[Devel] Re: [RFC v2][PATCH 01/10] Infrastructure for work postponed to the end of checkpoint/restart

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at cs.columbia.edu):
> 
> 
> Serge E. Hallyn wrote:
> > Quoting Oren Laadan (orenl at cs.columbia.edu):
> >> --- a/checkpoint/Makefile
> >> +++ b/checkpoint/Makefile
> >> @@ -2,8 +2,8 @@
> >>  # Makefile for linux checkpoint/restart.
> >>  #
> >>
> >> -obj-$(CONFIG_CHECKPOINT) += sys.o objhash.o \
> >> +obj-$(CONFIG_CHECKPOINT) += sys.o objhash.o deferqueue.o \
> >>  		checkpoint.o restart.o \
> >>  		ckpt_task.o rstr_task.o \
> >>  		ckpt_mem.o rstr_mem.o \
> >> -		ckpt_file.o rstr_file.o
> >> +		ckpt_file.o rstr_file.o \
> > 
> > ?
> > 
> >> +int cr_deferqueue_add(struct cr_ctx *ctx, cr_deferqueue_func_t function,
> >> +		     unsigned int flags, void *data, int size)
> >> +{
> >> +	struct cr_deferqueue *wq;
> >> +
> >> +	wq = kmalloc(sizeof(wq) + size, GFP_KERNEL);
> >> +	if (!wq)
> >> +		return -ENOMEM;
> >> +
> >> +	wq->function = function;
> >> +	wq->flags = flags;
> >> +	memcpy(wq->data, data, size);
> >> +
> >> +	cr_debug("adding work %p function %p\n", wq, wq->function);
> >> +	list_add_tail(&ctx->deferqueue, &wq->list);
> >> +	return 0;
> >> +}
> > 
> > Shouldn't the deferqueue be protected by a spinlock here?
> 
> Not until we implement concurrent checkpoint/restart. At the moment
> it's one task at a time the can access it.

That's too bad.  I think this woudl be better done as a single
simple patch addin ga new generic deferqueue mechanism for all
to use, with a per-queue spinlock protecting both _add and
_run

-serge
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