Messages in this thread Patch in this message | | | Date | Tue, 16 Oct 2007 11:23:58 -0400 (EDT) | From | Alan Stern <> | Subject | Re: [Linux-usb-users] OHCI root_port_reset() deadly loop... |
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On Mon, 15 Oct 2007, David Miller wrote:
> I want to help with this, but if I even breath on the kernel the bug > goes away. The race just gets harder to trigger, and if we just keep > adding things it'll make the problem go away but for the absolutely > wrong reasons. > > The only way we will provably fix this is to make sure EHCI initialize > fully, first, regardless of kernel config or what userland does.
Unfortunately that simply isn't possible. No matter what you do, the user can always unload ehci-hcd and then load it back in again.
Do you have any idea _where_ in ohci_hub_control the hang still occurs? Is it the same unbounded reset loop?
Does the patch below satisfy both Davids?
Alan Stern
Index: usb-2.6/drivers/usb/host/ohci-hub.c =================================================================== --- usb-2.6.orig/drivers/usb/host/ohci-hub.c +++ usb-2.6/drivers/usb/host/ohci-hub.c @@ -560,10 +560,10 @@ static void start_hnp(struct ohci_hcd *o /* called from some task, normally khubd */ static inline int root_port_reset (struct ohci_hcd *ohci, unsigned port) { - __hc32 __iomem *portstat = &ohci->regs->roothub.portstatus [port]; - u32 temp; - u16 now = ohci_readl(ohci, &ohci->regs->fmnumber); - u16 reset_done = now + PORT_RESET_MSEC; + __hc32 __iomem *portstat = &ohci->regs->roothub.portstatus[port]; + u32 temp; + unsigned long reset_done = jiffies + + msecs_to_jiffies(PORT_RESET_MSEC); /* build a "continuous enough" reset signal, with up to * 3msec gap between pulses. scheduler HZ==100 must work; @@ -578,6 +578,8 @@ static inline int root_port_reset (struc return -ESHUTDOWN; if (!(temp & RH_PS_PRS)) break; + if (time_after(jiffies, reset_done)) + break; udelay (500); } @@ -589,8 +591,7 @@ static inline int root_port_reset (struc /* start the next reset, sleep till it's probably done */ ohci_writel (ohci, RH_PS_PRS, portstat); msleep(PORT_RESET_HW_MSEC); - now = ohci_readl(ohci, &ohci->regs->fmnumber); - } while (tick_before(now, reset_done)); + } while (time_before_eq(jiffies, reset_done)); /* caller synchronizes using PRSC */ return 0; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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