Messages in this thread Patch in this message | | | Subject | Re: [RFC v2][PATCH 8/9] Remove some BUG_ON()s that need some proper error handling instead. | From | Matt Helsley <> | Date | Thu, 28 Aug 2008 21:18:02 -0700 |
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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
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