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From: yangerkun <yangerkun@huaweicloud.com>
To: agk@redhat.com, snitzer@kernel.org, dm-devel@redhat.com
Cc: yangerkun@huawei.com, yangerkun@huaweicloud.com
Subject: [dm-devel] [PATCH] dm-crypt: fix softlockup in dmcrypt_write
Date: Thu, 23 Feb 2023 11:19:47 +0800	[thread overview]
Message-ID: <20230223031947.3717433-1-yangerkun@huaweicloud.com> (raw)

From: yangerkun <yangerkun@huawei.com>

We meet a softlockup:

localhost login: [ 3391.153255][   C12] watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [dmcrypt_write/2:2897]
...
[ 3391.258372][   C12] CPU: 12 PID: 2897 Comm: dmcrypt_write/2 Tainted: G             L    5.10.0+ #8
[ 3391.267288][   C12] Hardware name: Huawei TaiShan 2280 V2/BC82AMDDA, BIOS 1.75 04/26/2021
[ 3391.275428][   C12] pstate: 80400009 (Nzcv daif +PAN -UAO -TCO BTYPE=--)
[ 3391.282102][   C12] pc : blk_attempt_bio_merge.part.6+0x38/0x158
[ 3391.288080][   C12] lr : blk_attempt_plug_merge+0xc0/0x1b0
[ 3391.293540][   C12] sp : ffff8000718abc30
[ 3391.297530][   C12] x29: ffff8000718abc30 x28: 0000000000000000
[ 3391.303509][   C12] x27: ffff2020361d9ac0 x26: 0000000000000001
[ 3391.309488][   C12] x25: 0000000000000001 x24: ffff8000718abd08
[ 3391.315467][   C12] x23: ffff0020a10dbb00 x22: 0000000000000001
[ 3391.321445][   C12] x21: ffff8000718abe20 x20: ffff0020a10dbb00
[ 3391.327424][   C12] x19: ffff0020aed7b040 x18: 0000000000000000
[ 3391.333402][   C12] x17: 0000000000000000 x16: fffffdffffe00000
[ 3391.339381][   C12] x15: 0000000000001000 x14: 0000000000000000
[ 3391.345359][   C12] x13: 0000000000002000 x12: ffff2060011f9070
[ 3391.351338][   C12] x11: 0000000000000001 x10: 0000000000000002
[ 3391.357316][   C12] x9 : ffff800010586c38 x8 : ffff202009a7f200
[ 3391.363294][   C12] x7 : ffff8000718abd00 x6 : ffff20200df33750
[ 3391.369274][   C12] x5 : 0000000000000001 x4 : 0000000000000000
[ 3391.375252][   C12] x3 : 0000000000000001 x2 : ffff0020a10dbb00
[ 3391.381230][   C12] x1 : ffff0020aed7b040 x0 : 0000000000001000
[ 3391.387210][   C12] Call trace:
[ 3391.390338][   C12]  blk_attempt_bio_merge.part.6+0x38/0x158
[ 3391.395970][   C12]  blk_attempt_plug_merge+0xc0/0x1b0
[ 3391.401085][   C12]  blk_mq_submit_bio+0x398/0x550
[ 3391.405856][   C12]  submit_bio_noacct+0x308/0x380
[ 3391.410630][   C12]  dmcrypt_write+0x1e4/0x208 [dm_crypt]
[ 3391.416005][   C12]  kthread+0x130/0x138
[ 3391.419911][   C12]  ret_from_fork+0x10/0x18

dmcrypt_write may see not empty write_tree for a long time if we have a
heavy load of write, and submit_bio for high-performance disk like nvme
can always get a valid tag, so the bio routine will not yield cpu too.
So the softlockup seems reasonably.

Fix it by schedule periodically.

Fixes: dc2676210c42 ("dm crypt: offload writes to thread")
Signed-off-by: yangerkun <yangerkun@huawei.com>
---
 drivers/md/dm-crypt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 2653516bcdef..755a01d72cdb 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1891,6 +1891,7 @@ static int dmcrypt_write(void *data)
 {
 	struct crypt_config *cc = data;
 	struct dm_crypt_io *io;
+	unsigned long start_time = jiffies;
 
 	while (1) {
 		struct rb_root write_tree;
@@ -1913,6 +1914,7 @@ static int dmcrypt_write(void *data)
 
 		schedule();
 
+		start_time = jiffies;
 		set_current_state(TASK_RUNNING);
 		spin_lock_irq(&cc->write_thread_lock);
 		goto continue_locked;
@@ -1924,6 +1926,10 @@ static int dmcrypt_write(void *data)
 
 		BUG_ON(rb_parent(write_tree.rb_node));
 
+		if (time_is_before_jiffies(start_time + HZ)) {
+			schedule();
+			start_time = jiffies;
+		}
 		/*
 		 * Note: we cannot walk the tree here with rb_next because
 		 * the structures may be freed when kcryptd_io_write is called.
-- 
2.31.1

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             reply	other threads:[~2023-02-23  7:40 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-23  3:19 yangerkun [this message]
2023-02-26  2:01 ` [dm-devel] [PATCH] dm-crypt: fix softlockup in dmcrypt_write Bart Van Assche
2023-02-27  1:31   ` yangerkun
2023-02-27 17:55     ` [dm-devel] " Mike Snitzer
2023-02-27 18:03       ` Mike Snitzer
2023-02-27 18:06         ` Mike Snitzer
2023-02-28  1:40           ` yangerkun
2023-03-06 18:02             ` Mikulas Patocka
2023-03-06 18:16               ` Bart Van Assche
2023-03-06 19:03                 ` Mikulas Patocka
2023-02-28  1:25       ` yangerkun
2023-02-28  7:22         ` yangerkun

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