[linux-yocto] [PATCH] x86: lazy-preempt: use proper return label on 32bit-x86

[Bruce Ashfield]

On Mon, Mar 18, 2019 at 8:06 AM He Zhe <zhe.he at windriver.com> wrote:
>
> This is for
> v4.19/standard/preempt-rt/base
> v4.19/standard/preempt-rt/intel
> v4.19/standard/preempt-rt/intel-x86

Is this also part of an -rt stable/dev update ? It should be, but I
didn't have time to look today.

The reason I ask, is that I should do a refresh of -rt on 4.19, and if
this is part of the latest -rt updates, I'd rather pick them all up
versus cherry picking just a single change.

Bruce

>
> Zhe
>
> On 3/18/19 8:04 PM, zhe.he at windriver.com wrote:
> > From: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
> >
> > The lazy-preempt uses the wrong return label in case preemption isn't
> > possible. This results crash while returning to the kernel.
> >
> > Use the correct return label if preemption isn' possible.
> >
> > Reported-by: Andri Yngvason <andri at yngvason.is>
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
> >
> > commit 2c85fda444207949be4ad5e38a49ee8b4e5171cb upstream
> >
> > Fix x86 32bit boot failure and hang.
> >
> > Signed-off-by: He Zhe <zhe.he at windriver.com>
> > ---
> >  arch/x86/entry/entry_32.S | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
> > index 0169c25..e6f61c8 100644
> > --- a/arch/x86/entry/entry_32.S
> > +++ b/arch/x86/entry/entry_32.S
> > @@ -773,15 +773,15 @@ ENTRY(resume_kernel)
> >
> >       # atleast preempt count == 0 ?
> >       cmpl $_PREEMPT_ENABLED,PER_CPU_VAR(__preempt_count)
> > -     jne restore_all
> > +     jne     restore_all_kernel
> >
> >       movl    PER_CPU_VAR(current_task), %ebp
> >       cmpl    $0,TASK_TI_preempt_lazy_count(%ebp)     # non-zero preempt_lazy_count ?
> > -     jnz     restore_all
> > +     jnz     restore_all_kernel
> >
> >       testl   $_TIF_NEED_RESCHED_LAZY, TASK_TI_flags(%ebp)
> > -     jz      restore_all
> > -     test_int_off:
> > +     jz      restore_all_kernel
> > +test_int_off:
> >  #endif
> >       testl   $X86_EFLAGS_IF, PT_EFLAGS(%esp) # interrupts off (exception path) ?
> >       jz      restore_all_kernel
>


-- 
- Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end
- "Use the force Harry" - Gandalf, Star Trek II