linux-kernel - [PATCH v3 1/5] scsi: ufs: atomic update for clkgating

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Message-Id: <20201024150646.1790529-2-jaegeuk@kernel.org>
Date:   Sat, 24 Oct 2020 08:06:42 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com
Cc:     cang@...eaurora.org, alim.akhtar@...sung.com, avri.altman@....com,
        bvanassche@....org, Jaegeuk Kim <jaegeuk@...gle.com>
Subject: [PATCH v3 1/5] 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.

If we use __ufshcd_release(), I've seen that gate_work can be called in parallel
with ungate_work, which results in UFS timeout when doing hibern8.
Should avoid it.

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 b8f573a02713..e0b479f9eb8a 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1807,19 +1807,19 @@ 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;
 }
 
-- 
2.29.0.rc1.297.gfa9743e501-goog