From: tip-bot for Alfredo Alvarez Fernandez <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: hpa@zytor.com, tglx@linutronix.de, linux-kernel@vger.kernel.org,
alfredoalvarezfernandez@gmail.com, mingo@kernel.org,
torvalds@linux-foundation.org, peterz@infradead.org
Subject: [tip:core/urgent] locking/lockdep: Print chain_key collision information
Date: Thu, 31 Mar 2016 23:36:43 -0700 [thread overview]
Message-ID: <tip-39e2e173fb1f900959d3a25c21c65fa88b06c6ee@git.kernel.org> (raw)
In-Reply-To: <1459357416-19190-1-git-send-email-alfredoalvarezernandez@gmail.com>
Commit-ID: 39e2e173fb1f900959d3a25c21c65fa88b06c6ee
Gitweb: http://git.kernel.org/tip/39e2e173fb1f900959d3a25c21c65fa88b06c6ee
Author: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
AuthorDate: Wed, 30 Mar 2016 19:03:36 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 31 Mar 2016 15:03:58 +0200
locking/lockdep: Print chain_key collision information
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.
This helps with debugging hash chain collision reports.
Signed-off-by: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-fsdevel@vger.kernel.org
Cc: sedat.dilek@gmail.com
Cc: tytso@mit.edu
Link: http://lkml.kernel.org/r/1459357416-19190-1-git-send-email-alfredoalvarezernandez@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/lockdep.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 77 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 53ab2f8..2324ba5 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2000,6 +2000,77 @@ 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 +2085,18 @@ 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;
next prev parent reply other threads:[~2016-04-01 6:37 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-27 8:15 [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 Sedat Dilek
2016-03-27 8:57 ` Sedat Dilek
2016-03-27 12:03 ` Linus Torvalds
2016-03-27 13:32 ` Boqun Feng
2016-03-27 18:23 ` Theodore Ts'o
2016-03-27 19:40 ` Sedat Dilek
[not found] ` <CA+55aFwoKRpgq8OCTxUaP+8gOg-mnN3nbruYgiK32a=C5U4TkQ@mail.gmail.com>
2016-03-27 20:24 ` Sedat Dilek
2016-03-27 20:48 ` Peter Zijlstra
2016-03-27 20:59 ` Sedat Dilek
2016-03-27 21:48 ` Sedat Dilek
2016-03-28 1:05 ` Boqun Feng
2016-03-28 6:33 ` Peter Zijlstra
2016-03-29 8:47 ` Ingo Molnar
2016-03-30 9:20 ` Sedat Dilek
2016-03-30 9:36 ` Sedat Dilek
2016-03-30 9:36 ` Peter Zijlstra
2016-03-30 9:49 ` Sedat Dilek
2016-03-30 10:33 ` Sedat Dilek
2016-03-30 12:43 ` Peter Zijlstra
2016-03-30 12:46 ` Sedat Dilek
2016-03-30 13:15 ` Peter Zijlstra
2016-03-30 9:50 ` Peter Zijlstra
2016-03-30 9:59 ` Boqun Feng
2016-03-30 10:36 ` Peter Zijlstra
2016-03-30 11:07 ` Sedat Dilek
2016-03-31 15:42 ` Peter Zijlstra
2016-03-31 15:52 ` Boqun Feng
2016-04-02 6:26 ` Sedat Dilek
2016-03-30 14:06 ` Peter Zijlstra
2016-03-30 15:21 ` Sedat Dilek
2016-03-30 17:03 ` [PATCH] lockdep: print chain_key collision information Alfredo Alvarez Fernandez
2016-03-30 17:19 ` Peter Zijlstra
2016-04-01 6:36 ` tip-bot for Alfredo Alvarez Fernandez [this message]
2016-05-10 9:09 ` [tip:core/urgent] locking/lockdep: Print " Peter Zijlstra
2016-04-04 15:31 ` [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 Sedat Dilek
2016-04-04 16:02 ` Peter Zijlstra
2016-05-09 11:37 ` Sedat Dilek
2016-06-03 15:15 ` Sedat Dilek
2016-04-23 12:54 ` [tip:locking/urgent] lockdep: Fix lock_chain::base size tip-bot for Peter Zijlstra
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