From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756978AbZFOIdM (ORCPT ); Mon, 15 Jun 2009 04:33:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751689AbZFOIc7 (ORCPT ); Mon, 15 Jun 2009 04:32:59 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:42521 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750964AbZFOIc7 (ORCPT ); Mon, 15 Jun 2009 04:32:59 -0400 Subject: Re: [GIT PULL v2] Early SLAB fixes for 2.6.31 From: Pekka Enberg To: Nick Piggin Cc: Heiko Carstens , torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, cl@linux-foundation.org, kamezawa.hiroyu@jp.fujitsu.com, lizf@cn.fujitsu.com, mingo@elte.hu, yinghai@kernel.org, benh@kernel.crashing.org In-Reply-To: <20090615082636.GA30964@wotan.suse.de> References: <20090615081831.GA5411@osiris.boeblingen.de.ibm.com> <20090615082636.GA30964@wotan.suse.de> Date: Mon, 15 Jun 2009 11:32:59 +0300 Message-Id: <1245054779.23207.6.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit X-Mailer: Evolution 2.24.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Nick, On Mon, 2009-06-15 at 10:26 +0200, Nick Piggin wrote: > On Mon, Jun 15, 2009 at 10:18:31AM +0200, Heiko Carstens wrote: > > On Fri, Jun 12, 2009 at 07:16:30PM +0300, Pekka J Enberg wrote: > > > Hi Linus, > > > > > > I dropped the GFP_WAIT conversion patch and added the gfp masking patch > > > you liked. I tested this on x86-64 with both SLAB and SLUB. > > > > Hi Pekka, > > > > I tried to convert some of the early allocations on s390. Some callsites > > however need to have the GFP_DMA flag, since we need to allocate memory below > > 2GB. Passing GFP_DMA causes this crash: > > > > <1>Unable to handle kernel pointer dereference at virtual kernel address fffffffffffff000 > > <4>Oops: 0038 [#1] PREEMPT SMP > > <4>Modules linked in: > > <4>CPU: 0 Not tainted 2.6.30-03984-g45e3e19-dirty #233 > > <4>Process swapper (pid: 0, task: 00000000006a2ef0, ksp: 0000000000718000) > > <4>Krnl PSW : 0700100180000000 00000000000808ee (queue_work_on+0x8e/0xe0) > > <4> R:0 T:1 IO:1 EX:1 Key:0 M:0 W:0 P:0 AS:0 CC:1 PM:0 EA:3 > > <4>Krnl GPRS: 0000000000000000 ffffffffffffffff 0000000000000000 00000000006b8b88 > > <4> 00000000006b8b88 0000000000000001 0000000000000008 0000000000000200 > > <4> 000000003fe28000 0000000000008001 00000000011da730 0000000000717ca0 > > <4> 00000000006b8b88 0000000000488650 0000000000717cd0 0000000000717ca0 > > <4>Krnl Code: 00000000000808de: e310d0000082 xg %r1,0(%r13) > > <4> 00000000000808e4: eb220003000d sllg %r2,%r2,3 > > <4> 00000000000808ea: b9040034 lgr %r3,%r4 > > <4> >00000000000808ee: e32210000004 lg %r2,0(%r2,%r1) > > <4> 00000000000808f4: c0e5ffffff28 brasl %r14,80744 > > <4> 00000000000808fa: a7280001 lhi %r2,1 > > <4> 00000000000808fe: e340b0b80004 lg %r4,184(%r11) > > <4> 0000000000080904: b9140022 lgfr %r2,%r2 > > <4>Call Trace: > > <4>([<000000003fe28000>] 0x3fe28000) > > <4> [<0000000000080e96>] queue_work+0x62/0xa4 > > <4> [<0000000000080f26>] schedule_work+0x4e/0x60 > > <4> [<0000000000132f7e>] dma_kmalloc_cache+0x1ca/0x1d0 > > <4> [<00000000001330ae>] get_slab+0x12a/0x130 > > <4> [<00000000001337b6>] __kmalloc+0x5e/0x364 > > <4> [<0000000000739132>] con3215_init+0x1c2/0x2e4 > > <4> [<00000000007333ea>] console_init+0x42/0x5c > > <4> [<0000000000718e50>] start_kernel+0x53c/0x6b8 > > <4> [<0000000000012020>] _ehead+0x20/0x80 > > > > I didn't look any deeper into this, but looks to me like doing something like > > schedule_work() this early isn't ok. > > > > This is the conversion that leads to the crash: > > > > - alloc_bootmem_low(sizeof(struct raw3215_info)); > > + kzalloc(sizeof(struct raw3215_info), GFP_NOWAIT | GFP_DMA); > > > > Might be that I missed something. Maybe some special flag? > > No, just a bug in the conversion. > > If you predicate the schedule_work call on slab_state == SYSFS, then > it should work (when sysfs comes up later in init, previously added > slabs will be registered with sysfs). > > Oh, and you'd need to also not pass __SYSFS_ADD_DEFERRED into > kmem_cache_create in that case too. I am not sure I follow you here. We are setting up slab so early that we absolutely _must_ defer sysfs setup. But we're also setting up slab much earlier than workqueues, so we shouldn't really do schedule_work() at that point. Furthermore, early boot cache sysfs setup is explicitly handled in slab_sysfs_init() so I think we need something like the patch below? Pekka diff --git a/mm/slub.c b/mm/slub.c index 30354bf..4c12138 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2642,7 +2642,13 @@ static noinline struct kmem_cache *dma_kmalloc_cache(int index, gfp_t flags) list_add(&s->list, &slab_caches); kmalloc_caches_dma[index] = s; - schedule_work(&sysfs_add_work); + /* + * The slab allocator is set up much earlier than workqueues. As early + * boot caches are handle by slab_sysfs_init(), avoid calling + * schedule_work() until keventd is up. + */ + if (keventd_up()) + schedule_work(&sysfs_add_work); unlock_out: up_write(&slub_lock);