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Commit 38135535 authored by Subhash Jadavani's avatar Subhash Jadavani Committed by Martin K. Petersen
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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: default avatarSubhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: default avatarCan Guo <cang@codeaurora.org>
Signed-off-by: default avatarAsutosh Das <asutoshd@codeaurora.org>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent b334456e

drivers/scsi/ufs/ufshcd.c

+20 −8
Original line number Diff line number Diff line
@@ -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 @@ int ufshcd_hold(struct ufs_hba *hba, bool async) 
		 * 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 @@ static void ufshcd_err_handler(struct work_struct *work) 


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.

drivers/scsi/ufs/ufshcd.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */