Hi, > On Thu, Mar 12, 2015 at 04:33:41AM +0000, yoshihiro shimoda wrote: > > Hi Geert-san again, > > > > > Hi Geert-san, > > > > > > Thank you for the reply again! > > > > > > > Hi Shimoda-san, > > > > > > > > On Mon, Feb 16, 2015 at 2:52 AM, Yoshihiro Shimoda > > > > <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote: > > > > > According to the gadget.h, a "complete" function will always be called > > > > > with interrupts disabled. However, sometimes usbhsg_queue_pop() function > > > > > is called with interrupts enabled. So, this function should calls > > > > > local_irq_save() before this calls the usb_gadget_giveback_request(). > > > > > Otherwise, there is possible to cause a spinlock suspected in a gadget > > > > > complete function. > > > > > > > > I still feel uneasy about adding the call to local_irq_save(), as the need for > > > > this is usually an indicator of another locking problem. > > > > > > I also think that I would like to avoid using local_irq_save(). > > > But, I have no idea to resolve this issue for now. > > > > After I modified usb-dmac driver to use a tasklet instead of a kthread, > > this issue disappeared. > > > > My understanding is the followings: > > - According to the backtrace below, during usbhsf_dma_complete() was running, > > a softirq happened. After ncm_tx_tasklet() was called, the issue happened. > > http://thread.gmane.org/gmane.linux.usb.general/122023/focus=43729 > > > > - This means that usbhsf_dma_complete() ran on a kthread. So, ncm driver is able > > to do the ncm_tx_tasklet(). > > > > - After the current usb-dmac driver, since usbhsf_dma_complete() runs on a tasklet, > > ncm driver is not able to do the ncm_tx_tasklet during usbhsf_dma_complete() was running. > > > > > > So, I would like to recall this patch and I will resubmit this patch series as v3. > > try something like below: > > diff --git a/drivers/usb/renesas_usbhs/mod_gadget.c b/drivers/usb/renesas_usbhs/mod_gadget.c > index e0384af77e56..e9d75d85be59 100644 > --- a/drivers/usb/renesas_usbhs/mod_gadget.c > +++ b/drivers/usb/renesas_usbhs/mod_gadget.c > @@ -119,7 +119,7 @@ struct usbhsg_recip_handle { > /* > * queue push/pop > */ > -static void usbhsg_queue_pop(struct usbhsg_uep *uep, > +static void __usbhsg_queue_pop(struct usbhsg_uep *uep, > struct usbhsg_request *ureq, > int status) > { > @@ -133,6 +133,15 @@ static void usbhsg_queue_pop(struct usbhsg_uep *uep, > usb_gadget_giveback_request(&uep->ep, &ureq->req); > } > > +static void usbhsg_queue_pop(struct usbhsg_uep *uep, > + struct usbhsg_request *ureq, > + int status) > +{ > + usbhs_lock(priv, flags); > + __usbhsg_queue_pop(uep, ureq, status); > + usbhs_unlock(priv, flags); > +} > + > static void usbhsg_queue_done(struct usbhs_priv *priv, struct usbhs_pkt *pkt) > { > struct usbhs_pipe *pipe = pkt->pipe; > > > then, for cases where lock is already held you call __usbhsg_queue_pop() > and for all other cases, call usbhsg_queue_pop(). Thank you for the suggestion. However, we cannot use this usbhsg_queue_pop() because a gadget driver might call usb_ep_queue() in the "complete" function and this driver calls usbhs_lock() in the usb_ep_queue(). Perhaps my explanation was bad, but this issue was caused by the following conditions: - I use the renesas_usbhs driver as udc. - I use an old usb-dmac driver that the callback runs on a kthread. - I use the ncm driver. In this environment, the ncm driver might cause a spinlock suspected. As an old solution, I fixed the renesas_usbhs driver by this patch. However, if I use a new usb-dmac driver that the callback runs on a tasklet, I don't need this patch. (This is a new solution.) Best regards, Yoshihiro Shimoda -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
