Messages in this thread Patch in this message | | | Date | Wed, 22 Aug 2018 17:30:14 +0200 | From | Peter Zijlstra <> | Subject | [PATCH 2/4] mm/tlb: Remove tlb_remove_table() non-concurrent condition |
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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@kernel.org Cc: Nicholas Piggin <npiggin@gmail.com> Cc: David Miller <davem@davemloft.net> Cc: Will Deacon <will.deacon@arm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Fixes: 267239116987 ("mm, powerpc: move the RCU page-table freeing into generic code") Reported-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- mm/memory.c | 9 --------- 1 file changed, 9 deletions(-)
--- a/mm/memory.c +++ b/mm/memory.c @@ -375,15 +375,6 @@ void tlb_remove_table(struct mmu_gather { struct mmu_table_batch **batch = &tlb->batch; - /* - * When there's less then two users of this mm there cannot be a - * concurrent page-table walk. - */ - if (atomic_read(&tlb->mm->mm_users) < 2) { - __tlb_remove_table(table); - return; - } - if (*batch == NULL) { *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN); if (*batch == NULL) {
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