From 38135535dcc25af856336fda31aeef79d8ad9dab Mon Sep 17 00:00:00 2001 From: Subhash Jadavani Date: Thu, 3 May 2018 16:37:18 +0530 Subject: [PATCH] scsi: ufs: add reference counting for scsi block requests Currently we call the scsi_block_requests()/scsi_unblock_requests() whenever we want to block/unblock scsi requests but as there is no reference counting, nesting of these calls could leave us in undesired state sometime. Consider following call flow sequence: 1. func1() calls scsi_block_requests() but calls func2() before calling scsi_unblock_requests() 2. func2() calls scsi_block_requests() 3. func2() calls scsi_unblock_requests() 4. func1() calls scsi_unblock_requests() As there is no reference counting, we will have scsi requests unblocked after #3 instead of it to be unblocked only after #4. Though we may not have failures seen with this, we might run into some failures in future. Better solution would be to fix this by adding reference counting. Signed-off-by: Subhash Jadavani Signed-off-by: Can Guo Signed-off-by: Asutosh Das Signed-off-by: Martin K. Petersen --- drivers/scsi/ufs/ufshcd.c | 28 ++++++++++++++++++++-------- drivers/scsi/ufs/ufshcd.h | 2 ++ 2 files changed, 22 insertions(+), 8 deletions(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 79591934ef45..2859f6395eea 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -264,6 +264,18 @@ static inline void ufshcd_disable_irq(struct ufs_hba *hba) } } +static void ufshcd_scsi_unblock_requests(struct ufs_hba *hba) +{ + if (atomic_dec_and_test(&hba->scsi_block_reqs_cnt)) + scsi_unblock_requests(hba->host); +} + +static void ufshcd_scsi_block_requests(struct ufs_hba *hba) +{ + if (atomic_inc_return(&hba->scsi_block_reqs_cnt) == 1) + scsi_block_requests(hba->host); +} + /* replace non-printable or non-ASCII characters with spaces */ static inline void ufshcd_remove_non_printable(char *val) { @@ -1074,12 +1086,12 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba) * make sure that there are no outstanding requests when * clock scaling is in progress */ - scsi_block_requests(hba->host); + ufshcd_scsi_block_requests(hba); down_write(&hba->clk_scaling_lock); if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) { ret = -EBUSY; up_write(&hba->clk_scaling_lock); - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); } return ret; @@ -1088,7 +1100,7 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba) static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba) { up_write(&hba->clk_scaling_lock); - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); } /** @@ -1460,7 +1472,7 @@ static void ufshcd_ungate_work(struct work_struct *work) hba->clk_gating.is_suspended = false; } unblock_reqs: - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); } /** @@ -1516,7 +1528,7 @@ start: * work and to enable clocks. */ case CLKS_OFF: - scsi_block_requests(hba->host); + ufshcd_scsi_block_requests(hba); hba->clk_gating.state = REQ_CLKS_ON; trace_ufshcd_clk_gating(dev_name(hba->dev), hba->clk_gating.state); @@ -5298,7 +5310,7 @@ skip_err_handling: out: spin_unlock_irqrestore(hba->host->host_lock, flags); - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); ufshcd_release(hba); pm_runtime_put_sync(hba->dev); } @@ -5400,7 +5412,7 @@ static void ufshcd_check_errors(struct ufs_hba *hba) /* handle fatal errors only when link is functional */ if (hba->ufshcd_state == UFSHCD_STATE_OPERATIONAL) { /* block commands from scsi mid-layer */ - scsi_block_requests(hba->host); + ufshcd_scsi_block_requests(hba); hba->ufshcd_state = UFSHCD_STATE_EH_SCHEDULED; @@ -8032,7 +8044,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq) /* Hold auto suspend until async scan completes */ pm_runtime_get_sync(dev); - + atomic_set(&hba->scsi_block_reqs_cnt, 0); /* * We are assuming that device wasn't put in sleep/power-down * state exclusively during the boot stage before kernel. diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h index 53121fd6c287..a44b9f45ddd2 100644 --- a/drivers/scsi/ufs/ufshcd.h +++ b/drivers/scsi/ufs/ufshcd.h @@ -499,6 +499,7 @@ struct ufs_stats { * @urgent_bkops_lvl: keeps track of urgent bkops level for device * @is_urgent_bkops_lvl_checked: keeps track if the urgent bkops level for * device is known or not. + * @scsi_block_reqs_cnt: reference counting for scsi block requests */ struct ufs_hba { void __iomem *mmio_base; @@ -699,6 +700,7 @@ struct ufs_hba { struct rw_semaphore clk_scaling_lock; struct ufs_desc_size desc_size; + atomic_t scsi_block_reqs_cnt; }; /* Returns true if clocks can be gated. Otherwise false */ -- 2.39.5