Messages in this thread | | | Date | Tue, 19 Jun 2018 08:23:40 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86: Call fixup_exception() before notify_die() in math_error() |
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On Mon, 18 Jun 2018, Andy Lutomirski wrote:
> On Thu, Jun 14, 2018 at 10:10 PM Siarhei Liakh > <Siarhei.Liakh@concurrent-rt.com> wrote: > > > > fpu__drop() has an explicit fwait which under some conditions can trigger > > a fixable FPU exception while in kernel. Thus, we should attempt to fixup > > the exception first, and only call notify_die() if the fixup failed just > > like in do_general_protection(). The original call sequence incorrectly > > triggers KDB entry on debug kernels under particular FPU-intensive > > workloads. This issue had been privately observed, fixed, and tested > > on 4.9.98, while this patch brings the fix to the upstream. > > Reviewed-by: Andy Lutomirski <luto@kernel.org> > > With the caveat that you are perpetuating what is arguably a bug in > some of the other entries: math_error() can now be called with IRQs > off and return with IRQs on. If we actually start asserting good > behavior in the entry code, we'll need to fix this.
Confused. math_error() is still invoked with interrupts off. What's different now is that notify_die() is called with interrupts conditionally enabled while upstream it's always called with interrupts disabled.
Thanks,
tglx
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