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Commit e0944ee6 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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lockdep: Remove cmpxchg to update nr_chain_hlocks 



For some reason nr_chain_hlocks is updated with cmpxchg, but
this is performed inside of the lockdep global "grab_lock()",
which also makes simple modification of this variable atomic.

Remove the cmpxchg logic for updating nr_chain_hlocks and
simplify the code.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110421014300.727863282@goodmis.org


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 282b5c2f

kernel/lockdep.c

+4 −10
Original line number Original line Diff line number Diff line
@@ -1973,7 +1973,7 @@ static inline int lookup_chain_cache(struct task_struct *curr, 
	struct list_head *hash_head = chainhashentry(chain_key);

	struct list_head *hash_head = chainhashentry(chain_key);

	struct lock_chain *chain;

	struct lock_chain *chain;

	struct held_lock *hlock_curr, *hlock_next;

	struct held_lock *hlock_curr, *hlock_next;

	int i, j, n, cn;

	int i, j;





	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))

	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))

		return 0;

		return 0;
@@ -2033,15 +2033,9 @@ static inline int lookup_chain_cache(struct task_struct *curr, 
	}

	}

	i++;

	i++;

	chain->depth = curr->lockdep_depth + 1 - i;

	chain->depth = curr->lockdep_depth + 1 - i;

	cn = nr_chain_hlocks;

	if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {

	while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {

		chain->base = nr_chain_hlocks;

		n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);

		nr_chain_hlocks += chain->depth;

		if (n == cn)

			break;

		cn = n;

	}

	if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {

		chain->base = cn;

		for (j = 0; j < chain->depth - 1; j++, i++) {

		for (j = 0; j < chain->depth - 1; j++, i++) {

			int lock_id = curr->held_locks[i].class_idx - 1;

			int lock_id = curr->held_locks[i].class_idx - 1;

			chain_hlocks[chain->base + j] = lock_id;

			chain_hlocks[chain->base + j] = lock_id;