diff options
Diffstat (limited to 'include/linux/mm_types.h')
| -rw-r--r-- | include/linux/mm_types.h | 29 |
1 files changed, 26 insertions, 3 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 3cadee0a3508..dc1edec05a3f 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -535,6 +535,10 @@ extern void tlb_finish_mmu(struct mmu_gather *tlb, */ static inline bool mm_tlb_flush_pending(struct mm_struct *mm) { + /* + * Must be called with PTL held; such that our PTL acquire will have + * observed the store from set_tlb_flush_pending(). + */ return atomic_read(&mm->tlb_flush_pending) > 0; } @@ -556,10 +560,29 @@ static inline void inc_tlb_flush_pending(struct mm_struct *mm) atomic_inc(&mm->tlb_flush_pending); /* - * Guarantee that the tlb_flush_pending increase does not leak into the - * critical section updating the page tables + * The only time this value is relevant is when there are indeed pages + * to flush. And we'll only flush pages after changing them, which + * requires the PTL. + * + * So the ordering here is: + * + * atomic_inc(&mm->tlb_flush_pending); + * spin_lock(&ptl); + * ... + * set_pte_at(); + * spin_unlock(&ptl); + * + * spin_lock(&ptl) + * mm_tlb_flush_pending(); + * .... + * spin_unlock(&ptl); + * + * flush_tlb_range(); + * atomic_dec(&mm->tlb_flush_pending); + * + * So the =true store is constrained by the PTL unlock, and the =false + * store is constrained by the TLB invalidate. */ - smp_mb__before_spinlock(); } /* Clearing is done after a TLB flush, which also provides a barrier. */ |