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Groups > linux.kernel > #1367466
| From | Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH] lockdep: print chain_key collision information |
| Date | 2016-03-30 19:10 +0200 |
| Message-ID | <rirN0-87-17@gated-at.bofh.it> (permalink) |
| References | <riqee-7pH-19@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
A sequence of pairs [class_idx -> corresponding chain_key iteration]
is printed for both the current held_lock chain and the cached chain.
That exposes the two different class_idx sequences that led to that
particular hash value.
Signed-off-by: Alfredo Alvarez Fernandez <alfredoalvarezernandez@gmail.com>
---
kernel/locking/lockdep.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 79 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 53ab2f8..5af260f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2000,6 +2000,79 @@ static inline int get_first_held_lock(struct task_struct *curr,
}
/*
+ * Returns the next chain_key iteration
+ */
+static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
+{
+ u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
+
+ printk(" class_idx:%d -> chain_key:%016Lx",
+ class_idx,
+ (unsigned long long)new_chain_key);
+ return new_chain_key;
+}
+
+static void print_chain_keys_held_locks(struct task_struct *curr,
+ struct held_lock *hlock_next)
+{
+ struct held_lock *hlock;
+ u64 chain_key = 0;
+ int depth = curr->lockdep_depth;
+ int i;
+
+ printk("depth: %u\n", depth + 1);
+ for (i = get_first_held_lock(curr, hlock_next); i < depth; i++) {
+ hlock = curr->held_locks + i;
+ chain_key = print_chain_key_iteration(hlock->class_idx,
+ chain_key);
+
+ print_lock(hlock);
+ }
+
+ print_chain_key_iteration(hlock_next->class_idx, chain_key);
+ print_lock(hlock_next);
+}
+
+static void print_chain_keys_chain(struct lock_chain *chain)
+{
+ int i;
+ u64 chain_key = 0;
+ int class_id;
+
+ printk("depth: %u\n", chain->depth);
+ for (i = 0; i < chain->depth; i++) {
+ class_id = chain_hlocks[chain->base + i];
+ chain_key = print_chain_key_iteration(class_id + 1,
+ chain_key);
+
+ print_lock_name(lock_classes + class_id);
+ printk("\n");
+ }
+}
+
+static void print_collision(struct task_struct *curr,
+ struct held_lock *hlock_next,
+ struct lock_chain *chain)
+{
+ printk("\n");
+ printk("======================\n");
+ printk("[chain_key collision ]\n");
+ print_kernel_ident();
+ printk("----------------------\n");
+ printk("%s/%d: ", current->comm, task_pid_nr(current));
+ printk("Hash chain already cached but the contents don't match!\n");
+
+ printk("Held locks:");
+ print_chain_keys_held_locks(curr, hlock_next);
+
+ printk("Locks in cached chain:");
+ print_chain_keys_chain(chain);
+
+ printk("\nstack backtrace:\n");
+ dump_stack();
+}
+
+/*
* Checks whether the chain and the current held locks are consistent
* in depth and also in content. If they are not it most likely means
* that there was a collision during the calculation of the chain_key.
@@ -2014,14 +2087,18 @@ static int check_no_collision(struct task_struct *curr,
i = get_first_held_lock(curr, hlock);
- if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1)))
+ if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
+ print_collision(curr, hlock, chain);
return 0;
+ }
for (j = 0; j < chain->depth - 1; j++, i++) {
id = curr->held_locks[i].class_idx - 1;
- if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id))
+ if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
+ print_collision(curr, hlock, chain);
return 0;
+ }
}
#endif
return 1;
--
2.5.0
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[PATCH] lockdep: print chain_key collision information Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com> - 2016-03-30 19:10 +0200
Re: [PATCH] lockdep: print chain_key collision information Peter Zijlstra <peterz@infradead.org> - 2016-03-30 19:20 +0200
[tip:core/urgent] locking/lockdep: Print chain_key collision information tip-bot for Alfredo Alvarez Fernandez <tipbot@zytor.com> - 2016-04-01 08:40 +0200
Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 Sedat Dilek <sedat.dilek@gmail.com> - 2016-03-30 11:40 +0200
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