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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
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.17-rt32.tar.xz
__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(-)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2216,8 +2216,9 @@ static void raid_run_ops(struct stripe_h
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++;
@@ -2276,7 +2277,8 @@ static void raid_run_ops(struct stripe_h
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();
}
static void free_stripe(struct kmem_cache *sc, struct stripe_head *sh)
@@ -7098,6 +7100,7 @@ static int raid456_cpu_up_prepare(unsign
__func__, cpu);
return -ENOMEM;
}
+ spin_lock_init(&per_cpu_ptr(conf->percpu, cpu)->lock);
return 0;
}
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -635,6 +635,7 @@ 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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