Messages in this thread | | | From | Linus Torvalds <> | Date | Sat, 30 Dec 2017 11:15:02 -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 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.
Linus
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