[Devel] Re: [PATCH] c/r: [signal 3/3] pending signals (private, shared)

[Louis Rilling]

Hi Oren,

On 23/07/09 10:48 -0400, Oren Laadan wrote:
> This patch adds checkpoint and restart of pending signals queues:
> struct sigpending, both per-task t->sigpending and shared (per-
> thread-group) t->signal->shared_sigpending.
> 
> To checkpoint pending signals (private/shared) we first detach the
> signal queue (and copy the mask) to a separate struct sigpending.
> This separate structure can be iterated through without locking.
> 
> Once the state is saved, we re-attaches (prepends) the original signal
> queue back to the original struct sigpending.
> 
> Signals that arrive(d) in the meantime will be suitably queued after
> these (for real-time signals). Repeated non-realtime signals will not
> be queued because they will already be marked in the pending mask,
> that remains as is. This is the expected behavior of non-realtime
> signals.
> 
> Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>
> ---
>  checkpoint/signal.c            |  255 +++++++++++++++++++++++++++++++++++++++-
>  include/linux/checkpoint_hdr.h |   23 ++++
>  2 files changed, 277 insertions(+), 1 deletions(-)
> 
> diff --git a/checkpoint/signal.c b/checkpoint/signal.c
> index b3f1d3e..940cc4a 100644
> --- a/checkpoint/signal.c
> +++ b/checkpoint/signal.c

[...]

> +
> +static int restore_sigpending(struct ckpt_ctx *ctx, struct sigpending *pending)
> +{
> +	struct ckpt_hdr_sigpending *h;
> +	struct ckpt_hdr_siginfo *si;
> +	struct sigqueue *q, *n;
> +	int ret = 0;
> +
> +	h = ckpt_read_buf_type(ctx, 0, CKPT_HDR_SIGPENDING);
> +	if (IS_ERR(h))
> +		return PTR_ERR(h);
> +
> +	INIT_LIST_HEAD(&pending->list);
> +	load_sigset(&pending->signal, &h->signal);
> +
> +	si = h->siginfo;
> +	while (h->nr_pending--) {
> +		q = sigqueue_alloc();

This introduces a memory leak, since collect_signal() won't free q. Better to
use __sigqueue_alloc() here, or clear the SIGQUEUE_PREALLOC flag.

Thanks,

Louis

> +		if (!q) {
> +			ret = -ENOMEM;
> +			break;
> +		}
> +
> +		ret = load_siginfo(&q->info, si++);
> +		if (ret < 0) {
> +			sigqueue_free(q);
> +			break;
> +		}
> +
> +		list_add_tail(&pending->list, &q->list);
> +	}
> +
> +	if (ret < 0) {
> +		list_for_each_entry_safe(q, n, &pending->list, list) {
> +			list_del_init(&q->list);
> +			sigqueue_free(q);
> +		}
> +	}
> +
> +	ckpt_hdr_put(ctx, h);
> +	return ret;
> +}
> +

[...]

-- 
Dr Louis Rilling			Kerlabs
Skype: louis.rilling			Batiment Germanium
Phone: (+33|0) 6 80 89 08 23		80 avenue des Buttes de Coesmes
http://www.kerlabs.com/			35700 Rennes
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