Re: [PATCH v7 3/5] usb: host: ohci-sm501: init genalloc for local memory

Guenter Roeck
2019-06-13T18:05:47Z

On 6/13/19 8:34 AM, Fredrik Noring wrote:
> Hi Guenter,
>
>> Thanks for the confirmation. Do you see the problem only with the
>> ohci-sm501 driver or also with others ?
>
> All are likely affected, but it depends, because I believe the problem is
> that the USB subsystem runs out of memory. Please try the attached patch!
>
> The pool assumed 4096 byte page alignment for every allocation, which is
> excessive given that many requests are for 16 and 32 bytes. In the patch
> below, I have turned down the order to 5, which is good enough for the ED
> and TD structures of the OHCI, but not enough for the HCCA that needs 256
> byte alignment. With some luck, the WARN_ON_ONCE will not trigger in your
> test, though. If it does, you may try to increase the order from 5 to 8.
>

You are right, the patch below fixes the problem. I did not get the warning
with order==5. Nevertheless, I also tested with order==8; that works as well.

Thanks a lot for tracking this down!
Guenter

> I have observed strange things happen when the USB subsystem runs out of
> memory. The mass storage drivers often seem to busy-wait on -ENOMEM,
> consuming a lot of processor resources. It would be much more efficient
> to sleep waiting for memory to become available.
>
> In your case I suspect that allocation failures are not correctly
> attributed. Certain kinds of temporary freezes may also occur, as the
> various devices are reset due to host memory allocation errors.
> > Fredrik
>
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -3011,7 +3011,7 @@ int usb_hcd_setup_local_mem(struct usb_hcd *hcd, phys_addr_t phys_addr,
> int err;
> void __iomem *local_mem;
>
> - hcd->localmem_pool = devm_gen_pool_create(hcd->self.sysdev, PAGE_SHIFT,
> + hcd->localmem_pool = devm_gen_pool_create(hcd->self.sysdev, 5,
> dev_to_node(hcd->self.sysdev),
> dev_name(hcd->self.sysdev));
> if (IS_ERR(hcd->localmem_pool))
> diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
> --- a/drivers/usb/host/ohci-hcd.c
> +++ b/drivers/usb/host/ohci-hcd.c
> @@ -517,6 +517,7 @@ static int ohci_init (struct ohci_hcd *ohci)
> GFP_KERNEL);
> if (!ohci->hcca)
> return -ENOMEM;
> + WARN_ON_ONCE(ohci->hcca_dma & 0xff);
>
> if ((ret = ohci_mem_init (ohci)) < 0)
> ohci_stop (hcd);
>