linux-kernel - [PATCH] scsi: ufs-qcom: Fix scheduling while atomic issue

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Date:   Mon, 25 May 2020 13:41:25 -0700
From:   Jeffrey Hugo <jeffrey.l.hugo@...il.com>
To:     agross@...nel.org, bjorn.andersson@...aro.org,
        alim.akhtar@...sung.com, avri.altman@....com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, subhashj@...eaurora.org,
        venkatg@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jeffrey Hugo <jeffrey.l.hugo@...il.com>
Subject: [PATCH] scsi: ufs-qcom: Fix scheduling while atomic issue

ufs_qcom_dump_dbg_regs() uses usleep_range, a sleeping function, but can
be called from atomic context in the following flow:

ufshcd_intr -> ufshcd_sl_intr -> ufshcd_check_errors ->
ufshcd_print_host_regs -> ufshcd_vops_dbg_register_dump ->
ufs_qcom_dump_dbg_regs

This causes a boot crash on the Lenovo Miix 630 when the interrupt is
handled on the idle thread.

Fix the issue by switching to udelay().

Fixes: 9c46b8676271 ("scsi: ufs-qcom: dump additional testbus registers")
Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>
---
 drivers/scsi/ufs/ufs-qcom.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
index 19aa5c44e0da..f938867301a0 100644
--- a/drivers/scsi/ufs/ufs-qcom.c
+++ b/drivers/scsi/ufs/ufs-qcom.c
@@ -1658,11 +1658,11 @@ static void ufs_qcom_dump_dbg_regs(struct ufs_hba *hba)
 
 	/* sleep a bit intermittently as we are dumping too much data */
 	ufs_qcom_print_hw_debug_reg_all(hba, NULL, ufs_qcom_dump_regs_wrapper);
-	usleep_range(1000, 1100);
+	udelay(1000);
 	ufs_qcom_testbus_read(hba);
-	usleep_range(1000, 1100);
+	udelay(1000);
 	ufs_qcom_print_unipro_testbus(hba);
-	usleep_range(1000, 1100);
+	udelay(1000);
 }
 
 /**
-- 
2.17.1