From owner-freebsd-current@FreeBSD.ORG Wed Jun 20 12:26:23 2012 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id D4C16106567A; Wed, 20 Jun 2012 12:26:23 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from bigwig.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net [IPv6:2001:470:1f10:75::2]) by mx1.freebsd.org (Postfix) with ESMTP id A9D448FC12; Wed, 20 Jun 2012 12:26:23 +0000 (UTC) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 16B7AB96E; Wed, 20 Jun 2012 08:26:23 -0400 (EDT) From: John Baldwin To: Alan Cox Date: Wed, 20 Jun 2012 08:19:39 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p13; KDE/4.5.5; amd64; ; ) References: <4FE127D3.8070502@FreeBSD.org> In-Reply-To: <4FE127D3.8070502@FreeBSD.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201206200819.39256.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Wed, 20 Jun 2012 08:26:23 -0400 (EDT) Cc: Steve Wills , Konstantin Belousov , current@freebsd.org Subject: Re: panic with out of memory X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 20 Jun 2012 12:26:24 -0000 On Tuesday, June 19, 2012 9:30:59 pm Steve Wills wrote: > Hi, > > I just got a panic out of my r237195 system. The panic looks like: > > Sleeping thread (tid 173153, pid 42034) owns a non-sleepable lock > KDB: stack backtrace of thread 173153: > sched_switch() at sched_switch+0x28a > mi_switch() at mi_switch+0xdf > sleepq_timedwait() at sleepq_timedwait+0x3a > _sleep() at _sleep+0x266 > swp_pager_meta_build() at swp_pager_meta_build+0x259 > swap_pager_copy() at swap_pager_copy+0x17b > vm_object_collapse() at vm_object_collapse+0x123 > vm_object_deallocate() at vm_object_deallocate+0x457 > vm_map_process_deferred() at vm_map_process_deferred+0x72 > vm_pageout_oom() at vm_pageout_oom+0x180 > swp_pager_meta_build() at swp_pager_meta_build+0x248 > swap_pager_copy() at swap_pager_copy+0x17b > vm_object_collapse() at vm_object_collapse+0x123 > vm_object_deallocate() at vm_object_deallocate+0x457 > vm_map_process_deferred() at vm_map_process_deferred+0x72 > vm_map_remove() at vm_map_remove+0x116 > exec_new_vmspace() at exec_new_vmspace+0x1bc > exec_elf64_imgact() at exec_elf64_imgact+0x5f4 > kern_execve() at kern_execve+0x6f0 > sys_execve() at sys_execve+0x37 > amd64_syscall() at amd64_syscall+0x351 > Xfast_syscall() at Xfast_syscall+0xfb > --- syscall (59, FreeBSD ELF64, sys_execve), rip = 0x800d2eddc, rsp = > 0x7fffffffd328, rbp = 0x7fffffffd470 --- > panic: sleeping thread > cpuid = 4 > > The system was very busy and using lots of swap, but I didn't expect a > panic. If any more detail is needed or I should just get more RAM, let > me know. :) Hmm, this is due to a bug I noticed recently as well. I had been talking with Alan and Konstantin about the proper fix. Hmm, thinking abou this some more, perhaps a simpler fix would be to have a 'I'm already in vm_map_process_deferred()' flag. Or even better, just move the entire list off into a static variable so that we don't get caught in recursion. Something like this: Index: vm_map.c =================================================================== --- vm_map.c (revision 237227) +++ vm_map.c (working copy) @@ -475,12 +475,14 @@ static void vm_map_process_deferred(void) { struct thread *td; - vm_map_entry_t entry; + vm_map_entry_t entry, next; vm_object_t object; td = curthread; - while ((entry = td->td_map_def_user) != NULL) { - td->td_map_def_user = entry->next; + entry = td->td_map_def_user; + td->td_map_def_user = NULL; + while (entry != NULL) { + next = entry->next; if ((entry->eflags & MAP_ENTRY_VN_WRITECNT) != 0) { /* * Decrement the object's writemappings and @@ -494,6 +496,7 @@ vm_map_process_deferred(void) entry->end); } vm_map_entry_deallocate(entry, FALSE); + entry = next; } } -- John Baldwin