From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kornilios Kourtis Subject: Re: [BUG] Invalid return address of mmap() followed by mbind() in multithreaded context Date: Mon, 27 Jun 2011 20:18:42 +0300 Message-ID: <20110627171842.GA7554@solar.cslab.ece.ntua.gr> References: <4DFB710D.7000902@cslab.ece.ntua.gr> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <4DFB710D.7000902@cslab.ece.ntua.gr> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Vasileios Karakasis , KOSAKI Motohiro Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-numa@vger.kernel.org Hi, On Fri, Jun 17, 2011 at 06:21:49PM +0300, Vasileios Karakasis wrote: > Hi, > > I am implementing a multithreaded numa aware code where each thread > mmap()'s an anonymous private region and then mbind()'s it to its local > node. The threads are performing a series of such mmap() + mbind() > operations. My program crashed with SIGSEGV and I noticed that mmap() > returned an invalid address. I've taken a closer look at this issue. As Vasileios said, it can be reproduced by having two threads doing the following loop: | for { | addr = mmap(4096, MAP_ANONUMOUS) | if (addr == (void *)-1) | continue | mbind(addr, 4096, 0x1) // do mbind on first NUMA node | } After a couple of iterations, mbind() will return EFAULT, although the addr is valid. Doing a bisect, pins it down to the following commit (Author added to To:): 9d8cebd4bcd7c3878462fdfda34bbcdeb4df7ef4 mm: fix mbind vma merge problem Which adds merging of vmas in the mbind() path. Reverting this commit, seems to fix the issue. I 've added some printks to track down the issue, and EFAULT is returned on: mm/mempolicy.c: mbind_range() | vma = find_vma_prev(mm. start, &prev); | if (!vma |vma->vm_start > start) | return EFAULT; Where: vma->start > start I am not sure what exactly happens, but concurrent merges and splits of (already mapped) VMAs do not seem to work well together. cheers, -Kornilios -- Kornilios Kourtis -- 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