From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f176.google.com (mail-wi0-f176.google.com [209.85.212.176]) by kanga.kvack.org (Postfix) with ESMTP id 2F81B6B0032 for ; Sun, 8 Mar 2015 17:23:58 -0400 (EDT) Received: by widem10 with SMTP id em10so862059wid.2 for ; Sun, 08 Mar 2015 14:23:57 -0700 (PDT) Received: from mail-wg0-x236.google.com (mail-wg0-x236.google.com. [2a00:1450:400c:c00::236]) by mx.google.com with ESMTPS id dt1si13458191wib.120.2015.03.08.14.23.56 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 08 Mar 2015 14:23:56 -0700 (PDT) Received: by wggy19 with SMTP id y19so6993461wgg.9 for ; Sun, 08 Mar 2015 14:23:56 -0700 (PDT) Date: Sun, 8 Mar 2015 17:23:53 -0400 From: Michal Hocko Subject: Re: mm: hangs in free_pages_prepare Message-ID: <20150308212353.GB10442@dhcp22.suse.cz> References: <54FB4590.20102@oracle.com> <20150308203838.GA10442@dhcp22.suse.cz> <54FCB5D6.1090803@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54FCB5D6.1090803@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin Cc: "linux-mm@kvack.org" , "akpm >> Andrew Morton" On Sun 08-03-15 16:49:26, Sasha Levin wrote: > On 03/08/2015 04:38 PM, Michal Hocko wrote: > > On Sat 07-03-15 13:38:08, Sasha Levin wrote: > > [...] > >> [ 1573.730097] ? kasan_free_pages (mm/kasan/kasan.c:301) > >> [ 1573.788680] free_pages_prepare (mm/page_alloc.c:791) > >> [ 1573.788680] ? free_hot_cold_page (./arch/x86/include/asm/paravirt.h:809 (discriminator 2) mm/page_alloc.c:1579 (discriminator 2)) > >> [ 1573.788680] free_hot_cold_page (mm/page_alloc.c:1543) > >> [ 1573.788680] __free_pages (mm/page_alloc.c:2957) > >> [ 1573.788680] ? __vunmap (mm/vmalloc.c:1460 (discriminator 2)) > >> [ 1573.788680] __vunmap (mm/vmalloc.c:1460 (discriminator 2)) > > > > __vunmap is doing: > > for (i = 0; i < area->nr_pages; i++) { > > struct page *page = area->pages[i]; > > > > BUG_ON(!page); > > __free_page(page); > > } > > > > is it possible that nr_pages is a huge number (a large vmalloc area)? I > > do not see any cond_resched down __free_page path at least. vfree > > delayes the call to workqueue when called from irq context and vunmap is > > marked as might_sleep). So to me it looks like it would be safe. Something > > for vmalloc familiar people, though. > > > > Anyway, the loop seems to be there since ages so I guess somebody just > > started calling vmalloc for huge areas recently so it shown up. > > I might be missing something obvious here, but why does that loop exists at all? > > Can't we just call __free_pages() instead? This is vmalloc so the pages are not necessarily physically contiguous, no? -- Michal Hocko SUSE Labs -- 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/ . Don't email: email@kvack.org