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Date: Fri, 13 Jan 2012 10:14:25 -0500 From: Naoya Horiguchi <n-horiguchi@...jp.nec.com> To: Hillf Danton <dhillf@...il.com> CC: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, David Rientjes <rientjes@...gle.com>, Andi Kleen <andi@...stfloor.org>, Wu Fengguang <fengguang.wu@...el.com>, Andrea Arcangeli <aarcange@...hat.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 2/6] thp: optimize away unnecessary page table locking Hi Hillf, (1/13/2012 7:04), Hillf Danton wrote: [...] >> +/* >> + * Returns 1 if a given pmd is mapping a thp and stable (not under splitting.) >> + * Returns 0 otherwise. Note that if it returns 1, this routine returns without >> + * unlocking page table locks. So callers must unlock them. >> + */ >> +int pmd_trans_huge_stable(pmd_t *pmd, struct vm_area_struct *vma) >> +{ >> + VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem)); >> + >> + if (!pmd_trans_huge(*pmd)) >> + return 0; >> + >> + spin_lock(&vma->vm_mm->page_table_lock); >> + if (likely(pmd_trans_huge(*pmd))) { >> + if (pmd_trans_splitting(*pmd)) { >> + spin_unlock(&vma->vm_mm->page_table_lock); >> + wait_split_huge_page(vma->anon_vma, pmd); >> + return 0; >> + } else { > > spin_unlock(&vma->vm_mm->page_table_lock); yes? No. Unlocking is supposed to be done by the caller as commented. Thanks, Naoya > >> + /* Thp mapped by 'pmd' is stable, so we can >> + * handle it as it is. */ >> + return 1; >> + } >> + } >> + spin_unlock(&vma->vm_mm->page_table_lock); >> + return 0; >> +} >> + -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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