@linux.vnet.ibm.com>2012-12-20 17:30:52 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-01-08 10:57:03 +0100
commit5a334c082fc91f0c342ba9c111b77cafb5266654 (patch)
tree9737eb815316b19b7bbea43b1a495e532e5adc78 /arch
parent2a893f91f57314c593f36cee689ad6e353af9daf (diff)
downloadvexpress-lsk-5a334c082fc91f0c342ba9c111b77cafb5266654.tar.gz
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/kernel/debug.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index ba500d8dc39..4e8215e0d4b 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;
}