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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>
This commit is contained in:
Alfredo Alvarez Fernandez 2016-03-30 19:03:36 +02:00 committed by Ingo Molnar
parent 283d757378
commit 39e2e173fb
1 changed files with 77 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
kernel/locking/lockdep.c
View File

@ -1999,6 +1999,77 @@ static inline int get_first_held_lock(struct task_struct *curr,
return ++i;
}
/*
* 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
@ -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;