lkml.org 
[lkml]   [2015]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 3/4] x86/fpu: use restore_init_xstate() instead of math_state_restore() on kthread exec
    On Wed, Mar 11, 2015 at 06:34:49PM +0100, Oleg Nesterov wrote:
    > Change flush_thread() to do user_fpu_begin() + restore_init_xstate()
    > and avoid math_state_restore().
    >
    > Note: "TODO: cleanup this horror" is still valid. We do not need
    > init_fpu() at all, we only need fpu_alloc() + memset(0). But this needs
    > other changes, in particular user_fpu_begin() should set used_math().
    >
    > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    > ---
    > arch/x86/kernel/process.c | 3 ++-
    > 1 files changed, 2 insertions(+), 1 deletions(-)
    >
    > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
    > index dd9a069..c396de2 100644
    > --- a/arch/x86/kernel/process.c
    > +++ b/arch/x86/kernel/process.c
    > @@ -142,7 +142,8 @@ void flush_thread(void)
    > /* kthread execs. TODO: cleanup this horror. */
    > if (WARN_ON(init_fpu(current)))
    > force_sig(SIGKILL, current);
    > - math_state_restore();
    > + user_fpu_begin();
    > + restore_init_xstate();

    Ok, question: so math_state_restore() does kernel_fpu_disable() before
    doing those, why is it ok for flush_thread() to not do it?

    --
    Regards/Gruss,
    Boris.

    ECO tip #101: Trim your mails when you reply.
    --


    \
     
     \ /
      Last update: 2015-03-13 12:01    [W:2.515 / U:0.420 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site