Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751694AbYH2ESS (ORCPT ); Fri, 29 Aug 2008 00:18:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750749AbYH2ESI (ORCPT ); Fri, 29 Aug 2008 00:18:08 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:43740 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750739AbYH2ESF (ORCPT ); Fri, 29 Aug 2008 00:18:05 -0400 Subject: Re: [RFC v2][PATCH 8/9] Remove some BUG_ON()s that need some proper error handling instead. From: Matt Helsley To: Dave Hansen Cc: arnd@arndb.de, jeremy@goop.org, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org In-Reply-To: <20080820192607.91E0AFF2@nimitz> References: <20080820192557.98788FAB@nimitz> <20080820192607.91E0AFF2@nimitz> Content-Type: text/plain Organization: IBM Linux Technology Center Date: Thu, 28 Aug 2008 21:18:02 -0700 Message-Id: <1219983482.11632.61.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3815 Lines: 104 On Wed, 2008-08-20 at 12:26 -0700, Dave Hansen wrote: > > > --- > > oren-cr.git-dave/checkpoint/checkpoint.c | 12 ++++++++++-- > oren-cr.git-dave/checkpoint/restart.c | 15 +++++++++++++++ > 2 files changed, 25 insertions(+), 2 deletions(-) > > diff -puN checkpoint/checkpoint.c~0002-Remove-some-BUG_ON-s-that-need-some-proper-error-ha checkpoint/checkpoint.c > --- oren-cr.git/checkpoint/checkpoint.c~0002-Remove-some-BUG_ON-s-that-need-some-proper-error-ha 2008-08-20 12:12:51.000000000 -0700 > +++ oren-cr.git-dave/checkpoint/checkpoint.c 2008-08-20 12:12:51.000000000 -0700 > @@ -125,7 +125,8 @@ static int cr_write_tail(struct cr_ctx * > h.id = 0; > > hh->magic = CR_HEADER_MAGIC; > - hh->cksum[0] = hh->cksum[1] = 1; /* TBD ... */ > + hh->cksum[0] = 1; > + hh->cksum[1] = 1; /* TBD ... */ > > ret = cr_write_obj(ctx, &h, hh); > kfree(hh); > @@ -183,7 +184,14 @@ static int cr_write_task(struct cr_ctx * > { > int ret ; > > - BUG_ON(t->state == TASK_DEAD); > + /* > + * This was a BUG_ON(), which kinda makes sense if you > + * are only allowing checkpointing of 'current'. But, > + * it is still pretty silly in that case. Make it > + * something a bit more sensible. > + */ > + if (t->state == TASK_DEAD) > + return -EAGAIN; This is OK for a debug patch but I think in the end we'd want to do something similar early in sys_checkpoint -- before we start writing anything. We should check to ensure the task is properly frozen there and return -EBUSY if not frozen. Something like: /* Only current can self-checkpoint. Everything else must be frozen first. */ for_each_task_being_checkpointed(t) { if ((t != current) && !is_task_frozen_enough(t)) return -EBUSY; } is_task_frozen_enough() current lives in kernel/cgroup_freezer.c. I think it can easily be pulled out of the cgroup_freezer.c code so that we don't introduce a CONFIG dependency... > ret = cr_write_task_struct(ctx, t); > pr_debug("ret (task_struct) %d\n", ret); > diff -puN checkpoint/restart.c~0002-Remove-some-BUG_ON-s-that-need-some-proper-error-ha checkpoint/restart.c > --- oren-cr.git/checkpoint/restart.c~0002-Remove-some-BUG_ON-s-that-need-some-proper-error-ha 2008-08-20 12:12:51.000000000 -0700 > +++ oren-cr.git-dave/checkpoint/restart.c 2008-08-20 12:12:51.000000000 -0700 > @@ -74,6 +74,11 @@ static int cr_read_hdr(struct cr_ctx *ct > struct cr_hdr_head *hh = kmalloc(sizeof(*hh), GFP_KERNEL); > int ret; > > + if (!hh) { > + pr_debug("unable to get %d bytes from ctx buf for header\n", > + sizeof(*hh)); > + return -ENOMEM; > + } > ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_HEAD); > if (ret < 0) > return ret; > @@ -99,6 +104,11 @@ static int cr_read_tail(struct cr_ctx *c > struct cr_hdr_tail *hh = kmalloc(sizeof(*hh), GFP_KERNEL); > int ret; > > + if (!hh) { > + pr_debug("unable to get %d bytes from ctx buf for tail\n", > + sizeof(*hh)); > + return -ENOMEM; > + } > ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_TAIL); > if (ret < 0) > return ret; > @@ -118,6 +128,11 @@ static int cr_read_task_struct(struct cr > struct task_struct *t = current; > int ret; > > + if (!hh) { > + pr_debug("unable to get %d bytes from ctx buf for task\n", > + sizeof(*hh)); > + return -ENOMEM; > + } > ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_TASK); > if (ret < 0) > return ret; > _ > _______________________________________________ > Containers mailing list > Containers@lists.linux-foundation.org > https://lists.linux-foundation.org/mailman/listinfo/containers -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/