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From: David Decotigny <decot+git@google.com>
To: linux-kernel@vger.kernel.org
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	 Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org,
	 David Decotigny <ddecotig@google.com>
Subject: [PATCH RFC v2 1/1] mtd_blkdevs: avoid soft lockups with some mtd/spi devices
Date: Wed, 26 Jan 2022 01:21:34 -0800	[thread overview]
Message-ID: <20220126092134.579618-1-decot+git@google.com> (raw)

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 --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);
 	}
 }
-- 
2.35.0.rc0.227.g00780c9af4-goog


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WARNING: multiple messages have this Message-ID (diff)
From: David Decotigny <decot+git@google.com>
To: linux-kernel@vger.kernel.org
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org,
	David Decotigny <ddecotig@google.com>
Subject: [PATCH RFC v2 1/1] mtd_blkdevs: avoid soft lockups with some mtd/spi devices
Date: Wed, 26 Jan 2022 01:21:34 -0800	[thread overview]
Message-ID: <20220126092134.579618-1-decot+git@google.com> (raw)

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 --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);
 	}
 }
-- 
2.35.0.rc0.227.g00780c9af4-goog


             reply	other threads:[~2022-01-26  9:25 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-26  9:21 David Decotigny [this message]
2022-01-26  9:21 ` [PATCH RFC v2 1/1] mtd_blkdevs: avoid soft lockups with some mtd/spi devices David Decotigny

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