linux-kernel - [PATCH v9 5/7] scsi: ufs: Fix ufshcd_hold() caused scheduling while atomic

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Date:   Mon, 10 Feb 2020 18:37:47 -0800
From:   Can Guo <cang@...eaurora.org>
To:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com, cang@...eaurora.org
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Subhash Jadavani <subhashj@...eaurora.org>,
        Bean Huo <beanhuo@...ron.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bart Van Assche <bvanassche@....org>,
        Tomas Winkler <tomas.winkler@...el.com>,
        linux-kernel@...r.kernel.org (open list),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/Mediatek SoC
        support),
        linux-mediatek@...ts.infradead.org (moderated list:ARM/Mediatek SoC
        support)
Subject: [PATCH v9 5/7] scsi: ufs: Fix ufshcd_hold() caused scheduling while atomic

The async version of ufshcd_hold(async == true), which is only called
in queuecommand path as for now, is expected to work in atomic context,
thus it should not sleep or schedule out. When it runs into the condition
that clocks are ON but link is still in hibern8 state, it should bail out
without flushing the clock ungate work.

Fixes: f2a785ac2312 ("scsi: ufshcd: Fix race between clk scaling and ungate work")
Signed-off-by: Can Guo <cang@...eaurora.org>
Reviewed-by: Hongwu Su <hongwus@...eaurora.org>
Reviewed-by: Asutosh Das <asutoshd@...eaurora.org>
Reviewed-by: Bean Huo <beanhuo@...ron.com>
Reviewed-by: Stanley Chu <stanley.chu@...iatek.com>
---
 drivers/scsi/ufs/ufshcd.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index bbc2607..e8f7f9d 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1518,6 +1518,11 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
 		 */
 		if (ufshcd_can_hibern8_during_gating(hba) &&
 		    ufshcd_is_link_hibern8(hba)) {
+			if (async) {
+				rc = -EAGAIN;
+				hba->clk_gating.active_reqs--;
+				break;
+			}
 			spin_unlock_irqrestore(hba->host->host_lock, flags);
 			flush_work(&hba->clk_gating.ungate_work);
 			spin_lock_irqsave(hba->host->host_lock, flags);
-- 
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