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-rw-r--r--features/rt/md-raid5-Make-raid5_percpu-handling-RT-aware.patch68
1 files changed, 68 insertions, 0 deletions
diff --git a/features/rt/md-raid5-Make-raid5_percpu-handling-RT-aware.patch b/features/rt/md-raid5-Make-raid5_percpu-handling-RT-aware.patch
new file mode 100644
index 00000000..43380924
--- /dev/null
+++ b/features/rt/md-raid5-Make-raid5_percpu-handling-RT-aware.patch
@@ -0,0 +1,68 @@
+From 28893cffb6465718d2196b201ec4dc9e41aca776 Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Tue, 6 Apr 2010 16:51:31 +0200
+Subject: [PATCH 135/191] 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(-)
+
+diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
+index 5d57a5bd171f..86d6a676a509 100644
+--- a/drivers/md/raid5.c
++++ b/drivers/md/raid5.c
+@@ -2216,8 +2216,9 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
+ 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_head *sh, unsigned long ops_request)
+ 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)
+@@ -7079,6 +7081,7 @@ static int raid456_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
+ __func__, cpu);
+ return -ENOMEM;
+ }
++ spin_lock_init(&per_cpu_ptr(conf->percpu, cpu)->lock);
+ return 0;
+ }
+
+diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
+index 5c05acf20e1f..665fe138ab4f 100644
+--- 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
+--
+2.19.1
+