From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx126.postini.com [74.125.245.126]) by kanga.kvack.org (Postfix) with SMTP id 13BE46B0032 for ; Mon, 16 Sep 2013 17:28:02 -0400 (EDT) Message-ID: <523777D8.2000304@jp.fujitsu.com> Date: Mon, 16 Sep 2013 17:27:52 -0400 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [RESEND PATCH v5 4/4] mm/vmalloc: fix show vmap_area information race with vmap_area tear down References: <1379202342-23140-1-git-send-email-liwanp@linux.vnet.ibm.com> <1379202342-23140-4-git-send-email-liwanp@linux.vnet.ibm.com> In-Reply-To: <1379202342-23140-4-git-send-email-liwanp@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: liwanp@linux.vnet.ibm.com Cc: akpm@linux-foundation.org, iamjoonsoo.kim@lge.com, rientjes@google.com, kosaki.motohiro@jp.fujitsu.com, zhangyanfei@cn.fujitsu.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 9/14/2013 7:45 PM, Wanpeng Li wrote: > Changelog: > *v4 -> v5: return directly for !VM_VM_AREA case and remove (VM_LAZY_FREE | VM_LAZY_FREEING) check > > There is a race window between vmap_area tear down and show vmap_area information. > > A B > > remove_vm_area > spin_lock(&vmap_area_lock); > va->vm = NULL; > va->flags &= ~VM_VM_AREA; > spin_unlock(&vmap_area_lock); > spin_lock(&vmap_area_lock); > if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEZING)) > return 0; > if (!(va->flags & VM_VM_AREA)) { > seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n", > (void *)va->va_start, (void *)va->va_end, > va->va_end - va->va_start); > return 0; > } > free_unmap_vmap_area(va); > flush_cache_vunmap > free_unmap_vmap_area_noflush > unmap_vmap_area > free_vmap_area_noflush > va->flags |= VM_LAZY_FREE > > The assumption !VM_VM_AREA represents vm_map_ram allocation is introduced by > commit: d4033afd(mm, vmalloc: iterate vmap_area_list, instead of vmlist, in > vmallocinfo()). However, !VM_VM_AREA also represents vmap_area is being tear > down in race window mentioned above. This patch fix it by don't dump any > information for !VM_VM_AREA case and also remove (VM_LAZY_FREE | VM_LAZY_FREEING) > check since they are not possible for !VM_VM_AREA case. > > Suggested-by: Joonsoo Kim > Signed-off-by: Wanpeng Li Acked-by: KOSAKI Motohiro -- 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