linux-kernel - [PATCH] lockdep: fix warning in case of no

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Date:	Wed, 13 Jul 2016 11:06:36 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ming Lei <tom.leiming@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: [PATCH] lockdep: fix warning in case of no_validate lock

Now there are several locks which are marked as
no_validate, so name of the lock class can be
different with the no_validate lock.

This patch avoids this warning for this case, and
fix the following warning:

[   14.413292] ------------[ cut here ]------------
[   14.413297] WARNING: CPU: 1 PID: 1434 at kernel/locking/lockdep.c:704
register_lock_class+0x44a/0x4f0
[   14.413298] Modules linked in: bcache raid1 psmouse dax_pmem dax nd_pmem
serio_raw nvme nd_btt nvme_core floppy null_blk configs autofs4
[   14.413309] CPU: 1 PID: 1434 Comm: bcache-register Tainted: G
W 4.7.0-rc6-next-20160708+ #2069
[   14.413310] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
rel-1.9.0-0-g01a84be-prebuilt.qemu-project.org 04/01/2014
[   14.413311]  0000000000000000 ffff880076973900 ffffffffba459dec 0000000000000000
[   14.413313]  0000000000000000 ffff880076973940 ffffffffba08af71 000002c0ba1312a2
[   14.413316]  ffffffffbb9fd1e0 0000000000000000 0000000000000000 ffff880074d078d0
[   14.413318] Call Trace:
[   14.413321]  [<ffffffffba459dec>] dump_stack+0x85/0xc9
[   14.413323]  [<ffffffffba08af71>] __warn+0xd1/0xf0
[   14.413324]  [<ffffffffba08b05d>] warn_slowpath_null+0x1d/0x20
[   14.413326]  [<ffffffffba0e5b8a>] register_lock_class+0x44a/0x4f0
[   14.413328]  [<ffffffffba0e81a5>] __lock_acquire+0x85/0x1920
[   14.413330]  [<ffffffffba06c893>] ? kvm_clock_read+0x23/0x40
[   14.413332]  [<ffffffffba03ebc9>] ? sched_clock+0x9/0x10
[   14.413334]  [<ffffffffba0c5568>] ? sched_clock_local+0x18/0x80
[   14.413336]  [<ffffffffba0ea0c4>] lock_acquire+0xd4/0x240
[   14.413342]  [<ffffffffc02f29b4>] ? mca_reap+0x54/0x180 [bcache]
[   14.413343]  [<ffffffffba0e3937>] down_write_trylock+0x67/0x80
[   14.413347]  [<ffffffffc02f29b4>] ? mca_reap+0x54/0x180 [bcache]
[   14.413351]  [<ffffffffc02f29b4>] mca_reap+0x54/0x180 [bcache]
[   14.413354]  [<ffffffffc02f2e62>] mca_alloc+0xc2/0x5a0 [bcache]
[   14.413358]  [<ffffffffc02f39f3>] bch_btree_node_get+0x143/0x290 [bcache]
[   14.413364]  [<ffffffffc0305939>] run_cache_set+0x239/0x8f0 [bcache]
[   14.413368]  [<ffffffffc0307c12>] register_bcache+0x14d2/0x1a30 [bcache]
[   14.413370]  [<ffffffffba80191b>] ? mutex_lock_nested+0x2db/0x460
[   14.413372]  [<ffffffffba45c52f>] kobj_attr_store+0xf/0x20
[   14.413374]  [<ffffffffba2f5f44>] sysfs_kf_write+0x44/0x60
[   14.413376]  [<ffffffffba2f54d4>] kernfs_fop_write+0x144/0x1e0
[   14.413378]  [<ffffffffba265728>] __vfs_write+0x28/0x120
[   14.413380]  [<ffffffffba0e3bd7>] ? percpu_down_read+0x57/0x90
[   14.413381]  [<ffffffffba26910a>] ? __sb_start_write+0xca/0xe0
[   14.413382]  [<ffffffffba26910a>] ? __sb_start_write+0xca/0xe0
[   14.413383]  [<ffffffffba265e35>] vfs_write+0xb5/0x1b0
[   14.413385]  [<ffffffffba0e7ccf>] ? trace_hardirqs_on_caller+0xef/0x210
[   14.413386]  [<ffffffffba2671c9>] SyS_write+0x49/0xa0
[   14.413388]  [<ffffffffba806ec0>] entry_SYSCALL_64_fastpath+0x23/0xc1
[   14.413391]  [<ffffffffba478c93>] ? __this_cpu_preempt_check+0x13/0x20
[   14.413392] ---[ end trace 16710c495b4dbf2f ]---

Signed-off-by: Ming Lei <tom.leiming@...il.com>
---
 kernel/locking/lockdep.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 589d763..cf071ec 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -701,7 +701,8 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 			 * Huh! same key, different name? Did someone trample
 			 * on some memory? We're most confused.
 			 */
-			WARN_ON_ONCE(class->name != lock->name);
+			WARN_ON_ONCE(lock->key != &__lockdep_no_validate__ &&
+					class->name != lock->name);
 			return class;
 		}
 	}
-- 
1.9.1