[CRIU] [PATCH 08/22] parasite: Prepare structures for daemon mode

[Andrew Vagin]

On Wed, May 08, 2013 at 05:28:35PM +0400, Andrey Vagin wrote:
> From: Cyrill Gorcunov <gorcunov at openvz.org>
> 
> Parasite daemon mode might be considered as a series
> of network messages sent from main crtools module to
> parasite daemon which spins on a socket waiting for
> command to handle.
> 
> Simple command handling session might look as
> 
>         crtools                     daemon
>         |                           |                           |
>         | ---> command message ---> |                           |
>         |                           | ---> receive command ---> |
>         |                           |           ....            |
>         |                           |       handle command      |
>         |                           |           ....            |
>         |                           | <--- send ack       <---  |
>         | <--- receive ack     <--- |                           |
>         |                           |                           |
>         v                           v                           v
>       time
> 
> where, in case of multithread application [handle command] stage
> includes waking up of children threads via futexes, wait until
> handling complete and only then send ack back to ctrools module.
> 
> This patch brings in description of command message as
> 
> struct ctl_msg {
>     unsigned int    id;     /* command recipient */
>     unsigned int    cmd;    /* command itself */
>     unsigned int    ack;    /* ack on command */
>     int             err;    /* error code on reply */
> };
> 
> For example, in case of dumpee being with pid 2 and acquiring
> to handle PARASITE_CMD_DUMP_MISC, the command/ack series will look
> as
> 
>     cmd-msg
>     -------
>     .id     = 2,
>     .cmd    = PARASITE_CMD_DUMP_MISC,
>     .ack    = 0,
>     .err    = 0,
> 
>     ack-msg
>     -------
>     .id     = 2,
>     .cmd    = PARASITE_CMD_DUMP_MISC,
>     .ack    = PARASITE_CMD_DUMP_MISC,
>     .err    = 0
> 
> in case if error happened in parasite, the @err field set accordingly.
> 
> For convenience ctl_msg_cmd()/ctl_msg_ack() macros are provided
> for control message generations.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  include/parasite.h | 23 +++++++++++++++++++++++
>  pie/parasite.c     |  6 ++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/include/parasite.h b/include/parasite.h
> index 72a4b40..421dad3 100644
> --- a/include/parasite.h
> +++ b/include/parasite.h
> @@ -18,8 +18,18 @@
>  #define __head __used __section(.head.text)
>  
>  enum {
> +	PARASITE_CMD_IDLE		= 0,
> +	PARASITE_CMD_ACK,
> +
>  	PARASITE_CMD_INIT,
>  	PARASITE_CMD_INIT_THREAD,
> +
> +	/*
> +	 * These two must be greater than INITs.
> +	 */
> +	PARASITE_CMD_DAEMONIZE,
> +	PARASITE_CMD_DAEMONIZED,

Looks like PARASITE_CMD_DAEMONIZED is not required.

> +
>  	PARASITE_CMD_CFG_LOG,
>  	PARASITE_CMD_FINI,
>  	PARASITE_CMD_FINI_THREAD,
> @@ -39,6 +49,19 @@ enum {
>  	PARASITE_CMD_MAX,
>  };
>  
> +struct ctl_msg {
> +	unsigned int	id;			/* command recipient */
> +	unsigned int	cmd;			/* command itself */
> +	unsigned int	ack;			/* ack on command */
> +	int		err;			/* error code on reply */
> +};
> +
> +#define ctl_msg_cmd(_id, _cmd)		\
> +	(struct ctl_msg){ .id = _id, .cmd = _cmd, }
> +
> +#define ctl_msg_ack(_id, _cmd, _err)	\
> +	(struct ctl_msg){ .id = _id, .cmd = _cmd, .ack = _cmd, .err = _err, }
> +
>  struct parasite_init_args {
>  	int			h_addr_len;
>  	struct sockaddr_un	h_addr;
> diff --git a/pie/parasite.c b/pie/parasite.c
> index 82a4c3d..972d9a5 100644
> --- a/pie/parasite.c
> +++ b/pie/parasite.c
> @@ -8,6 +8,7 @@
>  
>  #include "syscall.h"
>  #include "parasite.h"
> +#include "lock.h"
>  #include "log.h"
>  
>  #include <string.h>
> @@ -19,6 +20,11 @@ static int tsock = -1;
>  static struct tid_state_s {
>  	pid_t		real;
>  	pid_t		tid;
> +
> +	futex_t		cmd;
> +	futex_t		ack;
> +	int		ret;
> +
>  	bool		use_sig_blocked;
>  	k_rtsigset_t	sig_blocked;
>  	void		*next;
> -- 
> 1.8.2
>