* Ingo Molnar <[EMAIL PROTECTED]> wrote:
> An updated patch is below. I also have boot tested it. Andrew, Linus,
> please apply.
this patch introduced a locking bug, which is fixed by the delta patch
below.
Ingo
------------------------>
Subject: [patch] lockdep: more unlock-on-error fixes, fix
From: Ingo Molnar <[EMAIL PROTECTED]>
my __acquire_lock() cleanup introduced a locking bug: on SMP
systems we'd release a non-owned graph lock. Fix this by
moving the graph unlock back, and by leaving the max_lockdep_depth
variable update possibly racy. (we dont care, it's just statistics)
also add some minimal debugging code to graph_unlock()/graph_lock(),
which caught this locking bug.
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
---
kernel/lockdep.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
Index: linux/kernel/lockdep.c
===================================================================
--- linux.orig/kernel/lockdep.c
+++ linux/kernel/lockdep.c
@@ -70,6 +70,9 @@ static int graph_lock(void)
static inline int graph_unlock(void)
{
+ if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
+ return DEBUG_LOCKS_WARN_ON(1);
+
__raw_spin_unlock(&lockdep_lock);
return 0;
}
@@ -716,6 +719,9 @@ find_usage_backwards(struct lock_class *
struct lock_list *entry;
int ret;
+ if (!__raw_spin_is_locked(&lockdep_lock))
+ return DEBUG_LOCKS_WARN_ON(1);
+
if (depth > max_recursion_depth)
max_recursion_depth = depth;
if (depth >= RECURSION_LIMIT)
@@ -2208,6 +2214,7 @@ out_calc_hash:
if (!chain_head && ret != 2)
if (!check_prevs_add(curr, hlock))
return 0;
+ graph_unlock();
} else
/* after lookup_chain_cache(): */
if (unlikely(!debug_locks))
@@ -2216,7 +2223,7 @@ out_calc_hash:
curr->lockdep_depth++;
check_chain_key(curr);
if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
- debug_locks_off_graph_unlock();
+ debug_locks_off();
printk("BUG: MAX_LOCK_DEPTH too low!\n");
printk("turning off the locking correctness validator.\n");
return 0;
@@ -2225,7 +2232,6 @@ out_calc_hash:
if (unlikely(curr->lockdep_depth > max_lockdep_depth))
max_lockdep_depth = curr->lockdep_depth;
- graph_unlock();
return 1;
}
-
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