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authorIngo Molnar <mingo@elte.hu>2006-10-17 00:09:28 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-17 08:18:42 -0700
commitca268c691de95612981b93e58899c1d73fdb6b47 (patch)
tree5bffd6512113613ae9c3dfd0e8b19a14d8e64856
parent623a43952abfad2d48f287d1fab07b2089d07554 (diff)
[PATCH] lockdep: increase max allowed recursion depth
In general, lockdep warnings are intended to be non-fatal, so I have put in various practical limits on internal data structure failure modes. We haven't had a /single/ lockdep-internal crash ever since lockdep went upstream [the unwinder crashes are outside of lockdep], and that's largely due to the good internal checks it does. Recursion within the dependency graph is currently limited to 20, that's probably not enough on some many-CPU boxes - this patch doubles it to 40. I have written the lockdep functions to have as small stackframes as possible, so 40 should be OK too. (The practical recursion limit should be somewhere between 100 and 200 entries. If we hit that then I'll change the algorithm to be iteration-based. Graph walking logic is so easy to program via recursion, so i'd like to keep recursion as long as possible.) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--kernel/lockdep.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 805a322a565..d1a3b2cfe4a 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -575,6 +575,8 @@ static noinline int print_circular_bug_tail(void)
return 0;
}
+#define RECURSION_LIMIT 40
+
static int noinline print_infinite_recursion_bug(void)
{
__raw_spin_unlock(&hash_lock);
@@ -595,7 +597,7 @@ check_noncircular(struct lock_class *source, unsigned int depth)
debug_atomic_inc(&nr_cyclic_check_recursions);
if (depth > max_recursion_depth)
max_recursion_depth = depth;
- if (depth >= 20)
+ if (depth >= RECURSION_LIMIT)
return print_infinite_recursion_bug();
/*
* Check this lock's dependency list:
@@ -645,7 +647,7 @@ find_usage_forwards(struct lock_class *source, unsigned int depth)
if (depth > max_recursion_depth)
max_recursion_depth = depth;
- if (depth >= 20)
+ if (depth >= RECURSION_LIMIT)
return print_infinite_recursion_bug();
debug_atomic_inc(&nr_find_usage_forwards_checks);
@@ -684,7 +686,7 @@ find_usage_backwards(struct lock_class *source, unsigned int depth)
if (depth > max_recursion_depth)
max_recursion_depth = depth;
- if (depth >= 20)
+ if (depth >= RECURSION_LIMIT)
return print_infinite_recursion_bug();
debug_atomic_inc(&nr_find_usage_backwards_checks);