[CRIU] [PATCH 01/12] pstree: Bind CoreEntry to pstree and fill it with registers early

[Pavel Emelyanov]

On 02/28/2013 07:35 PM, Cyrill Gorcunov wrote:
> 
> When parasite daemon mode will be implemented we get deprived of ability
> to fetch registers at the late moment of dumping as we were, thus just
> bind CoreEntry to pstree item and allocate CoreEntry'ies for every
> thread found, once process tree is in seized state.
> 
> Then immediately fill CoreEntry'ies with registers. We use prctl
> opcode for that but fetch a complete set of registers including
> FPU state, and convert them into protobuf format.
> 
> Zombie tasks remains untouched, we allocate CoreEntry for them
> right at moment of dumping becuase we don't need registers there
> to be written on disk.
> 
> This way get_task_regs no longer need parasite_ctl argument
> and it's zapped.
> 
> Still parasite_ctl has own copy of general registers set but
> this is because we need them to be in cpu native format unlike
> ones kept in CoreEntry.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  arch/arm/crtools.c          |  12 ++---
>  arch/arm/include/asm/dump.h |   2 +-
>  arch/x86/crtools.c          |  12 ++---
>  arch/x86/include/asm/dump.h |   2 +-
>  cr-dump.c                   | 119 +++++++++++++++++---------------------------
>  include/pstree.h            |   5 ++
>  pstree.c                    |  70 ++++++++++++++++++++++++++
>  7 files changed, 131 insertions(+), 91 deletions(-)
> 


> -	if (ctl)
> -		regs = ctl->regs_orig;
> -	else {
> -		if (ptrace(PTRACE_GETREGS, pid, NULL, &regs)) {
> -			pr_err("Can't obtain GP registers for %d\n", pid);
> -			goto err;
> -		}
> +	if (ptrace(PTRACE_GETREGS, pid, NULL, &regs)) {
> +		pr_err("Can't obtain GP registers for %d\n", pid);
> +		goto err;
>  	}

So, do we still have regs duplication?

> +static int collect_regs_seized(struct pstree_item *item)
> +{
> +	unsigned int i;
> +	int ret;
> +
> +	if (pstree_alloc_cores(item))
> +		return -1;
> +
> +	for (i = 0; i < item->nr_threads; i++) {
> +		pid_t pid = item->threads[i].real;
> +		ret = get_task_regs(pid, item->core[i]);
> +		if (ret) {
> +			pr_err("Can't obtain regs for thread %d\n", pid);
> +			return -1;
> +		}
> +
> +		if (item->threads[i].real == item->pid.real)
> +			item->this_core = item->core[i];

We've already done this in pstree_alloc_cores()

> +	}
> +
> +	return 0;
> +}

> +int pstree_alloc_cores(struct pstree_item *item)
> +{
> +	unsigned int i;
> +
> +	item->core = xzalloc(sizeof(*item->core) * item->nr_threads);
> +	if (!item->core)
> +		return -1;
> +
> +	for (i = 0; i < item->nr_threads; i++) {
> +		int is_leader = (item->threads[i].real == item->pid.real);
> +
> +		item->core[i] = core_entry_alloc(item->state != TASK_DEAD, is_leader);
> +		if (!item->core[i])
> +			goto err;
> +
> +		if (is_leader)
> +			item->this_core = item->core[i];

The version in collect_regs_seized() without is_leader looks nicer.

> +	}
> +
> +	return 0;
> +err:
> +	pstree_free_cores(item);
> +	return -1;
> +}
> +