lkml.org 
[lkml]   [2017]   [Dec]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: x86/pti: smp_processor_id() called while preemptible in resume-from-sleep
From
Date


--Andy

> On Dec 30, 2017, at 11:15 AM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> On Sat, Dec 30, 2017 at 11:03 AM, Dave Hansen
> <dave.hansen@linux.intel.com> wrote:
>> On 12/30/2017 10:40 AM, Linus Torvalds wrote:
>>> The __native_flush_tlb() function looks _very_ broken.
>> ...
>>> So I'd suggest moving the preempt_disable() up to the top of that
>>> function, regardless of whether we could then remove that seemingly
>>> stale TLB flush in that crazy
>>> smpboot_setup/restore_warm_reset_vector() dance...
>>
>> If someone is calling __native_flush_tlb(), shouldn't they already be in
>> a state where they can't be preempted? It's fundamentally a one-cpu
>> thing, both the actual CPU TLB flush _and_ the per-cpu variables.
>
> Hmm. I think you're right.
>
>> It seems like we might want to _remove_ the explicit
>> preempt_dis/enable() from here:
>>
>> preempt_disable();
>> native_write_cr3(__native_read_cr3());
>> preempt_enable();
>>
>> and add some warnings to ensure it's disabled when we enter
>> __native_flush_tlb().
>
> Agreed, that would certainly also be consistent.
>
> The current code that disables preemption only selectively seems
> insane to me. Either all or nothing, not this crazy half-way thing.

Agreed. The current code is bogus. I'd rather have a warning if preemptible.

I'm reasonably confident that IRQs on but preempt off is okay.

>
> Linus

\
 
 \ /
  Last update: 2017-12-30 20:32    [W:0.067 / U:2.392 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site