From: He Zhe <zhe.he@windriver.com>
Date: Wed, 19 Dec 2018 16:30:57 +0100
Subject: kmemleak: Turn kmemleak_lock to raw spinlock on RT
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Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 5d1ead89781055e18003aba8f4a134160d947776
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

[ Upstream commit 41cf9e5bb14fbbf782e4191b792d3b898c130469 ]

kmemleak_lock, as a rwlock on RT, can possibly be held in atomic context and
causes the follow BUG.

BUG: scheduling while atomic: migration/15/132/0x00000002
Preemption disabled at:
[<ffffffff8c927c11>] cpu_stopper_thread+0x71/0x100
CPU: 15 PID: 132 Comm: migration/15 Not tainted 4.19.0-rt1-preempt-rt #1
Call Trace:
 schedule+0x3d/0xe0
 __rt_spin_lock+0x26/0x30
 __write_rt_lock+0x23/0x1a0
 rt_write_lock+0x2a/0x30
 find_and_remove_object+0x1e/0x80
 delete_object_full+0x10/0x20
 kmemleak_free+0x32/0x50
 kfree+0x104/0x1f0
 intel_pmu_cpu_dying+0x67/0x70
 x86_pmu_dying_cpu+0x1a/0x30
 cpuhp_invoke_callback+0x92/0x700
 take_cpu_down+0x70/0xa0
 multi_cpu_stop+0x62/0xc0
 cpu_stopper_thread+0x79/0x100
 smpboot_thread_fn+0x20f/0x2d0
 kthread+0x121/0x140

And on v4.18 stable tree the following call trace, caused by grabbing
kmemleak_lock again, is also observed.

kernel BUG at kernel/locking/rtmutex.c:1048!
CPU: 5 PID: 689 Comm: mkfs.ext4 Not tainted 4.18.16-rt9-preempt-rt #1
Call Trace:
 rt_write_lock+0x2a/0x30
 create_object+0x17d/0x2b0
 kmemleak_alloc+0x34/0x50
 kmem_cache_alloc+0x146/0x220
 mempool_alloc_slab+0x15/0x20
 mempool_alloc+0x65/0x170
 sg_pool_alloc+0x21/0x60
 sg_alloc_table_chained+0x8b/0xb0
…
 blk_flush_plug_list+0x204/0x230
 schedule+0x87/0xe0
 rt_write_lock+0x2a/0x30
 create_object+0x17d/0x2b0
 kmemleak_alloc+0x34/0x50
 __kmalloc_node+0x1cd/0x340
 alloc_request_size+0x30/0x70
 mempool_alloc+0x65/0x170
 get_request+0x4e3/0x8d0
 blk_queue_bio+0x153/0x470
 generic_make_request+0x1dc/0x3f0
 submit_bio+0x49/0x140
…

kmemleak is an error detecting feature. We would not expect as good performance
as without it. As there is no raw rwlock defining helpers, we turn kmemleak_lock
to a raw spinlock.

Signed-off-by: He Zhe <zhe.he@windriver.com>
Cc: catalin.marinas@arm.com
Cc: bigeasy@linutronix.de
Cc: tglx@linutronix.de
Cc: rostedt@goodmis.org
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lkml.kernel.org/r/1542877459-144382-1-git-send-email-zhe.he@windriver.com
Link: https://lkml.kernel.org/r/20181218150744.GB20197@arrakis.emea.arm.com
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 mm/kmemleak.c |   20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -26,7 +26,7 @@
  *
  * The following locks and mutexes are used by kmemleak:
  *
- * - kmemleak_lock (rwlock): protects the object_list modifications and
+ * - kmemleak_lock (raw spinlock): protects the object_list modifications and
  *   accesses to the object_tree_root. The object_list is the main list
  *   holding the metadata (struct kmemleak_object) for the allocated memory
  *   blocks. The object_tree_root is a red black tree used to look-up
@@ -199,7 +199,7 @@ static LIST_HEAD(gray_list);
 /* search tree for object boundaries */
 static struct rb_root object_tree_root = RB_ROOT;
 /* rw_lock protecting the access to object_list and object_tree_root */
-static DEFINE_RWLOCK(kmemleak_lock);
+static DEFINE_RAW_SPINLOCK(kmemleak_lock);
 
 /* allocation caches for kmemleak internal data */
 static struct kmem_cache *object_cache;
@@ -493,9 +493,9 @@ static struct kmemleak_object *find_and_
 	struct kmemleak_object *object;
 
 	rcu_read_lock();
-	read_lock_irqsave(&kmemleak_lock, flags);
+	raw_spin_lock_irqsave(&kmemleak_lock, flags);
 	object = lookup_object(ptr, alias);
-	read_unlock_irqrestore(&kmemleak_lock, flags);
+	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
 
 	/* check whether the object is still available */
 	if (object && !get_object(object))
@@ -515,13 +515,13 @@ static struct kmemleak_object *find_and_
 	unsigned long flags;
 	struct kmemleak_object *object;
 
-	write_lock_irqsave(&kmemleak_lock, flags);
+	raw_spin_lock_irqsave(&kmemleak_lock, flags);
 	object = lookup_object(ptr, alias);
 	if (object) {
 		rb_erase(&object->rb_node, &object_tree_root);
 		list_del_rcu(&object->object_list);
 	}
-	write_unlock_irqrestore(&kmemleak_lock, flags);
+	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
 
 	return object;
 }
@@ -595,7 +595,7 @@ static struct kmemleak_object *create_ob
 	/* kernel backtrace */
 	object->trace_len = __save_stack_trace(object->trace);
 
-	write_lock_irqsave(&kmemleak_lock, flags);
+	raw_spin_lock_irqsave(&kmemleak_lock, flags);
 
 	min_addr = min(min_addr, ptr);
 	max_addr = max(max_addr, ptr + size);
@@ -626,7 +626,7 @@ static struct kmemleak_object *create_ob
 
 	list_add_tail_rcu(&object->object_list, &object_list);
 out:
-	write_unlock_irqrestore(&kmemleak_lock, flags);
+	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
 	return object;
 }
 
@@ -1305,7 +1305,7 @@ static void scan_block(void *_start, voi
 	unsigned long *end = _end - (BYTES_PER_POINTER - 1);
 	unsigned long flags;
 
-	read_lock_irqsave(&kmemleak_lock, flags);
+	raw_spin_lock_irqsave(&kmemleak_lock, flags);
 	for (ptr = start; ptr < end; ptr++) {
 		struct kmemleak_object *object;
 		unsigned long pointer;
@@ -1367,7 +1367,7 @@ static void scan_block(void *_start, voi
 			spin_unlock(&object->lock);
 		}
 	}
-	read_unlock_irqrestore(&kmemleak_lock, flags);
+	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
 }
 
 /*