From d56a3389b8685b71b01dde2f378cea05e2c8e231 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 2 Nov 2021 17:02:42 -0700 Subject: [PATCH] FROMLIST: scsi: ufs: Fix a deadlock in the error handler 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 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 --- drivers/scsi/ufs/ufshcd.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index b2b15c1d9c17..d593190f0fa8 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -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;