linux-kernel - [PATCH 1/6] scsi: ufs: atomic update for clkgating

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Message-Id: <20200915204532.1672300-1-jaegeuk@kernel.org>
Date:   Tue, 15 Sep 2020 13:45:27 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com
Cc:     Jaegeuk Kim <jaegeuk@...gle.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>
Subject: [PATCH 1/6] scsi: ufs: atomic update for clkgating_enable

From: Jaegeuk Kim <jaegeuk@...gle.com>

When giving a stress test which enables/disables clkgating, we hit device
timeout sometimes. This patch avoids subtle racy condition to address it.

Cc: Alim Akhtar <alim.akhtar@...sung.com>
Cc: Avri Altman <avri.altman@....com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...gle.com>
---
 drivers/scsi/ufs/ufshcd.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 1d157ff58d817..d929c3d1e58cc 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1791,19 +1791,19 @@ static ssize_t ufshcd_clkgate_enable_store(struct device *dev,
 		return -EINVAL;
 
 	value = !!value;
+
+	spin_lock_irqsave(hba->host->host_lock, flags);
 	if (value == hba->clk_gating.is_enabled)
 		goto out;
 
-	if (value) {
-		ufshcd_release(hba);
-	} else {
-		spin_lock_irqsave(hba->host->host_lock, flags);
+	if (value)
+		hba->clk_gating.active_reqs--;
+	else
 		hba->clk_gating.active_reqs++;
-		spin_unlock_irqrestore(hba->host->host_lock, flags);
-	}
 
 	hba->clk_gating.is_enabled = value;
 out:
+	spin_unlock_irqrestore(hba->host->host_lock, flags);
 	return count;
 }
 
-- 
2.28.0.618.gf4bc123cb7-goog