Re: [PATCH] scsi: ufs: core: fix devfreq deadlocks

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On 12/22/22 02:21, Johan Hovold wrote:
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index bda61be5f035..5c3821b2fcf8 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -1234,12 +1234,14 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
  	 * clock scaling is in progress
  	 */
  	ufshcd_scsi_block_requests(hba);
+	mutex_lock(&hba->wb_mutex);
  	down_write(&hba->clk_scaling_lock);
if (!hba->clk_scaling.is_allowed ||
  	    ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
  		ret = -EBUSY;
  		up_write(&hba->clk_scaling_lock);
+		mutex_unlock(&hba->wb_mutex);
  		ufshcd_scsi_unblock_requests(hba);
  		goto out;
  	}
@@ -1251,12 +1253,16 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
  	return ret;
  }

Please add an __acquires(&hba->wb_mutex) annotation for sparse.

-static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock)
+static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool scale_up)
  {
-	if (writelock)
-		up_write(&hba->clk_scaling_lock);
-	else
-		up_read(&hba->clk_scaling_lock);
+	up_write(&hba->clk_scaling_lock);
+
+	/* Enable Write Booster if we have scaled up else disable it */
+	if (ufshcd_enable_wb_if_scaling_up(hba))
+		ufshcd_wb_toggle(hba, scale_up);
+
+	mutex_unlock(&hba->wb_mutex);
+
  	ufshcd_scsi_unblock_requests(hba);
  	ufshcd_release(hba);
  }

Please add a __releases(&hba->wb_mutex) annotation for sparse.

@@ -1273,7 +1279,6 @@ static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock)
  static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
  {
  	int ret = 0;
-	bool is_writelock = true;
ret = ufshcd_clock_scaling_prepare(hba);
  	if (ret)
@@ -1302,15 +1307,8 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
  		}
  	}
- /* Enable Write Booster if we have scaled up else disable it */
-	if (ufshcd_enable_wb_if_scaling_up(hba)) {
-		downgrade_write(&hba->clk_scaling_lock);
-		is_writelock = false;
-		ufshcd_wb_toggle(hba, scale_up);
-	}
-
  out_unprepare:
-	ufshcd_clock_scaling_unprepare(hba, is_writelock);
+	ufshcd_clock_scaling_unprepare(hba, scale_up);
  	return ret;
  }

This patch moves the ufshcd_wb_toggle() from before the out_unprepare label to after the out_unprepare label (into ufshcd_clock_scaling_unprepare()). Does this change perhaps introduce a new call to ufshcd_wb_toggle() in error paths?

Thanks,

Bart.




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