On Tue, 2016-01-05 at 02:25 +0000, fx IWATA NOBUO wrote:
> Dear Oliver,
Hi Nobuosan,
>
> > You cannot honor GFP_NOIO
>
> GFP_NOIO is used in original kernel space transmission relating sk_buf.
> It is not used for userspace transmission.
But it is used in the class drivers, which use the HCD.
:~/gregKHusb/drivers/usb/storage> grep GFP_NOIO * | wc
51 277 2919
> I added 'if' statement around the block to skip the block where GFP_NOIO
> is used for kernel space transmission.
I don't really understand. How will this help? GFP_NOIO
is used only when it is needed or the IO could can deadlock
on itself.
Consider this:
1. URB for IO request to storage
2. Handed to user space
3. User space needs memory and causes kernel into laundering
4. kernel waits for IO on storage device
Regards
Oliver
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