lkml.org 
[lkml]   [2015]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: irq_fpu_usable() is false in ndo_start_xmit() for UDP packets
    From
    Hi David,

    On Mon, Nov 16, 2015 at 9:32 PM, David Miller <davem@davemloft.net> wrote:
    > Network device driver transmit executes with software interrupts
    > disabled.
    >
    > Therefore on x86, you cannot use the FPU.

    That is extremely problematic for me. Is there a way to make this not
    so? A driver flag that would allow this?

    Also - how come it irq_fpu_usable() is true when using TCP but not
    when using UDP?

    Further, irq_fpu_usable() doesn't only check for interrupts. There are
    two other conditions that allow the FPU's usage, from
    arch/x86/kernel/fpu/core.c:

    bool irq_fpu_usable(void)
    {
    return !in_interrupt() ||
    interrupted_user_mode() ||
    interrupted_kernel_fpu_idle();
    }


    \
     
     \ /
      Last update: 2015-11-16 22:21    [W:3.510 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site