linux-kernel - [PATCH v2] usb: core: hub: fix race condition about TRSMRCY of resume

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Date:   Wed, 12 May 2021 10:07:38 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>
CC:     Matthias Brugger <matthias.bgg@...il.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Bixuan Cui <cuibixuan@...wei.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Oliver Neukum <oneukum@...e.com>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        Tianping Fang <tianping.fang@...iatek.com>,
        Eddie Hung <eddie.hung@...iatek.com>,
        Ikjoon Jang <ikjn@...omium.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        <stable@...r.kernel.org>
Subject: [PATCH v2] usb: core: hub: fix race condition about TRSMRCY of resume

This may happen if the port becomes resume status exactly
when usb_port_resume() gets port status, it still need provide
a TRSMCRY time before access the device.

CC: <stable@...r.kernel.org>
Acked-by: Alan Stern <stern@...land.harvard.edu>
Reported-by: Tianping Fang <tianping.fang@...iatek.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
---
v2:
    cc stable suggested by Alan,
    and add acked-by Alan
---
 drivers/usb/core/hub.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index b2bc4b7c4289..fc7d6cdacf16 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3642,9 +3642,6 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
 		 * sequence.
 		 */
 		status = hub_port_status(hub, port1, &portstatus, &portchange);
-
-		/* TRSMRCY = 10 msec */
-		msleep(10);
 	}
 
  SuspendCleared:
@@ -3659,6 +3656,9 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
 				usb_clear_port_feature(hub->hdev, port1,
 						USB_PORT_FEAT_C_SUSPEND);
 		}
+
+		/* TRSMRCY = 10 msec */
+		msleep(10);
 	}
 
 	if (udev->persist_enabled)
-- 
2.18.0