linux-kernel - [PATCH] scsi: ufs: core: Do not hold any lock in ufshcd_hba

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Message-Id: <20241124110747.206651-1-avri.altman@wdc.com>
Date: Sun, 24 Nov 2024 13:07:47 +0200
From: Avri Altman <avri.altman@....com>
To: "Martin K . Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bart Van Assche <bvanassche@....org>,
	Avri Altman <avri.altman@....com>
Subject: [PATCH] scsi: ufs: core: Do not hold any lock in ufshcd_hba_stop

This change is motivated by Bart's suggestion in [1], which enables to
further reduce the scsi host lock usage in the ufs driver. The reason
why it make sense, because although the legacy interrupt is disabled by
some but not all ufshcd_hba_stop() callers, it is safe to nest
disable_irq() calls as it checks the irq depth.

[1] https://lore.kernel.org/linux-scsi/c58e4fce-0a74-4469-ad16-f1edbd670728@acm.org/

Suggested-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: Avri Altman <avri.altman@....com>
---
 drivers/ufs/core/ufshcd.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index acc3607bbd9c..09a5ff49da5a 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -4811,16 +4811,11 @@ EXPORT_SYMBOL_GPL(ufshcd_make_hba_operational);
  */
 void ufshcd_hba_stop(struct ufs_hba *hba)
 {
-	unsigned long flags;
 	int err;
 
-	/*
-	 * Obtain the host lock to prevent that the controller is disabled
-	 * while the UFS interrupt handler is active on another CPU.
-	 */
-	spin_lock_irqsave(hba->host->host_lock, flags);
+	ufshcd_disable_irq(hba);
 	ufshcd_writel(hba, CONTROLLER_DISABLE,  REG_CONTROLLER_ENABLE);
-	spin_unlock_irqrestore(hba->host->host_lock, flags);
+	ufshcd_enable_irq(hba);
 
 	err = ufshcd_wait_for_register(hba, REG_CONTROLLER_ENABLE,
 					CONTROLLER_ENABLE, CONTROLLER_DISABLE,
-- 
2.25.1