diff mbox series

[RFC,v2,1/1] mtd_blkdevs: avoid soft lockups with some mtd/spi devices

Message ID 20220126092134.579618-1-decot+git@google.com
State Superseded
Delegated to: Miquel Raynal
Headers show
Series [RFC,v2,1/1] mtd_blkdevs: avoid soft lockups with some mtd/spi devices | expand

Commit Message

David Decotigny Jan. 26, 2022, 9:21 a.m. UTC 
From: David Decotigny <ddecotig@google.com>

With some spi devices, the heavy cpu usage due to polling the spi
registers may lead to netdev timeouts, RCU complaints, etc. This can
be acute in the absence of CONFIG_PREEMPT. This patch allows to give
enough breathing room to avoid those false positives.

Example splat on 5.10.92:
[  828.399306] rcu: INFO: rcu_sched self-detected stall on CPU
...
[  828.419245] Task dump for CPU 1:
[  828.422465] task:kworker/1:1H    state:R  running task on cpu   1   stack:    0 pid:   76 ppid:     2 flags:0x0000002a
[  828.433132] Workqueue: kblockd blk_mq_run_work_fn
[  828.437820] Call trace:
...
[  828.512267]  spi_mem_exec_op+0x4d0/0xde0
[  828.516184]  spi_mem_dirmap_read+0x180/0x39c
[  828.520443]  spi_nor_read_data+0x428/0x7e8
[  828.524523]  spi_nor_read+0x154/0x214
[  828.528172]  mtd_read_oob+0x440/0x714
[  828.531815]  mtd_read+0xac/0x120
[  828.535030]  mtdblock_readsect+0x178/0x230
[  828.539102]  mtd_blktrans_work+0x9fc/0xf28
[  828.543177]  mtd_queue_rq+0x1ac/0x2e4
[  828.546827]  blk_mq_dispatch_rq_list+0x2cc/0xa44
[  828.551419]  blk_mq_do_dispatch_sched+0xb0/0x7cc
[  828.556010]  __blk_mq_sched_dispatch_requests+0x350/0x494
[  828.561372]  blk_mq_sched_dispatch_requests+0xac/0xe4
[  828.566387]  __blk_mq_run_hw_queue+0x130/0x254
[  828.570806]  blk_mq_run_work_fn+0x50/0x60
[  828.574814]  process_one_work+0x578/0xf1c
[  828.578814]  worker_thread+0x5dc/0xea0
[  828.582547]  kthread+0x270/0x2d4
[  828.585765]  ret_from_fork+0x10/0x30


Signed-off-by: David Decotigny <ddecotig@google.com>
---
 drivers/mtd/mtd_blkdevs.c | 1 +
 1 file changed, 1 insertion(+)
diff mbox series

Patch

diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index 243f28a3206b4..64d2b093f114b 100644
--- a/drivers/mtd/mtd_blkdevs.c
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -158,6 +158,7 @@  static void mtd_blktrans_work(struct mtd_blktrans_dev *dev)
 		}
 
 		background_done = 0;
+		cond_resched();
 		spin_lock_irq(&dev->queue_lock);
 	}
 }