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proc connector: add event for process becoming session leader

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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: Scott James Remnant <scott@ubuntu.com>
Acked-by: Matt Helsley <matthltc@us.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Acked-by: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Scott James Remnant 2009-09-22 16:43:44 -07:00 committed by Linus Torvalds
parent 88e9d34c72
commit 02b51df1b0
3 changed files with 38 additions and 1 deletions
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25
drivers/connector/cn_proc.c
View file

@ -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;

10
include/linux/cn_proc.h
View file

@ -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 */

4
kernel/exit.c
View file

@ -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);