Re: [PATCH 2/4] mm/tlb: Remove tlb_remove_table() non-concurrent condition

[Will Deacon]

On Wed, Aug 22, 2018 at 05:30:14PM +0200, Peter Zijlstra wrote:
> Will noted that only checking mm_users is incorrect; we should also
> check mm_count in order to cover CPUs that have a lazy reference to
> this mm (and could do speculative TLB operations).
> 
> If removing this turns out to be a performance issue, we can
> re-instate a more complete check, but in tlb_table_flush() eliding the
> call_rcu_sched().
> 
> Cc: stable@xxxxxxxxxx
> Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
> Cc: David Miller <davem@xxxxxxxxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Fixes: 267239116987 ("mm, powerpc: move the RCU page-table freeing into generic code")
> Reported-by: Will Deacon <will.deacon@xxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
>  mm/memory.c |    9 ---------
>  1 file changed, 9 deletions(-)

Acked-by: Will Deacon <will.deacon@xxxxxxx>

Cheers,

Will