[PATCH v2 17/20] scsi: ufs: Stop using the clock scaling lock in the error handler

Bart Van Assche
2021-11-19T19:58:49Z

Instead of locking and unlocking the clock scaling lock, surround the
command queueing code with an RCU reader lock and call synchronize_rcu().
This patch prepares for removal of the clock scaling lock.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/ufs/ufshcd.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 6a743da7d2db..a6d3f71c6b00 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2702,6 +2702,12 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
if (!down_read_trylock(&hba->clk_scaling_lock))
return SCSI_MLQUEUE_HOST_BUSY;

+ /*
+ * Allows the UFS error handler to wait for prior ufshcd_queuecommand()
+ * calls.
+ */
+ rcu_read_lock();
+
switch (hba->ufshcd_state) {
case UFSHCD_STATE_OPERATIONAL:
break;
@@ -2780,7 +2786,10 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
}

ufshcd_send_command(hba, tag);
+
out:
+ rcu_read_unlock();
+
up_read(&hba->clk_scaling_lock);

if (ufs_trigger_eh()) {
@@ -5986,8 +5995,7 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
}
ufshcd_scsi_block_requests(hba);
/* Drain ufshcd_queuecommand() */
- down_write(&hba->clk_scaling_lock);
- up_write(&hba->clk_scaling_lock);
+ synchronize_rcu();
cancel_work_sync(&hba->eeh_work);
}