Messages in this thread | | | Date | Tue, 19 Feb 2019 12:47:38 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v6 06/18] asm-generic/tlb: Conditionally provide tlb_migrate_finish() |
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On Tue, Feb 19, 2019 at 11:31:54AM +0100, Peter Zijlstra wrote: > Needed for ia64 -- alternatively we drop the entire hook. > > Cc: Will Deacon <will.deacon@arm.com> > Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Nick Piggin <npiggin@gmail.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > include/asm-generic/tlb.h | 2 ++ > 1 file changed, 2 insertions(+) > > --- a/include/asm-generic/tlb.h > +++ b/include/asm-generic/tlb.h > @@ -539,6 +539,8 @@ static inline void tlb_end_vma(struct mm > > #endif /* CONFIG_MMU */ > > +#ifndef tlb_migrate_finish > #define tlb_migrate_finish(mm) do {} while (0) > +#endif
Fine for now, but I agree that we should drop the hook altogether. AFAICT, this only exists to help an ia64 optimisation which looks suspicious to me since it uses:
mm == current->active_mm && atomic_read(&mm->mm_users) == 1
to identify a "single-threaded fork()" and therefore perform only local TLB invalidation. Even if this was the right thing to do, it's not clear to me that tlb_migrate_finish() is called on the right CPU anyway.
So I'd be keen to remove this hook before it spreads, but in the meantime:
Acked-by: Will Deacon <will.deacon@arm.com>
Will
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