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Date: Sun, 02 Nov 2014 08:30:51 +0100 From: Mike Galbraith <umgwanakikbuti@...il.com> To: Steven Rostedt <rostedt@...dmis.org> Cc: LKML <linux-kernel@...r.kernel.org>, linux-rt-users <linux-rt-users@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Carsten Emde <C.Emde@...dl.org>, John Kacur <jkacur@...hat.com>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Clark Williams <williams@...hat.com> Subject: 3.14.23-rt20 - sched/numa: Fix task_numa_free() lockdep splat >From 60e69eed85bb7b5198ef70643b5895c26ad76ef7 Mon Sep 17 00:00:00 2001 From: Mike Galbraith <bitbucket@...ine.de> Date: Mon, 7 Apr 2014 10:55:15 +0200 Subject: 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. Reported-by: Sasha Levin <sasha.levin@...cle.com> Fixes: 156654f491dd ("sched/numa: Move task_numa_free() to __put_task_struct()") Signed-off-by: Mike Galbraith <bitbucket@...ine.de> Signed-off-by: Peter Zijlstra <peterz@...radead.org> Cc: torvalds@...ux-foundation.org Cc: mgorman@...e.com Cc: akpm@...ux-foundation.org Cc: Dave Jones <davej@...hat.com> Link: http://lkml.kernel.org/r/1396860915.5170.5.camel@marge.simpson.net Signed-off-by: Ingo Molnar <mingo@...nel.org> --- 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 @@ -1402,6 +1402,15 @@ 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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