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sched/numa: Fix task_numa_free() lockdep splat

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

  156654f491 ("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: Sasha Levin <sasha.levin@oracle.com>
Fixes: 156654f491 ("sched/numa: Move task_numa_free() to __put_task_struct()")
Signed-off-by: Mike Galbraith <bitbucket@online.de>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mike Galbraith 2014-04-07 10:55:15 +02:00 committed by Ingo Molnar
parent 467cbd207a
commit 60e69eed85
2 changed files with 16 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
kernel/sched/fair.c
View file

@ -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);
}

9
kernel/sched/sched.h
View file

@ -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)