Hi Peter,
On Wed, May 29, 2013 at 9:51 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> What about something like this?
With that patch I still get mtest05 firing my TLB/PTE incoherency check
in the UP PREEMPT_VOLUNTARY configuration. This happens after
zap_pte_range completion in the end of unmap_region because of
rescheduling called in the following call chain:
unmap_region
free_pgtables
unlink_anon_vmas
lock_anon_vma_root
down_write
might_sleep
might_resched
_cond_resched
>
> ---
> include/asm-generic/tlb.h | 11 ++++++++++-
> mm/memory.c | 17 ++++++++++++++++-
> 2 files changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
> index b1b1fa6..651b1cf 100644
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -116,6 +116,7 @@ struct mmu_gather {
>
> static inline int tlb_fast_mode(struct mmu_gather *tlb)
> {
> +#ifndef CONFIG_PREEMPT
> #ifdef CONFIG_SMP
> return tlb->fast_mode;
> #else
> @@ -124,7 +125,15 @@ static inline int tlb_fast_mode(struct mmu_gather *tlb)
> * and page free order so much..
> */
> return 1;
> -#endif
> +#endif /* CONFIG_SMP */
> +#else /* CONFIG_PREEMPT */
> + /*
> + * Since mmu_gather is preemptible, preemptible kernels are like SMP
> + * kernels, we must batch to make sure we invalidate TLBs before we
> + * free the pages.
> + */
> + return 0;
> +#endif /* CONFIG_PREEMPT */
> }
>
> void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
> diff --git a/mm/memory.c b/mm/memory.c
> index 6dc1882..e915af2 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -384,6 +384,21 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table)
>
> #endif /* CONFIG_HAVE_RCU_TABLE_FREE */
>
> +static inline void cond_resched_tlb(struct mmu_gather *tlb)
> +{
> +#ifndef CONFIG_PREEMPT
> + /*
> + * For full preempt kernels we must do regular batching like
> + * SMP, see tlb_fast_mode(). For !PREEMPT we can 'cheat' and
> + * do a flush before our voluntary 'yield'.
> + */
> + if (need_resched()) {
> + tlb_flush_mmu(tlb);
> + cond_resched();
> + }
> +#endif
> +}
> +
> /*
> * If a p?d_bad entry is found while walking page tables, report
> * the error, before resetting entry to p?d_none. Usually (but
> @@ -1264,7 +1279,7 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
> goto next;
> next = zap_pte_range(tlb, vma, pmd, addr, next, details);
> next:
> - cond_resched();
> + cond_resched_tlb(tlb);
> } while (pmd++, addr = next, addr != end);
>
> return addr;
>
>
--
Thanks.
-- Max
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