Messages in this thread | | | Date | Mon, 21 Jun 2021 09:37:34 +0800 | From | linyyuan@codeauro ... | Subject | Re: [PATCH v3 1/2] usb: udc: core: hide struct usb_gadget_driver to gadget driver |
| |
On 2021-06-20 21:47, Alan Stern wrote: > On Sun, Jun 20, 2021 at 11:53:18AM +0800, linyyuan@codeaurora.org > wrote: >> On 2021-06-20 11:46, linyyuan@codeaurora.org wrote: >> > On 2021-06-20 10:13, Alan Stern wrote: >> > > On Sat, Jun 19, 2021 at 11:43:08PM +0800, Linyu Yuan wrote: >> > > > currently most gadget driver have a pointer to save >> > > > struct usb_gadget_driver from upper layer, >> > > > it allow upper layer set and unset of the pointer. >> > > > >> > > > there is race that upper layer unset the pointer first, >> > > > but gadget driver use the pointer later, >> > > > and it cause system crash due to NULL pointer access. >> > > >> > > This race has already been fixed in Greg's usb-next branch. See >> > > commit >> > > 7dc0c55e9f30 ("USB: UDC core: Add udc_async_callbacks gadget op") and >> > > following commits 04145a03db9d ("USB: UDC: Implement >> > > udc_async_callbacks in dummy-hcd") and b42e8090ba93 ("USB: UDC: >> > > Implement udc_async_callbacks in net2280"). >> > > >> > thanks, this is better, lower driver only need change several places. >> > > You just need to write a corresponding patch implementing the >> > > async_callbacks op for dwc3. >> > yes, i will do. >> > > >> Alan, i want to discuss your suggestion again in b42e8090ba93 ("USB: >> UDC: >> Implement udc_async_callbacks in net2280") >> >> + if (dev->async_callbacks) { ----> if CPU1 saw >> this >> is true >> + spin_unlock(&dev->lock); ---> CPU2 get >> lock >> after this unlock, >> it will set async_callbacks to false, then follow call also crash, >> right ? >> + tmp = dev->driver->setup(&dev->gadget, >> &u.r); >> + spin_lock(&dev->lock); >> + } > > No, this is okay. The reason is because usb_gadget_remove_driver (CPU2 > in your example) does this: > > usb_gadget_disable_async_callbacks(udc); > if (udc->gadget->irq) > synchronize_irq(udc->gadget->irq); > udc->driver->unbind(udc->gadget); > usb_gadget_udc_stop(udc); > > The synchronize_irq call will make CPU2 wait until CPU1 has finished > handling the interrupt for the setup packet. The system won't crash, > because dev->driver->setup will be called before unbind and udc_stop > instead of after. still several question, 1. how about suspend calll dev->driver->suspend ? 2. will 04145a03db9d ("USB: UDC: Implement udc_async_callbacks in dummy-hcd") backport to LTS branch ? 3. how about coding style ? so following code if (foo->gadget_driver && foo->gadget_driver->resume) change to if (foo->asnyc_callbacks && foo->gadget_driver->resume) > > Alan Stern
| |