Commit 60e69eed authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

sched/numa: Fix task_numa_free() lockdep splat 



Sasha reported that lockdep claims that the following commit:
made numa_group.lock interrupt unsafe:

  156654f4 ("sched/numa: Move task_numa_free() to __put_task_struct()")

While I don't see how that could be, given the commit in question moved
task_numa_free() from one irq enabled region to another, the below does
make both gripes and lockups upon gripe with numa=fake=4 go away.

Reported-by: default avatarSasha Levin <sasha.levin@oracle.com>
Fixes: 156654f4 ("sched/numa: Move task_numa_free() to __put_task_struct()")
Signed-off-by: default avatarMike Galbraith <bitbucket@online.de>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: torvalds@linux-foundation.org
Cc: mgorman@suse.com
Cc: akpm@linux-foundation.org
Cc: Dave Jones <davej@redhat.com>
Link: http://lkml.kernel.org/r/1396860915.5170.5.camel@marge.simpson.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 467cbd20

kernel/sched/fair.c

+7 −6
Original line number Diff line number Diff line
@@ -1497,7 +1497,7 @@ static void task_numa_placement(struct task_struct *p) 
	/* If the task is part of a group prevent parallel updates to group stats */

	if (p->numa_group) {

		group_lock = &p->numa_group->lock;

		spin_lock(group_lock);

		spin_lock_irq(group_lock);

	}



	/* Find the node with the highest number of faults */
@@ -1572,7 +1572,7 @@ static void task_numa_placement(struct task_struct *p) 
			}

		}



		spin_unlock(group_lock);

		spin_unlock_irq(group_lock);

	}



	/* Preferred node as the node with the most faults */
@@ -1677,7 +1677,8 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags, 
	if (!join)

		return;



	double_lock(&my_grp->lock, &grp->lock);

	BUG_ON(irqs_disabled());

	double_lock_irq(&my_grp->lock, &grp->lock);



	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {

		my_grp->faults[i] -= p->numa_faults_memory[i];
@@ -1691,7 +1692,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags, 
	grp->nr_tasks++;



	spin_unlock(&my_grp->lock);

	spin_unlock(&grp->lock);

	spin_unlock_irq(&grp->lock);



	rcu_assign_pointer(p->numa_group, grp);
@@ -1710,14 +1711,14 @@ void task_numa_free(struct task_struct *p) 
	void *numa_faults = p->numa_faults_memory;



	if (grp) {

		spin_lock(&grp->lock);

		spin_lock_irq(&grp->lock);

		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)

			grp->faults[i] -= p->numa_faults_memory[i];

		grp->total_faults -= p->total_numa_faults;



		list_del(&p->numa_entry);

		grp->nr_tasks--;

		spin_unlock(&grp->lock);

		spin_unlock_irq(&grp->lock);

		rcu_assign_pointer(p->numa_group, NULL);

		put_numa_group(grp);

	}

kernel/sched/sched.h

+9 −0
Original line number Diff line number Diff line
@@ -1385,6 +1385,15 @@ static inline void double_lock(spinlock_t *l1, spinlock_t *l2) 
	spin_lock_nested(l2, SINGLE_DEPTH_NESTING);

}



static inline void double_lock_irq(spinlock_t *l1, spinlock_t *l2)

{

	if (l1 > l2)

		swap(l1, l2);



	spin_lock_irq(l1);

	spin_lock_nested(l2, SINGLE_DEPTH_NESTING);

}



static inline void double_raw_lock(raw_spinlock_t *l1, raw_spinlock_t *l2)

{

	if (l1 > l2)

CRA Git | Maintained and supported by SUSTech CRA and CCSE