From 56cc81bb39cba1791c46c31de789ad370dde9fcd Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 5 Nov 2021 13:31:05 -0700 Subject: [PATCH] BACKPORT: 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 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 --- drivers/scsi/ufs/ufshcd.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 7f48823dd38a..d2fdd9f9097d 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -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;