Messages in this thread |  | | From | Linus Torvalds <> | Date | Sat, 30 Dec 2017 12:45:39 -0800 | Subject | Re: x86/pti: smp_processor_id() called while preemptible in resume-from-sleep |
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On Sat, Dec 30, 2017 at 12:28 PM, Thomas Gleixner <tglx@linutronix.de> wrote: > > That preempt_disable()/enable() was added with: > > commit 5cf0791da5c162ebc14b01eb01631cfa7ed4fa6e > Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > Date: Fri Aug 5 15:37:39 2016 +0200 > > x86/mm: Disable preemption during CR3 read+write > > So we need to look at that scenario before removing it.
Good point, but I think that was actually a mis-feature of the old "__flush_tlb_up()" implementation that Andy got rid of in commit ce4a4e565f52 ("x86/mm: Remove the UP asm/tlbflush.h code, always use the (formerly) SMP code").
So the code sequence that that commit talks about no longer exists.
Instead, we now have the call to __flush_tlb() inside a get_cpu/put_cpu, which is preempt-safe even on UP (despite the CPU number obviously being fixed).
So I think Dave is right: we should just remove the preempt_disable/endable. But adding a
WARN_ON_ONCE(preemptible());
might still be a good idea.
Linus
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