lockdep: change scheduler annotation (5e710e37) · Commits · 戴 / test

While thinking about David's graph walk lockdep patch it _finally_ dawned on me that there is no reason we have a lock class per cpu ... Sorry for being dense :-/ The below changes the annotation from a lock class per cpu, to a single nested lock, as the scheduler never holds more that 2 rq locks at a time anyway. If there was code requiring holding all rq locks this would not work and the original annotation would be the only option, but that not being the case, this is a much lighter one. Compiles and boots on a 2-way x86_64. Signed-off-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: David Miller <davem@davemloft.net> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/sched.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -600,7 +600,6 @@ struct rq {
		/* BKL stats */
		unsigned int bkl_count;
		#endif
		struct lock_class_key rq_lock_key;
		};

		static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
		@@ -2759,10 +2758,10 @@ static void double_rq_lock(struct rq rq1, struct rq rq2)
		} else {
		if (rq1 < rq2) {
		spin_lock(&rq1->lock);
		spin_lock(&rq2->lock);
		spin_lock_nested(&rq2->lock, SINGLE_DEPTH_NESTING);
		} else {
		spin_lock(&rq2->lock);
		spin_lock(&rq1->lock);
		spin_lock_nested(&rq1->lock, SINGLE_DEPTH_NESTING);
		}
		}
		update_rq_clock(rq1);
		@@ -2805,10 +2804,10 @@ static int double_lock_balance(struct rq this_rq, struct rq busiest)
		if (busiest < this_rq) {
		spin_unlock(&this_rq->lock);
		spin_lock(&busiest->lock);
		spin_lock(&this_rq->lock);
		spin_lock_nested(&this_rq->lock, SINGLE_DEPTH_NESTING);
		ret = 1;
		} else
		spin_lock(&busiest->lock);
		spin_lock_nested(&busiest->lock, SINGLE_DEPTH_NESTING);
		}
		return ret;
		}
		@@ -7998,7 +7997,6 @@ void __init sched_init(void)

		rq = cpu_rq(i);
		spin_lock_init(&rq->lock);
		lockdep_set_class(&rq->lock, &rq->rq_lock_key);
		rq->nr_running = 0;
		init_cfs_rq(&rq->cfs, rq);
		init_rt_rq(&rq->rt, rq);

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