From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx198.postini.com [74.125.245.198]) by kanga.kvack.org (Postfix) with SMTP id B90236B004D for ; Tue, 27 Dec 2011 18:43:53 -0500 (EST) Date: Tue, 27 Dec 2011 15:43:52 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page Message-Id: <20111227154352.0595b3a8.akpm@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Hillf Danton Cc: linux-mm@kvack.org, LKML , Michal Hocko , KAMEZAWA Hiroyuki On Fri, 23 Dec 2011 21:35:25 +0800 Hillf Danton wrote: > From: Hillf Danton > Subject: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page > > If huge page is enqueued under the protection of hugetlb_lock, then > the operation is atomic and safe. > > Cc: Michal Hocko > Cc: KAMEZAWA Hiroyuki > Cc: Andrew Morton > Signed-off-by: Hillf Danton > --- > > --- a/mm/hugetlb.c Tue Dec 20 21:26:30 2011 > +++ b/mm/hugetlb.c Fri Dec 23 21:16:28 2011 > @@ -901,7 +901,6 @@ retry: > h->resv_huge_pages += delta; > ret = 0; > > - spin_unlock(&hugetlb_lock); > /* Free the needed pages to the hugetlb pool */ > list_for_each_entry_safe(page, tmp, &surplus_list, lru) { > if ((--needed) < 0) > @@ -915,6 +914,7 @@ retry: > VM_BUG_ON(page_count(page)); > enqueue_huge_page(h, page); > } > + spin_unlock(&hugetlb_lock); > > /* Free unnecessary surplus pages to the buddy allocator */ btw, /* Free the needed pages to the hugetlb pool */ list_for_each_entry_safe(page, tmp, &surplus_list, lru) { if ((--needed) < 0) break; list_del(&page->lru); /* * This page is now managed by the hugetlb allocator and has * no users -- drop the buddy allocator's reference. */ put_page_testzero(page); VM_BUG_ON(page_count(page)); enqueue_huge_page(h, page); } spin_unlock(&hugetlb_lock); That VM_BUG_ON() largely duplicates the one in put_page_testzero(). (Putting a VM_BUG_ON() in put_page_testzero() was pretty expensive, too. I wonder how many people are enabling VM_BUG_ON()? We should be sparing in using these things) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org