lockdep: Remove cmpxchg to update nr_chain_hlocks (e0944ee6) · Commits · 戴 / test

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:

Steven Rostedt <rostedt@goodmis.org> Acked-by:

Peter 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:

Ingo Molnar <mingo@elte.hu>

kernel/lockdep.c

+4 −10

Original line number	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 lock_chain *chain;
		struct held_lock hlock_curr, hlock_next;
		int i, j, n, cn;
		int i, j;

		if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
		return 0;
		@@ -2033,15 +2033,9 @@ cache_hit:
		}
		i++;
		chain->depth = curr->lockdep_depth + 1 - i;
		cn = nr_chain_hlocks;
		while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
		n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
		if (n == cn)
		break;
		cn = n;
		}
		if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
		chain->base = cn;
		if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
		chain->base = nr_chain_hlocks;
		nr_chain_hlocks += chain->depth;
		for (j = 0; j < chain->depth - 1; j++, i++) {
		int lock_id = curr->held_locks[i].class_idx - 1;
		chain_hlocks[chain->base + j] = lock_id;

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