On Sat, 17 May 2014 05:36:59 +0200
Mike Galbraith <umgwanakikbuti@xxxxxxxxx> wrote:
> 3.14-rt being build with a non-rt config is unlikely, but..
>
> >From 60e69eed85bb7b5198ef70643b5895c26ad76ef7 Mon Sep 17 00:00:00 2001
> From: Mike Galbraith <bitbucket@xxxxxxxxx>
> Date: Mon, 7 Apr 2014 10:55:15 +0200
> Subject: [PATCH] sched/numa: Fix task_numa_free() lockdep splat
>
> Sasha reported that lockdep claims that the following commit:
> made numa_group.lock interrupt unsafe:
>
> 156654f491dd ("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.
As I couldn't find a location, but Peter was able to point one out. You
actually did move it from a irq enabled region to a irq disabled region
(just not disabled most of the time).
Anyway, for inclusion into -rt...
Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
-- Steve
>
> Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> Fixes: 156654f491dd ("sched/numa: Move task_numa_free() to __put_task_struct()")
> Signed-off-by: Mike Galbraith <bitbucket@xxxxxxxxx>
> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
> Cc: mgorman@xxxxxxxx
> Cc: akpm@xxxxxxxxxxxxxxxxxxxx
> Cc: Dave Jones <davej@xxxxxxxxxx>
> Link: http://lkml.kernel.org/r/1396860915.5170.5.camel@xxxxxxxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
>
> ---
> kernel/sched/fair.c | 13 +++++++------
> kernel/sched/sched.h | 9 +++++++++
> 2 files changed, 16 insertions(+), 6 deletions(-)
>
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1371,7 +1371,7 @@ static void task_numa_placement(struct t
> /* 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 */
> @@ -1432,7 +1432,7 @@ static void task_numa_placement(struct t
> }
> }
>
> - spin_unlock(group_lock);
> + spin_unlock_irq(group_lock);
> }
>
> /* Preferred node as the node with the most faults */
> @@ -1532,7 +1532,8 @@ static void task_numa_group(struct task_
> 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 < 2*nr_node_ids; i++) {
> my_grp->faults[i] -= p->numa_faults[i];
> @@ -1546,7 +1547,7 @@ static void task_numa_group(struct task_
> grp->nr_tasks++;
>
> spin_unlock(&my_grp->lock);
> - spin_unlock(&grp->lock);
> + spin_unlock_irq(&grp->lock);
>
> rcu_assign_pointer(p->numa_group, grp);
>
> @@ -1565,14 +1566,14 @@ void task_numa_free(struct task_struct *
> void *numa_faults = p->numa_faults;
>
> if (grp) {
> - spin_lock(&grp->lock);
> + spin_lock_irq(&grp->lock);
> for (i = 0; i < 2*nr_node_ids; i++)
> grp->faults[i] -= p->numa_faults[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);
> }
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1392,6 +1392,15 @@ static inline void double_lock(spinlock_
> 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)
>
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