lockdep: re-annotate scheduler runqueues

Instead of using a per-rq lock class, use the regular nesting operations.

However, take extra care with double_lock_balance() as it can release the
already held rq->lock (and therefore change its nesting class).

So what can happen is:

 spin_lock(rq->lock);	// this rq subclass 0

 double_lock_balance(rq, other_rq);
   // release rq
   // acquire other_rq->lock subclass 0
   // acquire rq->lock subclass 1

 spin_unlock(other_rq->lock);

leaving you with rq->lock in subclass 1

So a subsequent double_lock_balance() call can try to nest a subclass 1
lock while already holding a subclass 1 lock.

Fix this by introducing double_unlock_balance() which releases the other
rq's lock, but also re-sets the subclass for this rq's lock to 0.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-08-11 09:30:22 +02:00 committed by Ingo Molnar
parent 64aa348edc
commit 1b12bbc747
2 changed files with 14 additions and 5 deletions

View file

@ -2812,6 +2812,13 @@ static int double_lock_balance(struct rq *this_rq, struct rq *busiest)
return ret; return ret;
} }
static void double_unlock_balance(struct rq *this_rq, struct rq *busiest)
__releases(busiest->lock)
{
spin_unlock(&busiest->lock);
lock_set_subclass(&this_rq->lock.dep_map, 0, _RET_IP_);
}
/* /*
* If dest_cpu is allowed for this process, migrate the task to it. * If dest_cpu is allowed for this process, migrate the task to it.
* This is accomplished by forcing the cpu_allowed mask to only * This is accomplished by forcing the cpu_allowed mask to only
@ -3636,7 +3643,7 @@ load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd,
ld_moved = move_tasks(this_rq, this_cpu, busiest, ld_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, CPU_NEWLY_IDLE, imbalance, sd, CPU_NEWLY_IDLE,
&all_pinned); &all_pinned);
spin_unlock(&busiest->lock); double_unlock_balance(this_rq, busiest);
if (unlikely(all_pinned)) { if (unlikely(all_pinned)) {
cpu_clear(cpu_of(busiest), *cpus); cpu_clear(cpu_of(busiest), *cpus);
@ -3751,7 +3758,7 @@ static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
else else
schedstat_inc(sd, alb_failed); schedstat_inc(sd, alb_failed);
} }
spin_unlock(&target_rq->lock); double_unlock_balance(busiest_rq, target_rq);
} }
#ifdef CONFIG_NO_HZ #ifdef CONFIG_NO_HZ

View file

@ -861,6 +861,8 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
#define RT_MAX_TRIES 3 #define RT_MAX_TRIES 3
static int double_lock_balance(struct rq *this_rq, struct rq *busiest); static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
static void double_unlock_balance(struct rq *this_rq, struct rq *busiest);
static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep); static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu) static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
@ -1022,7 +1024,7 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
break; break;
/* try again */ /* try again */
spin_unlock(&lowest_rq->lock); double_unlock_balance(rq, lowest_rq);
lowest_rq = NULL; lowest_rq = NULL;
} }
@ -1091,7 +1093,7 @@ static int push_rt_task(struct rq *rq)
resched_task(lowest_rq->curr); resched_task(lowest_rq->curr);
spin_unlock(&lowest_rq->lock); double_unlock_balance(rq, lowest_rq);
ret = 1; ret = 1;
out: out:
@ -1197,7 +1199,7 @@ static int pull_rt_task(struct rq *this_rq)
} }
skip: skip:
spin_unlock(&src_rq->lock); double_unlock_balance(this_rq, src_rq);
} }
return ret; return ret;