lkml.org 
[lkml]   [2022]   [Aug]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/9] slub: Make PREEMPT_RT support less convoluted
On 2022-08-18 16:37:06 [+0200], Vlastimil Babka wrote:
> > The slub fastpath does not interfere with slow path operations and the
>
> That's true on !PREEMPT_RT because a slowpath operation under
> local_lock_irqsave() will disable interrupts, so there can't be a
> fastpath operation in an interrupt handler appearing in the middle of a
> slowpath operation.
>
> On PREEMPT_RT local_lock_irqsave() doesn't actually disable interrupts,
> so that can happen. IIRC we learned that the hard way when Mike
> Galbraith was testing early versions of my PREEMPT_RT changes for SLUB.

I think the point is that local_lock_irqsave() does not disable
preemption. So the lock owner (within the local_lock_irqsave() section)
can be preempted and another task can use the fast path which does not
involve the lock and things go boom from here.

Sebastian

\
 
 \ /
  Last update: 2022-08-18 17:25    [W:0.420 / U:1.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site