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SubjectRe: [PATCH] mm: trace tlb flush after disabling preemption in try_to_unmap_flush
On Thu 16-07-15 15:35:39, Sasha Levin wrote:
> Commit "mm: send one IPI per CPU to TLB flush all entries after unmapping
> pages" added a trace_tlb_flush() while preemption was still enabled. This
> means that we'll access smp_processor_id() which in turn will get us quite
> a few warnings.
>
> Fix it by moving the trace to where the preemption is disabled, one line
> down.
>
> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

Reviewed-by: Michal Hocko <mhocko@suse.com>

> ---
>
> The diff is all lies: I've moved trace_tlb_flush() one line down rather
> than get_cpu() a line up ;)
>
> mm/rmap.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 30812e9..63ba46c 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -613,9 +613,10 @@ void try_to_unmap_flush(void)
> if (!tlb_ubc->flush_required)
> return;
>
> + cpu = get_cpu();
> +
> trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, -1UL);
>
> - cpu = get_cpu();
> if (cpumask_test_cpu(cpu, &tlb_ubc->cpumask))
> percpu_flush_tlb_batch_pages(&tlb_ubc->cpumask);
>
> --
> 1.7.10.4
>
> --
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--
Michal Hocko
SUSE Labs


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