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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 applies the remaining changes of the patch referred
to in the Link: field.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Bug: 204762899
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
2021-11-02 17:02:42 -07:00
committed by Todd Kjos
parent 77c166b207
commit d56a3389b8
1 changed files with 5 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
drivers/scsi/ufs/ufshcd.c
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@@ -2959,12 +2959,7 @@ 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;
@@ -8175,7 +8170,8 @@ static struct scsi_host_template ufshcd_driver_template = {
.this_id = -1,
.sg_tablesize = SG_ALL,
.cmd_per_lun = UFSHCD_CMD_PER_LUN,
.can_queue = UFSHCD_CAN_QUEUE,
.can_queue = UFSHCD_CAN_QUEUE - 1,
.reserved_tags = 1,
.max_segment_size = PRDT_DATA_BYTE_COUNT_MAX,
.max_host_blocked = 1,
.track_queue_depth = 1,
@@ -9532,8 +9528,8 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
/* Configure LRB */
ufshcd_host_memory_configure(hba);
host->can_queue = hba->nutrs;
host->cmd_per_lun = hba->nutrs;
host->can_queue = hba->nutrs - 1;
host->cmd_per_lun = hba->nutrs - 1;
host->max_id = UFSHCD_MAX_ID;
host->max_lun = UFS_MAX_LUNS;
host->max_channel = UFSHCD_MAX_CHANNEL;