From: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
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 <subhashj@xxxxxxxxxxxxxx>
Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
---
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 dfeb194..c35a076 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)
{
@@ -1077,12 +1089,12 @@ 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;
@@ -1091,7 +1103,7 @@ 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);
}
/**
@@ -1411,7 +1423,7 @@ 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);
}
/**
@@ -1467,7 +1479,7 @@ 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);
@@ -5192,7 +5204,7 @@ 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);
}
@@ -5294,7 +5306,7 @@ 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;
@@ -8017,7 +8029,7 @@ 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 0417c42..76c31d5 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -498,6 +498,7 @@ 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;
@@ -698,6 +699,7 @@ 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 */
--
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Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
