On Mon, Sep 23, 2024 at 06:05:53PM +0800, dengjie03 wrote: > Reproduction of the problem: During the S4 stress test, > when a USB device is inserted or removed, there is a > probability that the S4 wakeup will turn into a reboot. > The following two points describe how to analyze and > locate the problem points: > > 1. During the boot stage when S4 is awakened, after > the USB RootHub is initialized,it will enter the > runtime suspend state. From then on, whenever an > xhci port change event occurs, it will trigger a > remote wakeup request event and add wakeup_work to > pm_wq, where the subsequent RootHub runtime resume > process will be handled by pm_wq. > > xhci runtime suspend flow: > S4 boot > |->xhci init > |->register_root_hub > |->hub_probe > |->callback = RPM_GET_CALLBACK(dev, runtime_suspend) /* xhci RootHub runtime suspend */ > > xhci runtime resume flow : > xhci_irq() > |->xhci_handle_event() > |->handle_port_status() > |->if(hcd->state == HC_STATE_SUSPENDED) > |->usb_hcd_resume_root_hub() > |->set_bit(HCD_FLAG_WAKEUP_PENDING, &hcd->flags) /* wakeup pending signal to be set */ > |->queue_work(pm_wq, &hcd->wakeup_work) > |->hcd_resume_work() /* hcd->wakeup_work */ > |->usb_remote_wakeup() > |->callback = RPM_GET_CALLBACK(dev, runtime_resume) > |->usb_runtime_resume() /* usb runtime resume */ > |->generic_resume() > |->hcd_bus_resume() > |->clear_bit(HCD_FLAG_WAKEUP_PENDING, &hcd->flags); > /* wakeup pending signal to be clear */ > > 2. However, during the quiesce phase of S4 wakeup, > freeze_kernel_threads() will freeze this pm_wq, > and between freeze_kernel_threads() and dpm_suspend_start(), > there exists a very time-consuming S4 image loading process. > This leads to a situation where, if an xhci port change event occurs > after freeze_kernel_threads(), triggering the wakeup pending > signal to be set,but it cannot be processed by pm_wq to clear > this wakeup_pending bit, it will result in a subsequent > dpm_suspend_start() where USB suspend_common() detects the > wakeup pending signal being set and returns an -EBUSY error, > interrupting the S4 quiesce process and reverting to a reboot. > > S4 wakeup > |->resume_store > |->software_resume() > |->freeze_kernel_threads() /* will freeze pm_wq */ > |->load_image_and_restore() > |->swsusp_read() /* S4 image loading: time-consuming . > When an xhci port change event occurs at this point, it triggers the wakeup pending signal to be set. > However, since the pm_wq is in a frozen state, the wakeup_pending bit cannot be cleared.*/ > |->hibernation_restore > |->dpm_suspend_start(PMSG_QUIESCE) > |->hcd_pci_suspend() > |->suspend_common() > |->if (do_wakeup && HCD_WAKEUP_PENDING(hcd)) return -EBUSY; > > Below is a description of the countermeasures taken to address this issue: > 1. Considering the restore process that occurs after > the quiesce phase during S4 wakeup, which essentially > resets all root hubs,checking this wakeup pending status > in USB suspend_common() during the quiesce phase is of > little significance and should therefore be filtered out. > > S4 wakeup restore phase > |->dpm_resume(PMSG_RESTORE) > |->hcd_pci_restore() > |->xhci_resume() /* reset all root hubs */ > > Fixes: 3904bdf0821c40352495f632862637080e6bd744(PM: hibernate: Freeze kernel threads in software_resume()) Please read the documentation for how to list a Fixes: tag, it should be a bit smaller than this line :) > Signed-off-by: xiongxin <xiongxin@xxxxxxxxxx> > Co-developed-by: dengjie03 <dengjie03@xxxxxxxxxx> As the documentation states, we need real names, not email aliases. And fix up how you use co-developed-by please, again, the documentation shows how to do so. > --- > drivers/base/power/main.c | 5 +++++ > drivers/usb/core/hcd-pci.c | 21 ++++++++++++++------- > include/linux/pm.h | 1 + > 3 files changed, 20 insertions(+), 7 deletions(-) > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > index fb4d18a0b185..264d08b9e331 100644 > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -559,6 +559,11 @@ bool dev_pm_may_skip_resume(struct device *dev) > return !dev->power.must_resume && pm_transition.event != PM_EVENT_RESTORE; > } > > +bool is_pm_queisce(void) Bad name for a global function :( > +{ > + return pm_transition.event == PM_EVENT_QUIESCE; What happens if it changes right after this? Where is the locking involved? And why does USB only care about this and no other subsystem? thanks, greg k-h