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.

Link: https://lore.kernel.org/r/20211203231950.193369-10-bvanassche@acm.org
Tested-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 2d0f594..da4714a 100644 (file)
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -128,8 +128,9 @@ EXPORT_SYMBOL_GPL(ufshcd_dump_regs);
 enum {
        UFSHCD_MAX_CHANNEL      = 0,
        UFSHCD_MAX_ID           = 1,
-       UFSHCD_CMD_PER_LUN      = 32,
-       UFSHCD_CAN_QUEUE        = 32,
+       UFSHCD_NUM_RESERVED     = 1,
+       UFSHCD_CMD_PER_LUN      = 32 - UFSHCD_NUM_RESERVED,
+       UFSHCD_CAN_QUEUE        = 32 - UFSHCD_NUM_RESERVED,
 };
 
 static const char *const ufshcd_state_name[] = {
@@ -2170,6 +2171,7 @@ static inline int ufshcd_hba_capabilities(struct ufs_hba *hba)
        hba->nutrs = (hba->capabilities & MASK_TRANSFER_REQUESTS_SLOTS) + 1;
        hba->nutmrs =
        ((hba->capabilities & MASK_TASK_MANAGEMENT_REQUEST_SLOTS) >> 16) + 1;
+       hba->reserved_slot = hba->nutrs - 1;
 
        /* Read crypto capabilities */
        err = ufshcd_hba_init_crypto_capabilities(hba);
@@ -2912,30 +2914,15 @@ static int ufshcd_wait_for_dev_cmd(struct ufs_hba *hba,
 static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
                enum dev_cmd_type cmd_type, int timeout)
 {
-       struct request_queue *q = hba->cmd_queue;
        DECLARE_COMPLETION_ONSTACK(wait);
-       struct request *req;
+       const u32 tag = hba->reserved_slot;
        struct ufshcd_lrb *lrbp;
        int err;
-       int tag;
 
-       down_read(&hba->clk_scaling_lock);
+       /* Protects use of hba->reserved_slot. */
+       lockdep_assert_held(&hba->dev_cmd.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_mq_alloc_request(q, REQ_OP_DRV_OUT, 0);
-       if (IS_ERR(req)) {
-               err = PTR_ERR(req);
-               goto out_unlock;
-       }
-       tag = req->tag;
-       WARN_ONCE(tag < 0, "Invalid tag %d\n", tag);
-       /* Set the timeout such that the SCSI error handler is not activated. */
-       req->timeout = msecs_to_jiffies(2 * timeout);
-       blk_mq_start_request(req);
+       down_read(&hba->clk_scaling_lock);
 
        lrbp = &hba->lrb[tag];
        WARN_ON(lrbp->cmd);
@@ -2953,8 +2940,6 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
                                    (struct utp_upiu_req *)lrbp->ucd_rsp_ptr);
 
 out:
-       blk_mq_free_request(req);
-out_unlock:
        up_read(&hba->clk_scaling_lock);
        return err;
 }
@@ -6689,23 +6674,16 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,
                                        enum dev_cmd_type cmd_type,
                                        enum query_opcode desc_op)
 {
-       struct request_queue *q = hba->cmd_queue;
        DECLARE_COMPLETION_ONSTACK(wait);
-       struct request *req;
+       const u32 tag = hba->reserved_slot;
        struct ufshcd_lrb *lrbp;
        int err = 0;
-       int tag;
        u8 upiu_flags;
 
-       down_read(&hba->clk_scaling_lock);
+       /* Protects use of hba->reserved_slot. */
+       lockdep_assert_held(&hba->dev_cmd.lock);
 
-       req = blk_mq_alloc_request(q, REQ_OP_DRV_OUT, 0);
-       if (IS_ERR(req)) {
-               err = PTR_ERR(req);
-               goto out_unlock;
-       }
-       tag = req->tag;
-       WARN_ONCE(tag < 0, "Invalid tag %d\n", tag);
+       down_read(&hba->clk_scaling_lock);
 
        lrbp = &hba->lrb[tag];
        WARN_ON(lrbp->cmd);
@@ -6774,9 +6752,6 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,
        ufshcd_add_query_upiu_trace(hba, err ? UFS_QUERY_ERR : UFS_QUERY_COMP,
                                    (struct utp_upiu_req *)lrbp->ucd_rsp_ptr);
 
-       blk_mq_free_request(req);
-
-out_unlock:
        up_read(&hba->clk_scaling_lock);
        return err;
 }
@@ -9507,8 +9482,8 @@ 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 - UFSHCD_NUM_RESERVED;
+       host->cmd_per_lun = hba->nutrs - UFSHCD_NUM_RESERVED;
        host->max_id = UFSHCD_MAX_ID;
        host->max_lun = UFS_MAX_LUNS;
        host->max_channel = UFSHCD_MAX_CHANNEL;

diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index ecc6c54..c3c2792 100644 (file)
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -745,6 +745,7 @@ struct ufs_hba_monitor {
  * @capabilities: UFS Controller Capabilities
  * @nutrs: Transfer Request Queue depth supported by controller
  * @nutmrs: Task Management Queue depth supported by controller
+ * @reserved_slot: Used to submit device commands. Protected by @dev_cmd.lock.
  * @ufs_version: UFS Version to which controller complies
  * @vops: pointer to variant specific operations
  * @priv: pointer to variant specific private data
@@ -836,6 +837,7 @@ struct ufs_hba {
        u32 capabilities;
        int nutrs;
        int nutmrs;
+       u32 reserved_slot;
        u32 ufs_version;
        const struct ufs_hba_variant_ops *vops;
        struct ufs_hba_variant_params *vps;