On 01/12/2021 01:33, Bart Van Assche wrote:
> 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@xxxxxxx>
Reviewed-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> ---
> 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 074ea9ae54e0..c4cf5c4b4893 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -2684,6 +2684,12 @@ 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;
> @@ -2762,7 +2768,10 @@ 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()) {
> @@ -5951,8 +5960,7 @@ 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);
> }
>
>
