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[(223.70.160.255)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 883973010; Tue, 10 Sep 2024 18:57:29 +0800 From: Duan Chenghao To: stern@rowland.harvard.edu Cc: gregkh@linuxfoundation.org, pavel@ucw.cz, linux-pm@vger.kernel.org, niko.mauno@vaisala.com, stanley_chang@realtek.com, duanchenghao@kylinos.cn Subject: [PATCH v2] USB: Fix the issue of task recovery failure caused by USB status when S4 wakes up Date: Tue, 10 Sep 2024 18:57:14 +0800 Message-Id: <20240910105714.148976-1-duanchenghao@kylinos.cn> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 When a device is inserted into the USB port and an S4 wakeup is initiated, after the USB-hub initialization is completed, it will automatically enter suspend mode. Upon detecting a device on the USB port, it will proceed with resume and set the hcd to the HCD_FLAG_WAKEUP_PENDING state. During the S4 wakeup process, peripherals are put into suspend mode, followed by task recovery. However, upon detecting that the hcd is in the HCD_FLAG_WAKEUP_PENDING state, it will return an EBUSY status, causing the S4 suspend to fail and subsequent task recovery to not proceed. S4 waking up from hibernation ============================= kernel initialization | v freeze user task and kernel thread | v load saved image | v freeze the peripheral device and controller(*** Error point ***) (Check the HCD_FLAG_WAKEUP_ PENDING flag of the USB. If it is set, return to EBUSY and do not perform the following restore image.) | v restore image(task recovery) This patch makes two modifications in total: 1. The set_bit and clear_bit operations for the HCD_FLAG_WAKEUP_PENDING flag of Hcd, which were previously split between the top half and bottom half of the interrupt,are now unified and executed solely in the bottom half of the interrupt.This prevents the bottom half tasks from being frozen during the S4 process,ensuring that the clear_bit process can proceed without interruption. Before modification： ehci interrupt handler ===================== remote wakeup if (ehci->rh_state == EHCI_RH_SUSPENDED) | usb_hcd_resume_root_hub | | | v | top half set_bit HCD_FLAG_WAKEUP_PENDING | | | v | queue_work(pm_wq, &hcd->wakeup_work) | | v hub resume | | | v | bottom half clear_bit HCD_FLAG_WAKEUP_PENDING | After modification: ehci interrupt handler ===================== remote wakeup if (ehci->rh_state == EHCI_RH_SUSPENDED) | usb_hcd_resume_root_hub | | | top half v | queue_work(pm_wq, &hcd->wakeup_work) | | v set_bit HCD_FLAG_WAKEUP_PENDING | | | v | hub resume | bottom half | | v | clear_bit HCD_FLAG_WAKEUP_PENDING | 2. Add a condition to the set_bit operation for the hcd flags HCD_FLAG_WAKEUP_PENDING.When the hcd status is HC_STATE_SUSPENDED, perform the setting of the aforementioned status bit.This prevents a subsequent set_bit from occurring after the clear_bit if the hcd is in the resuming process. Before modification： ehci interrupt handler(CPUx) ehci init(CPUy) ===================== ============= remote wakeup initialization complete usb_hcd_resume_root_hub Enter suspend and detect that there is a device inserted (udev->state = USB_STATE_SUSPENDED) hcd->state = HC_STATE_RESUMING bus_resume if (udev->state == USB_STATE_SUSPENDED) clear_bit HCD_FLAG_WAKEUP_PENDING set_bit HCD_FLAG_WAKEUP_PENDING udev->state = !USB_STATE_SUSPENDED In the aforementioned scenario, there is no mutual exclusion between the set_bit operation in ehci interrupts, the judgment of udev->state, and the clear_bit as well as the assignment of udev->state during ehci initialization. There exists a situation where clear_bit is followed by set_bit, but due to the judgment on udev->state, the clear_bit operation might not occur again, leading to an error in the flag bit. After modification: ehci interrupt handler(CPUx) ehci init(CPUy) ===================== ============= remote wakeup initialization complete usb_hcd_resume_root_hub Enter suspend and detect that there is a device inserted (udev->state = USB_STATE_SUSPENDED) hcd->state = HC_STATE_RESUMING bus_resume if (udev->state == USB_STATE_SUSPENDED) clear_bit HCD_FLAG_WAKEUP_PENDING if (hcd->state != HC_STATE_RESUMING) udev->state = !USB_STATE_SUSPENDED set_bit HCD_FLAG_WAKEUP_PENDING Signed-off-by: Duan Chenghao --- drivers/usb/core/hcd.c | 1 - drivers/usb/core/hub.c | 3 +++ 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index 1ff7d901fede..a6bd0fbd82f4 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -2389,7 +2389,6 @@ void usb_hcd_resume_root_hub (struct usb_hcd *hcd) spin_lock_irqsave (&hcd_root_hub_lock, flags); if (hcd->rh_registered) { pm_wakeup_event(&hcd->self.root_hub->dev, 0); - set_bit(HCD_FLAG_WAKEUP_PENDING, &hcd->flags); queue_work(pm_wq, &hcd->wakeup_work); } spin_unlock_irqrestore (&hcd_root_hub_lock, flags); diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 4b93c0bd1d4b..7f847c4afc0d 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -3835,11 +3835,14 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg) int usb_remote_wakeup(struct usb_device *udev) { + struct usb_hcd *hcd = bus_to_hcd(udev->bus); int status = 0; usb_lock_device(udev); if (udev->state == USB_STATE_SUSPENDED) { dev_dbg(&udev->dev, "usb %sresume\n", "wakeup-"); + if (hcd->state == HC_STATE_SUSPENDED) + set_bit(HCD_FLAG_WAKEUP_PENDING, &hcd->flags); status = usb_autoresume_device(udev); if (status == 0) { /* Let the drivers do their thing, then... */