pid: Implement PIDTYPE_TGID

Everywhere except in the pid array we distinguish between a tasks pid and
a tasks tgid (thread group id).  Even in the enumeration we want that
distinction sometimes so we have added __PIDTYPE_TGID.  With leader_pid
we almost have an implementation of PIDTYPE_TGID in struct signal_struct.

Add PIDTYPE_TGID as a first class member of the pid_type enumeration and
into the pids array.  Then remove the __PIDTYPE_TGID special case and the
leader_pid in signal_struct.

The net size increase is just an extra pointer added to struct pid and
an extra pair of pointers of an hlist_node added to task_struct.

The effect on code maintenance is the removal of a number of special
cases today and the potential to remove many more special cases as
PIDTYPE_TGID gets used to it's fullest.  The long term potential
is allowing zombie thread group leaders to exit, which will remove
a lot more special cases in the code.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2017-06-04 04:32:13 -05:00
parent 2c4704756c
commit 6883f81aac
14 changed files with 19 additions and 19 deletions

View file

@ -67,7 +67,7 @@ void foo(void)
DEFINE(IA64_SIGNAL_GROUP_STOP_COUNT_OFFSET,offsetof (struct signal_struct,
group_stop_count));
DEFINE(IA64_SIGNAL_SHARED_PENDING_OFFSET,offsetof (struct signal_struct, shared_pending));
DEFINE(IA64_SIGNAL_LEADER_PID_OFFSET, offsetof (struct signal_struct, leader_pid));
DEFINE(IA64_SIGNAL_PIDS_TGID_OFFSET, offsetof (struct signal_struct, pids[PIDTYPE_TGID]));
BLANK();

View file

@ -68,10 +68,10 @@ ENTRY(fsys_getpid)
add r9=TI_FLAGS+IA64_TASK_SIZE,r16
;;
ld4 r9=[r9]
add r17=IA64_SIGNAL_LEADER_PID_OFFSET,r17
add r17=IA64_SIGNAL_PIDS_TGID_OFFSET,r17
;;
and r9=TIF_ALLWORK_MASK,r9
ld8 r17=[r17] // r17 = current->signal->leader_pid
ld8 r17=[r17] // r17 = current->signal->pids[PIDTYPE_TGID]
;;
add r8=IA64_PID_LEVEL_OFFSET,r17
;;

View file

@ -665,7 +665,7 @@ static void cpumsf_output_event_pid(struct perf_event *event,
goto out;
/* Update the process ID (see also kernel/events/core.c) */
data->tid_entry.pid = cpumsf_pid_type(event, pid, __PIDTYPE_TGID);
data->tid_entry.pid = cpumsf_pid_type(event, pid, PIDTYPE_TGID);
data->tid_entry.tid = cpumsf_pid_type(event, pid, PIDTYPE_PID);
perf_output_sample(&handle, &header, data, event);

View file

@ -1146,6 +1146,7 @@ static int de_thread(struct task_struct *tsk)
*/
tsk->pid = leader->pid;
change_pid(tsk, PIDTYPE_PID, task_pid(leader));
transfer_pid(leader, tsk, PIDTYPE_TGID);
transfer_pid(leader, tsk, PIDTYPE_PGID);
transfer_pid(leader, tsk, PIDTYPE_SID);

View file

@ -7,11 +7,10 @@
enum pid_type
{
PIDTYPE_PID,
PIDTYPE_TGID,
PIDTYPE_PGID,
PIDTYPE_SID,
PIDTYPE_MAX,
/* only valid to __task_pid_nr_ns() */
__PIDTYPE_TGID
};
/*

View file

@ -1275,12 +1275,12 @@ static inline pid_t task_session_vnr(struct task_struct *tsk)
static inline pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, ns);
return __task_pid_nr_ns(tsk, PIDTYPE_TGID, ns);
}
static inline pid_t task_tgid_vnr(struct task_struct *tsk)
{
return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, NULL);
return __task_pid_nr_ns(tsk, PIDTYPE_TGID, NULL);
}
static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns)

View file

@ -147,7 +147,6 @@ struct signal_struct {
#endif
/* PID/PID hash table linkage. */
struct pid *leader_pid;
struct pid *pids[PIDTYPE_MAX];
#ifdef CONFIG_NO_HZ_FULL
@ -571,7 +570,7 @@ struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
static inline struct pid *task_tgid(struct task_struct *task)
{
return task->signal->leader_pid;
return task->signal->pids[PIDTYPE_TGID];
}
/*
@ -607,7 +606,7 @@ static inline bool thread_group_leader(struct task_struct *p)
*/
static inline bool has_group_leader_pid(struct task_struct *p)
{
return task_pid(p) == p->signal->leader_pid;
return task_pid(p) == task_tgid(p);
}
static inline

View file

@ -33,9 +33,9 @@ static struct signal_struct init_signals = {
},
#endif
INIT_CPU_TIMERS(init_signals)
.leader_pid = &init_struct_pid,
.pids = {
[PIDTYPE_PID] = &init_struct_pid,
[PIDTYPE_TGID] = &init_struct_pid,
[PIDTYPE_PGID] = &init_struct_pid,
[PIDTYPE_SID] = &init_struct_pid,
},

View file

@ -1334,7 +1334,7 @@ static u32 perf_event_pid_type(struct perf_event *event, struct task_struct *p,
static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
{
return perf_event_pid_type(event, p, __PIDTYPE_TGID);
return perf_event_pid_type(event, p, PIDTYPE_TGID);
}
static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)

View file

@ -73,6 +73,7 @@ static void __unhash_process(struct task_struct *p, bool group_dead)
nr_threads--;
detach_pid(p, PIDTYPE_PID);
if (group_dead) {
detach_pid(p, PIDTYPE_TGID);
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);

View file

@ -1946,6 +1946,7 @@ static __latent_entropy struct task_struct *copy_process(
init_task_pid(p, PIDTYPE_PID, pid);
if (thread_group_leader(p)) {
init_task_pid(p, PIDTYPE_TGID, pid);
init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
init_task_pid(p, PIDTYPE_SID, task_session(current));
@ -1954,7 +1955,6 @@ static __latent_entropy struct task_struct *copy_process(
p->signal->flags |= SIGNAL_UNKILLABLE;
}
p->signal->leader_pid = pid;
p->signal->tty = tty_kref_get(current->signal->tty);
/*
* Inherit has_child_subreaper flag under the same
@ -1965,6 +1965,7 @@ static __latent_entropy struct task_struct *copy_process(
p->real_parent->signal->is_child_subreaper;
list_add_tail(&p->sibling, &p->real_parent->children);
list_add_tail_rcu(&p->tasks, &init_task.tasks);
attach_pid(p, PIDTYPE_TGID);
attach_pid(p, PIDTYPE_PGID);
attach_pid(p, PIDTYPE_SID);
__this_cpu_inc(process_counts);

View file

@ -269,8 +269,6 @@ static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type)
{
return (type == PIDTYPE_PID) ?
&task->thread_pid :
(type == __PIDTYPE_TGID) ?
&task->signal->leader_pid :
&task->signal->pids[type];
}

View file

@ -139,9 +139,10 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
{
struct signal_struct *sig =
container_of(timer, struct signal_struct, real_timer);
struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
return HRTIMER_NORESTART;
}

View file

@ -895,7 +895,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
trace_itimer_expire(signo == SIGPROF ?
ITIMER_PROF : ITIMER_VIRTUAL,
tsk->signal->leader_pid, cur_time);
task_tgid(tsk), cur_time);
__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
}