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From:   Clark Williams <williams@redhat.com>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org
Subject: [PATCH RT] rt: convert mm/kasan/quarantine_lock to raw_spinlock
Date:   Tue, 18 Sep 2018 10:29:31 -0500
Message-Id: <20180918152931.17322-1-williams@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The static lock quarantine_lock is used in mm/kasan/quarantine.c to protect
the quarantine queue datastructures. It is taken inside quarantine queue
manipulation routines (quarantine_put(), quarantine_reduce() and quarantine_remove_cache()),
with IRQs disabled. This is no problem on a stock kernel but is problematic
on an RT kernel where spin locks are converted to rt_mutex_t, which can sleep.

Convert the quarantine_lock to a raw spinlock. The usage of quarantine_lock
is confined to quarantine.c and the work performed while the lock is held is limited.

Signed-off-by: Clark Williams <williams@redhat.com>
---
 mm/kasan/quarantine.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 3a8ddf8baf7d..b209dbaefde8 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -103,7 +103,7 @@ static int quarantine_head;
 static int quarantine_tail;
 /* Total size of all objects in global_quarantine across all batches. */
 static unsigned long quarantine_size;
-static DEFINE_SPINLOCK(quarantine_lock);
+static DEFINE_RAW_SPINLOCK(quarantine_lock);
 DEFINE_STATIC_SRCU(remove_cache_srcu);
 
 /* Maximum size of the global queue. */
@@ -190,7 +190,7 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
 	if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
 		qlist_move_all(q, &temp);
 
-		spin_lock(&quarantine_lock);
+		raw_spin_lock(&quarantine_lock);
 		WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes);
 		qlist_move_all(&temp, &global_quarantine[quarantine_tail]);
 		if (global_quarantine[quarantine_tail].bytes >=
@@ -203,7 +203,7 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
 			if (new_tail != quarantine_head)
 				quarantine_tail = new_tail;
 		}
-		spin_unlock(&quarantine_lock);
+		raw_spin_unlock(&quarantine_lock);
 	}
 
 	local_irq_restore(flags);
@@ -230,7 +230,7 @@ void quarantine_reduce(void)
 	 * expected case).
 	 */
 	srcu_idx = srcu_read_lock(&remove_cache_srcu);
-	spin_lock_irqsave(&quarantine_lock, flags);
+	raw_spin_lock_irqsave(&quarantine_lock, flags);
 
 	/*
 	 * Update quarantine size in case of hotplug. Allocate a fraction of
@@ -254,7 +254,7 @@ void quarantine_reduce(void)
 			quarantine_head = 0;
 	}
 
-	spin_unlock_irqrestore(&quarantine_lock, flags);
+	raw_spin_unlock_irqrestore(&quarantine_lock, flags);
 
 	qlist_free_all(&to_free, NULL);
 	srcu_read_unlock(&remove_cache_srcu, srcu_idx);
@@ -310,17 +310,17 @@ void quarantine_remove_cache(struct kmem_cache *cache)
 	 */
 	on_each_cpu(per_cpu_remove_cache, cache, 1);
 
-	spin_lock_irqsave(&quarantine_lock, flags);
+	raw_spin_lock_irqsave(&quarantine_lock, flags);
 	for (i = 0; i < QUARANTINE_BATCHES; i++) {
 		if (qlist_empty(&global_quarantine[i]))
 			continue;
 		qlist_move_cache(&global_quarantine[i], &to_free, cache);
 		/* Scanning whole quarantine can take a while. */
-		spin_unlock_irqrestore(&quarantine_lock, flags);
+		raw_spin_unlock_irqrestore(&quarantine_lock, flags);
 		cond_resched();
-		spin_lock_irqsave(&quarantine_lock, flags);
+		raw_spin_lock_irqsave(&quarantine_lock, flags);
 	}
-	spin_unlock_irqrestore(&quarantine_lock, flags);
+	raw_spin_unlock_irqrestore(&quarantine_lock, flags);
 
 	qlist_free_all(&to_free, cache);
 
-- 
2.17.1