Commit 02b51df1 authored by Scott James Remnant's avatar Scott James Remnant Committed by Linus Torvalds
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proc connector: add event for process becoming session leader 



The act of a process becoming a session leader is a useful signal to a
supervising init daemon such as Upstart.

While a daemon will normally do this as part of the process of becoming a
daemon, it is rare for its children to do so.  When the children do, it is
nearly always a sign that the child should be considered detached from the
parent and not supervised along with it.

The poster-child example is OpenSSH; the per-login children call setsid()
so that they may control the pty connected to them.  If the primary daemon
dies or is restarted, we do not want to consider the per-login children
and want to respawn the primary daemon without killing the children.

This patch adds a new PROC_SID_EVENT and associated structure to the
proc_event event_data union, it arranges for this to be emitted when the
special PIDTYPE_SID pid is set.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarScott James Remnant <scott@ubuntu.com>
Acked-by: default avatarMatt Helsley <matthltc@us.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Acked-by: default avatar"David S. Miller" <davem@davemloft.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 88e9d34c

drivers/connector/cn_proc.c

+25 −0
Original line number Diff line number Diff line
@@ -139,6 +139,31 @@ void proc_id_connector(struct task_struct *task, int which_id) 
	cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);

}



void proc_sid_connector(struct task_struct *task)

{

	struct cn_msg *msg;

	struct proc_event *ev;

	struct timespec ts;

	__u8 buffer[CN_PROC_MSG_SIZE];



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	ev = (struct proc_event *)msg->data;

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->what = PROC_EVENT_SID;

	ev->event_data.sid.process_pid = task->pid;

	ev->event_data.sid.process_tgid = task->tgid;



	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));

	msg->ack = 0; /* not used */

	msg->len = sizeof(*ev);

	cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);

}



void proc_exit_connector(struct task_struct *task)

{

	struct cn_msg *msg;

include/linux/cn_proc.h

+10 −0
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ struct proc_event { 
		PROC_EVENT_EXEC = 0x00000002,

		PROC_EVENT_UID  = 0x00000004,

		PROC_EVENT_GID  = 0x00000040,

		PROC_EVENT_SID  = 0x00000080,

		/* "next" should be 0x00000400 */

		/* "last" is the last process event: exit */

		PROC_EVENT_EXIT = 0x80000000
@@ -89,6 +90,11 @@ struct proc_event { 
			} e;

		} id;



		struct sid_proc_event {

			__kernel_pid_t process_pid;

			__kernel_pid_t process_tgid;

		} sid;



		struct exit_proc_event {

			__kernel_pid_t process_pid;

			__kernel_pid_t process_tgid;
@@ -102,6 +108,7 @@ struct proc_event { 
void proc_fork_connector(struct task_struct *task);

void proc_exec_connector(struct task_struct *task);

void proc_id_connector(struct task_struct *task, int which_id);

void proc_sid_connector(struct task_struct *task);

void proc_exit_connector(struct task_struct *task);

#else

static inline void proc_fork_connector(struct task_struct *task)
@@ -114,6 +121,9 @@ static inline void proc_id_connector(struct task_struct *task, 
				     int which_id)

{}



static inline void proc_sid_connector(struct task_struct *task)

{}



static inline void proc_exit_connector(struct task_struct *task)

{}

#endif	/* CONFIG_PROC_EVENTS */

kernel/exit.c

+3 −1
Original line number Diff line number Diff line
@@ -359,8 +359,10 @@ void __set_special_pids(struct pid *pid) 
{

	struct task_struct *curr = current->group_leader;



	if (task_session(curr) != pid)

	if (task_session(curr) != pid) {

		change_pid(curr, PIDTYPE_SID, pid);

		proc_sid_connector(curr);

	}



	if (task_pgrp(curr) != pid)

		change_pid(curr, PIDTYPE_PGID, pid);

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