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BACKPORT: FROMLIST: scsi: ufs: Fix a deadlock in the error handler

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The following deadlock has been observed on a test setup:
* All tags allocated.
* The SCSI error handler calls ufshcd_eh_host_reset_handler()
* ufshcd_eh_host_reset_handler() queues work that calls ufshcd_err_handler()
* ufshcd_err_handler() locks up as follows:

Workqueue: ufs_eh_wq_0 ufshcd_err_handler.cfi_jt
Call trace:
 __switch_to+0x298/0x5d8
 __schedule+0x6cc/0xa94
 schedule+0x12c/0x298
 blk_mq_get_tag+0x210/0x480
 __blk_mq_alloc_request+0x1c8/0x284
 blk_get_request+0x74/0x134
 ufshcd_exec_dev_cmd+0x68/0x640
 ufshcd_verify_dev_init+0x68/0x35c
 ufshcd_probe_hba+0x12c/0x1cb8
 ufshcd_host_reset_and_restore+0x88/0x254
 ufshcd_reset_and_restore+0xd0/0x354
 ufshcd_err_handler+0x408/0xc58
 process_one_work+0x24c/0x66c
 worker_thread+0x3e8/0xa4c
 kthread+0x150/0x1b4
 ret_from_fork+0x10/0x30

Fix this lockup by making ufshcd_exec_dev_cmd() allocate a reserved
request.

This patch is closely related to the upstream patch with the same title.

Bug: 205080886
Link: https://lore.kernel.org/linux-scsi/700f0463-23a9-8465-f712-1188cb884dea@acm.org/T/#u
Change-Id: I9e9ba3f45ba23ecf576380aa19701d3437af6cdd
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Bart Van Assche
2021-11-05 13:31:05 -07:00
parent ff748ee298
commit 56cc81bb39
1 changed files with 1 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/scsi/ufs/ufshcd.c
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@@ -2932,12 +2932,7 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
down_read(&hba->clk_scaling_lock);
/*
* Get free slot, sleep if slots are unavailable.
* Even though we use wait_event() which sleeps indefinitely,
* the maximum wait time is bounded by SCSI request timeout.
*/
req = blk_get_request(q, REQ_OP_DRV_OUT, 0);
req = blk_mq_alloc_request(q, REQ_OP_DRV_OUT, BLK_MQ_REQ_RESERVED);
if (IS_ERR(req)) {
err = PTR_ERR(req);
goto out_unlock;