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From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 6 Apr 2010 16:51:31 +0200
Subject: md: raid5: Make raid5_percpu handling RT aware
__raid_run_ops() disables preemption with get_cpu() around the access
to the raid5_percpu variables. That causes scheduling while atomic
spews on RT.
Serialize the access to the percpu data with a lock and keep the code
preemptible.
Reported-by: Udo van den Heuvel <udovdh@xs4all.nl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Udo van den Heuvel <udovdh@xs4all.nl>
---
drivers/md/raid5.c | 7 +++++--
drivers/md/raid5.h | 1 +
2 files changed, 6 insertions(+), 2 deletions(-)
Index: linux-stable/drivers/md/raid5.c
===================================================================
--- linux-stable.orig/drivers/md/raid5.c
+++ linux-stable/drivers/md/raid5.c
@@ -1373,8 +1373,9 @@ static void __raid_run_ops(struct stripe
struct raid5_percpu *percpu;
unsigned long cpu;
- cpu = get_cpu();
+ cpu = get_cpu_light();
percpu = per_cpu_ptr(conf->percpu, cpu);
+ spin_lock(&percpu->lock);
if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
ops_run_biofill(sh);
overlap_clear++;
@@ -1426,7 +1427,8 @@ static void __raid_run_ops(struct stripe
if (test_and_clear_bit(R5_Overlap, &dev->flags))
wake_up(&sh->raid_conf->wait_for_overlap);
}
- put_cpu();
+ spin_unlock(&percpu->lock);
+ put_cpu_light();
}
#ifdef CONFIG_MULTICORE_RAID456
@@ -4925,6 +4927,7 @@ static int raid5_alloc_percpu(struct r5c
break;
}
per_cpu_ptr(conf->percpu, cpu)->scribble = scribble;
+ spin_lock_init(&per_cpu_ptr(conf->percpu, cpu)->lock);
}
#ifdef CONFIG_HOTPLUG_CPU
conf->cpu_notify.notifier_call = raid456_cpu_notify;
Index: linux-stable/drivers/md/raid5.h
===================================================================
--- linux-stable.orig/drivers/md/raid5.h
+++ linux-stable/drivers/md/raid5.h
@@ -427,6 +427,7 @@ struct r5conf {
int recovery_disabled;
/* per cpu variables */
struct raid5_percpu {
+ spinlock_t lock; /* Protection for -RT */
struct page *spare_page; /* Used when checking P/Q in raid6 */
void *scribble; /* space for constructing buffer
* lists and performing address
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