Re: [PATCH 1/3] will_become_orphaned_pgrp: we have threads

From: Eric W. Biederman
Date: Sun Dec 09 2007 - 18:59:00 EST

Oleg Nesterov <oleg@xxxxxxxxxx> writes:

> On 12/09, Eric W. Biederman wrote:
>>
>> Equally messed up is a our status in /proc at that point. Which
>> says our sleeping process is a zombie.
>
> Yes, this is annoying.
>
>> I'm thinking we need to do at least some of the thread group leadership
>> transfer in do_exit, instead of de_thread. Then p->group_leader->exit_state
>> would be sufficient to see if the entire thread group was alive,
>> as the group_leader would be whoever was left alive. The original
>> group_leader might still need to be kept around for it's pid...
>>
>> I think that would solve most of the problems you have with a dead
>> thread group leader and sending SIG_STOP as well.
>
> Yes I was thinking about that too, but I am not brave enough to even
> try to to think to the end ;)
>
> As a minimal change, I tried to add "task_struct *leader_proxy" to
> signal_struct, which points to the next live thread, and changed by
> exit_notify(). eligible_child() checks it instead of ->exit_signal.
> But this is so messy...
>
> And in fact, if we are talking about group stop, it is a group operation,
> why do_wait() uses per-thread ->exit_code but not ->group_exit_code ?
Good question, we would need a fallback for the case it isn't a group
operation like in exit but that might clean something up.

> But yes, [PATCH 3/3] adds a visible difference, and I don't know if
> this difference is good or bad.
>
> $ sleep 1000
>
> [1]+ Stopped sleep 1000
> $ strace -p `pidof sleep`
> Process 432 attached - interrupt to quit
>
> Now strace "hangs" in do_wait() because ->exit_code was eaten by the
> shell. We need SIGCONT.
>
> With the "[PATCH 3/3]" strace proceeds happily.
>
> Oleg.

Well I got to playing with the idea of actually moving group_leader
and it turns out that while it is a pain it isn't actually that bad.
The worst part is not really changing the pid of the leader to the pid
of the entire thread group. As there are a few cases where we are
current referencing the task_pid where we really want task_tgid.

Oleg below is my proof of concept patch, which really needs to be
broken up into a whole patch series, so the changes are small
enough we can do a thorough audit on them. Anyway take a look
and see what you think.

This patch does fix your weird test case without any actual
change to the do_wait logic itself.

The key idea is that by not making PIDTYPE_PID a hash chain we
can point two different struct pids at the same process allowing
two different pids to return the same process from pid_task(pid,
PIDTYPE_PID);

Which means most things continue to just work by working on
PIDTYPE_PID, although as mentioned previously there are a few
things particulary do_notify_parent_cldstop and do_wait that
need to be changed to return the tgid instead of the pid.

Oh and in eligible child the PIDTYPE_PID test is now sneaky
essentially doing a task lookup and seeing if the result
is our target pid, instead of comparing pids.

The funny part is grep pid /proc/<tgid>/status no longer
always equals the tgid after the pid exits. Still that seems
better then making the entire thread group look like a zombie
just because the wrong thread exited.

Subject: [PATCH] All thread group leaders to exit

---
fs/exec.c | 81 ++---------------------
fs/fcntl.c | 20 ++++--
fs/proc/base.c | 6 +-
include/linux/init_task.h | 25 ++++----
include/linux/pid.h | 14 ++---
include/linux/sched.h | 43 ++++++------
kernel/exit.c | 157 +++++++++++++++++++++++++++-----------------
kernel/fork.c | 2 +-
kernel/itimer.c | 2 +-
kernel/pid.c | 60 +++++++++++------
kernel/signal.c | 23 ++-----
11 files changed, 204 insertions(+), 229 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 14a690d..1f69326 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -786,22 +786,6 @@ static int de_thread(struct task_struct *tsk)
* Account for the thread group leader hanging around:
*/
count = 1;
- if (!thread_group_leader(tsk)) {
- count = 2;
- /*
- * The SIGALRM timer survives the exec, but needs to point
- * at us as the new group leader now. We have a race with
- * a timer firing now getting the old leader, so we need to
- * synchronize with any firing (by calling del_timer_sync)
- * before we can safely let the old group leader die.
- */
- sig->tsk = tsk;
- spin_unlock_irq(lock);
- if (hrtimer_cancel(&sig->real_timer))
- hrtimer_restart(&sig->real_timer);
- spin_lock_irq(lock);
- }
-
sig->notify_count = count;
while (atomic_read(&sig->count) > count) {
__set_current_state(TASK_UNINTERRUPTIBLE);
@@ -811,68 +795,15 @@ static int de_thread(struct task_struct *tsk)
}
spin_unlock_irq(lock);

- /*
- * At this point all other threads have exited, all we have to
- * do is to wait for the thread group leader to become inactive,
- * and to assume its PID:
- */
- if (!thread_group_leader(tsk)) {
- leader = tsk->group_leader;
-
- sig->notify_count = -1;
- for (;;) {
- write_lock_irq(&tasklist_lock);
- if (likely(leader->exit_state))
- break;
- __set_current_state(TASK_UNINTERRUPTIBLE);
- write_unlock_irq(&tasklist_lock);
- schedule();
+ /* If it isn't already force gettid() == getpid() */
+ if (sig->tgid != tsk->tid) {
+ write_lock_irq(&tasklist_lock);
+ if (sig->tgid != tsk->tid) {
+ detach_pid(tsk, PIDTYPE_PID);
+ attach_pid(tsk, PIDTYPE_PID, sig->tgid);
}
-
- /*
- * The only record we have of the real-time age of a
- * process, regardless of execs it's done, is start_time.
- * All the past CPU time is accumulated in signal_struct
- * from sister threads now dead. But in this non-leader
- * exec, nothing survives from the original leader thread,
- * whose birth marks the true age of this process now.
- * When we take on its identity by switching to its PID, we
- * also take its birthdate (always earlier than our own).
- */
- tsk->start_time = leader->start_time;
-
- BUG_ON(!same_thread_group(leader, tsk));
- BUG_ON(has_group_leader_pid(tsk));
- /*
- * An exec() starts a new thread group with the
- * TGID of the previous thread group. Rehash the
- * two threads with a switched PID, and release
- * the former thread group leader:
- */
-
- /* Become a process group leader with the old leader's pid.
- * The old leader becomes a thread of the this thread group.
- * Note: The old leader also uses this pid until release_task
- * is called. Odd but simple and correct.
- */
- detach_pid(tsk, PIDTYPE_PID);
- tsk->pid = leader->pid;
- attach_pid(tsk, PIDTYPE_PID, task_pid(leader));
- transfer_pid(leader, tsk, PIDTYPE_PGID);
- transfer_pid(leader, tsk, PIDTYPE_SID);
- list_replace_rcu(&leader->tasks, &tsk->tasks);
-
- tsk->group_leader = tsk;
- leader->group_leader = tsk;
-
- tsk->exit_signal = SIGCHLD;
-
- BUG_ON(leader->exit_state != EXIT_ZOMBIE);
- leader->exit_state = EXIT_DEAD;
-
write_unlock_irq(&tasklist_lock);
}
-
sig->group_exit_task = NULL;
sig->notify_count = 0;

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 8685263..bc0a125 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -516,9 +516,13 @@ void send_sigio(struct fown_struct *fown, int fd, int band)
goto out_unlock_fown;

read_lock(&tasklist_lock);
- do_each_pid_task(pid, type, p) {
- send_sigio_to_task(p, fown, fd, band);
- } while_each_pid_task(pid, type, p);
+ if (type == PIDTYPE_PID)
+ send_sigio_to_task(pid_task(pid, type), fown, fd, band);
+ else {
+ do_each_pid_task(pid, type, p) {
+ send_sigio_to_task(p, fown, fd, band);
+ } while_each_pid_task(pid, type, p);
+ }
read_unlock(&tasklist_lock);
out_unlock_fown:
read_unlock(&fown->lock);
@@ -547,9 +551,13 @@ int send_sigurg(struct fown_struct *fown)
ret = 1;

read_lock(&tasklist_lock);
- do_each_pid_task(pid, type, p) {
- send_sigurg_to_task(p, fown);
- } while_each_pid_task(pid, type, p);
+ if (type == PIDTYPE_PID)
+ send_sigurg_to_task(pid_task(pid, type), fown);
+ else {
+ do_each_pid_task(pid, type, p) {
+ send_sigurg_to_task(p, fown);
+ } while_each_pid_task(pid, type, p);
+ }
read_unlock(&tasklist_lock);
out_unlock_fown:
read_unlock(&fown->lock);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index d59708e..f7bd620 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2438,15 +2438,15 @@ retry:
* pid of a thread_group_leader. Testing for task
* being a thread_group_leader is the obvious thing
* todo but there is a window when it fails, due to
- * the pid transfer logic in de_thread.
+ * the pid transfer logic at group leader death.
*
* So we perform the straight forward test of seeing
- * if the pid we have found is the pid of a thread
+ * if the pid we have found is the pid of the thread
* group leader, and don't worry if the task we have
* found doesn't happen to be a thread group leader.
* As we don't care in the case of readdir.
*/
- if (!iter.task || !has_group_leader_pid(iter.task)) {
+ if (!iter.task || pid != task_tgid(iter.task)) {
iter.tgid += 1;
goto retry;
}
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 96be7d6..ddcd7c1 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -67,6 +67,9 @@
.posix_timers = LIST_HEAD_INIT(sig.posix_timers), \
.cpu_timers = INIT_CPU_TIMERS(sig.cpu_timers), \
.rlim = INIT_RLIMITS, \
+ .tgid = &init_struct_pid, \
+ .pids[PIDTYPE_PGID] = &init_struct_pid, \
+ .pids[PIDTYPE_SID] = &init_struct_pid, \
}

extern struct nsproxy init_nsproxy;
@@ -91,10 +94,10 @@ extern struct group_info init_groups;

#define INIT_STRUCT_PID { \
.count = ATOMIC_INIT(1), \
+ .tsk = &init_task, \
.tasks = { \
- { .first = &init_task.pids[PIDTYPE_PID].node }, \
- { .first = &init_task.pids[PIDTYPE_PGID].node }, \
- { .first = &init_task.pids[PIDTYPE_SID].node }, \
+ { .first = &init_task.pids[PIDTYPE_PGID] }, \
+ { .first = &init_task.pids[PIDTYPE_SID] }, \
}, \
.rcu = RCU_HEAD_INIT, \
.level = 0, \
@@ -105,13 +108,10 @@ extern struct group_info init_groups;
}, } \
}

-#define INIT_PID_LINK(type) \
-{ \
- .node = { \
- .next = NULL, \
- .pprev = &init_struct_pid.tasks[type].first, \
- }, \
- .pid = &init_struct_pid, \
+#define INIT_PID_HLIST_NODE(type) \
+{ \
+ .next = NULL, \
+ .pprev = &init_struct_pid.tasks[type].first, \
}

#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
@@ -179,9 +179,8 @@ extern struct group_info init_groups;
.fs_excl = ATOMIC_INIT(0), \
.pi_lock = __SPIN_LOCK_UNLOCKED(tsk.pi_lock), \
.pids = { \
- [PIDTYPE_PID] = INIT_PID_LINK(PIDTYPE_PID), \
- [PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID), \
- [PIDTYPE_SID] = INIT_PID_LINK(PIDTYPE_SID), \
+ [PIDTYPE_PGID] = INIT_PID_HLIST_NODE(PIDTYPE_PGID), \
+ [PIDTYPE_SID] = INIT_PID_HLIST_NODE(PIDTYPE_SID), \
}, \
.dirties = INIT_PROP_LOCAL_SINGLE(dirties), \
INIT_TRACE_IRQFLAGS \
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 061abb6..828355e 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -5,9 +5,10 @@

enum pid_type
{
- PIDTYPE_PID,
PIDTYPE_PGID,
PIDTYPE_SID,
+ PIDTYPE_PID,
+#define PIDTYPE_ARRAY_MAX PIDTYPE_PID
PIDTYPE_MAX
};

@@ -58,7 +59,8 @@ struct pid
{
atomic_t count;
/* lists of tasks that use this pid */
- struct hlist_head tasks[PIDTYPE_MAX];
+ struct task_struct *tsk;
+ struct hlist_head tasks[PIDTYPE_ARRAY_MAX];
struct rcu_head rcu;
int level;
struct upid numbers[1];
@@ -66,12 +68,6 @@ struct pid

extern struct pid init_struct_pid;

-struct pid_link
-{
- struct hlist_node node;
- struct pid *pid;
-};
-
static inline struct pid *get_pid(struct pid *pid)
{
if (pid)
@@ -158,7 +154,7 @@ static inline pid_t pid_vnr(struct pid *pid)
struct hlist_node *pos___; \
if (pid != NULL) \
hlist_for_each_entry_rcu((task), pos___, \
- &pid->tasks[type], pids[type].node) {
+ &pid->tasks[type], pids[type]) {

#define while_each_pid_task(pid, type, task) \
} \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1b1e25b..496dfda 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -453,7 +453,6 @@ struct signal_struct {

/* ITIMER_REAL timer for the process */
struct hrtimer real_timer;
- struct task_struct *tsk;
ktime_t it_real_incr;

/* ITIMER_PROF and ITIMER_VIRTUAL timers for the process */
@@ -461,6 +460,8 @@ struct signal_struct {
cputime_t it_prof_incr, it_virt_incr;

/* job control IDs */
+ struct pid *tgid;
+ struct pid *pids[PIDTYPE_ARRAY_MAX];

/*
* pgrp and session fields are deprecated.
@@ -1034,8 +1035,9 @@ struct task_struct {
struct list_head sibling; /* linkage in my parent's children list */
struct task_struct *group_leader; /* threadgroup leader */

+ struct pid *tid;
/* PID/PID hash table linkage. */
- struct pid_link pids[PIDTYPE_MAX];
+ struct hlist_node pids[PIDTYPE_ARRAY_MAX];
struct list_head thread_group;

struct completion *vfork_done; /* for vfork() */
@@ -1261,22 +1263,34 @@ static inline void set_task_pgrp(struct task_struct *tsk, pid_t pgrp)

static inline struct pid *task_pid(struct task_struct *task)
{
- return task->pids[PIDTYPE_PID].pid;
+ return task->tid;
}

static inline struct pid *task_tgid(struct task_struct *task)
{
- return task->group_leader->pids[PIDTYPE_PID].pid;
+ struct signal_struct *sig = rcu_dereference(task->signal);
+ struct pid *pid = NULL;
+ if (sig)
+ pid = sig->tgid;
+ return pid;
}

static inline struct pid *task_pgrp(struct task_struct *task)
{
- return task->group_leader->pids[PIDTYPE_PGID].pid;
+ struct signal_struct *sig = rcu_dereference(task->signal);
+ struct pid *pid = NULL;
+ if (sig)
+ pid = sig->pids[PIDTYPE_PGID];
+ return pid;
}

static inline struct pid *task_session(struct task_struct *task)
{
- return task->group_leader->pids[PIDTYPE_SID].pid;
+ struct signal_struct *sig = rcu_dereference(task->signal);
+ struct pid *pid = NULL;
+ if (sig)
+ pid = sig->pids[PIDTYPE_SID];
+ return pid;
}

struct pid_namespace;
@@ -1371,7 +1385,7 @@ static inline pid_t task_ppid_nr_ns(struct task_struct *tsk,
*/
static inline int pid_alive(struct task_struct *p)
{
- return p->pids[PIDTYPE_PID].pid != NULL;
+ return p->signal != NULL;
}

/**
@@ -1652,7 +1666,6 @@ extern void block_all_signals(int (*notifier)(void *priv), void *priv,
extern void unblock_all_signals(void);
extern void release_task(struct task_struct * p);
extern int send_sig_info(int, struct siginfo *, struct task_struct *);
-extern int send_group_sig_info(int, struct siginfo *, struct task_struct *);
extern int force_sigsegv(int, struct task_struct *);
extern int force_sig_info(int, struct siginfo *, struct task_struct *);
extern int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp);
@@ -1772,17 +1785,6 @@ extern void wait_task_inactive(struct task_struct * p);
/* de_thread depends on thread_group_leader not being a pid based check */
#define thread_group_leader(p) (p == p->group_leader)

-/* Do to the insanities of de_thread it is possible for a process
- * to have the pid of the thread group leader without actually being
- * the thread group leader. For iteration through the pids in proc
- * all we care about is that we have a task with the appropriate
- * pid, we don't actually care if we have the right task.
- */
-static inline int has_group_leader_pid(struct task_struct *p)
-{
- return p->pid == p->tgid;
-}
-
static inline
int same_thread_group(struct task_struct *p1, struct task_struct *p2)
{
@@ -1800,9 +1802,6 @@ static inline int thread_group_empty(struct task_struct *p)
return list_empty(&p->thread_group);
}

-#define delay_group_leader(p) \
- (thread_group_leader(p) && !thread_group_empty(p))
-
/*
* Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
* subscriptions and synchronises with wait4(). Also used in procfs. Also
diff --git a/kernel/exit.c b/kernel/exit.c
index 1ab19f0..94552e0 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -57,7 +57,6 @@ static void exit_mm(struct task_struct * tsk);
static void __unhash_process(struct task_struct *p)
{
nr_threads--;
- detach_pid(p, PIDTYPE_PID);
if (thread_group_leader(p)) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
@@ -65,6 +64,7 @@ static void __unhash_process(struct task_struct *p)
list_del_rcu(&p->tasks);
__get_cpu_var(process_counts)--;
}
+ detach_pid(p, PIDTYPE_PID);
list_del_rcu(&p->thread_group);
remove_parent(p);
}
@@ -144,44 +144,15 @@ static void delayed_put_task_struct(struct rcu_head *rhp)

void release_task(struct task_struct * p)
{
- struct task_struct *leader;
- int zap_leader;
-repeat:
atomic_dec(&p->user->processes);
proc_flush_task(p);
write_lock_irq(&tasklist_lock);
ptrace_unlink(p);
BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
__exit_signal(p);
-
- /*
- * If we are the last non-leader member of the thread
- * group, and the leader is zombie, then notify the
- * group leader's parent process. (if it wants notification.)
- */
- zap_leader = 0;
- leader = p->group_leader;
- if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
- BUG_ON(leader->exit_signal == -1);
- do_notify_parent(leader, leader->exit_signal);
- /*
- * If we were the last child thread and the leader has
- * exited already, and the leader's parent ignores SIGCHLD,
- * then we are the one who should release the leader.
- *
- * do_notify_parent() will have marked it self-reaping in
- * that case.
- */
- zap_leader = (leader->exit_signal == -1);
- }
-
write_unlock_irq(&tasklist_lock);
release_thread(p);
call_rcu(&p->rcu, delayed_put_task_struct);
-
- p = leader;
- if (unlikely(zap_leader))
- goto repeat;
}

/*
@@ -633,8 +604,7 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
/* If we'd notified the old parent about this child's death,
* also notify the new parent.
*/
- if (!traced && p->exit_state == EXIT_ZOMBIE &&
- p->exit_signal != -1 && thread_group_empty(p))
+ if (!traced && p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1)
do_notify_parent(p, p->exit_signal);

/*
@@ -702,8 +672,7 @@ static void forget_original_parent(struct task_struct *father)
} else {
/* reparent ptraced task to its real parent */
__ptrace_unlink (p);
- if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
- thread_group_empty(p))
+ if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1)
do_notify_parent(p, p->exit_signal);
}

@@ -773,6 +742,11 @@ static void exit_notify(struct task_struct *tsk)
exit_task_namespaces(tsk);

write_lock_irq(&tasklist_lock);
+ /* If we haven't yet made gettid() == getpid() do so now */
+ if (thread_group_leader(tsk) && (tsk->tid != tsk->signal->tgid)) {
+ detach_pid(tsk, PIDTYPE_PID);
+ attach_pid(tsk, PIDTYPE_PID, tsk->signal->tgid);
+ }
/*
* Check to see if any process groups have become orphaned
* as a result of our exiting, and if they have any stopped
@@ -818,7 +792,7 @@ static void exit_notify(struct task_struct *tsk)
* send it a SIGCHLD instead of honoring exit_signal. exit_signal
* only has special meaning to our real parent.
*/
- if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
+ if (tsk->exit_signal != -1) {
int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
do_notify_parent(tsk, signal);
} else if (tsk->ptrace) {
@@ -946,6 +920,48 @@ fastcall NORET_TYPE void do_exit(long code)
}

tsk->flags |= PF_EXITING;
+ /* Transfer thread group leadership */
+ if (thread_group_leader(tsk) && !thread_group_empty(tsk)) {
+ struct task_struct *new_leader, *t;
+ write_lock_irq(&tasklist_lock);
+ for (t = next_thread(tsk); t != tsk; t = next_thread(t)) {
+ if (!(t->flags & PF_EXITING))
+ break;
+ }
+ if (t != tsk) {
+ new_leader = t;
+
+ new_leader->start_time = tsk->start_time;
+ task_pid(tsk)->tsk = new_leader;
+ transfer_pid(tsk, new_leader, PIDTYPE_PGID);
+ transfer_pid(tsk, new_leader, PIDTYPE_SID);
+ list_replace_rcu(&tsk->tasks, &new_leader->tasks);
+
+ /* Update group_leader on all of the threads... */
+ new_leader->group_leader = new_leader;
+ tsk->group_leader = new_leader;
+ for (t = next_thread(tsk); t != tsk; t= next_thread(t)) {
+ t->group_leader = new_leader;
+ }
+
+ new_leader->exit_signal = tsk->exit_signal;
+ tsk->exit_signal = -1;
+
+ write_unlock_irq(&tasklist_lock);
+ } else {
+ write_unlock_irq(&tasklist_lock);
+ /* Wait for the other threads to exit before continuing */
+ for (;;) {
+ read_lock(&tasklist_lock);
+ if (thread_group_empty(tsk))
+ break;
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ read_unlock(&tasklist_lock);
+ schedule();
+ }
+ read_unlock(&tasklist_lock);
+ }
+ }
/*
* tsk->flags are checked in the futex code to protect against
* an exiting task cleaning up the robust pi futexes.
@@ -1106,20 +1122,18 @@ asmlinkage void sys_exit_group(int error_code)
do_group_exit((error_code & 0xff) << 8);
}

-static int eligible_child(pid_t pid, int options, struct task_struct *p)
+static int eligible_child(enum pid_type type, struct pid *pid, int options, struct task_struct *p)
{
int err;
- struct pid_namespace *ns;

- ns = current->nsproxy->pid_ns;
- if (pid > 0) {
- if (task_pid_nr_ns(p, ns) != pid)
+ if (type == PIDTYPE_PID) {
+ /* Match all pids pointing at task p */
+ if (pid_task(pid, PIDTYPE_PID) != p)
return 0;
- } else if (!pid) {
- if (task_pgrp_nr_ns(p, ns) != task_pgrp_vnr(current))
- return 0;
- } else if (pid != -1) {
- if (task_pgrp_nr_ns(p, ns) != -pid)
+ } else if (type < PIDTYPE_MAX) {
+ struct signal_struct *sig;
+ sig = rcu_dereference(p->signal);
+ if (sig && (sig->pids[type] != pid))
return 0;
}

@@ -1346,7 +1360,8 @@ static int wait_task_stopped(struct task_struct *p,
{
int retval, exit_code, why;
uid_t uid = 0; /* unneeded, required by compiler */
- pid_t pid;
+ struct pid *pid;
+ pid_t upid;

exit_code = 0;
spin_lock_irq(&p->sighand->siglock);
@@ -1382,12 +1397,16 @@ unlock_sig:
* possibly take page faults for user memory.
*/
get_task_struct(p);
- pid = task_pid_nr_ns(p, current->nsproxy->pid_ns);
+ if (p->ptrace && same_thread_group(current, p->parent))
+ pid = task_pid(p);
+ else
+ pid = task_tgid(p);
+ upid = pid_nr_ns(pid, current->nsproxy->pid_ns);
why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
read_unlock(&tasklist_lock);

if (unlikely(noreap))
- return wait_noreap_copyout(p, pid, uid,
+ return wait_noreap_copyout(p, upid, uid,
why, exit_code,
infop, ru);

@@ -1403,11 +1422,11 @@ unlock_sig:
if (!retval && infop)
retval = put_user(exit_code, &infop->si_status);
if (!retval && infop)
- retval = put_user(pid, &infop->si_pid);
+ retval = put_user(upid, &infop->si_pid);
if (!retval && infop)
retval = put_user(uid, &infop->si_uid);
if (!retval)
- retval = pid;
+ retval = upid;
put_task_struct(p);

BUG_ON(!retval);
@@ -1425,7 +1444,8 @@ static int wait_task_continued(struct task_struct *p, int noreap,
int __user *stat_addr, struct rusage __user *ru)
{
int retval;
- pid_t pid;
+ struct pid *pid;
+ pid_t upid;
uid_t uid;

if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
@@ -1440,8 +1460,11 @@ static int wait_task_continued(struct task_struct *p, int noreap,
if (!noreap)
p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
spin_unlock_irq(&p->sighand->siglock);
-
- pid = task_pid_nr_ns(p, current->nsproxy->pid_ns);
+ if (p->ptrace && same_thread_group(current, p->parent))
+ pid = task_pid(p);
+ else
+ pid = task_tgid(p);
+ upid = pid_nr_ns(pid, current->nsproxy->pid_ns);
uid = p->uid;
get_task_struct(p);
read_unlock(&tasklist_lock);
@@ -1452,9 +1475,9 @@ static int wait_task_continued(struct task_struct *p, int noreap,
if (!retval && stat_addr)
retval = put_user(0xffff, stat_addr);
if (!retval)
- retval = pid;
+ retval = upid;
} else {
- retval = wait_noreap_copyout(p, pid, uid,
+ retval = wait_noreap_copyout(p, upid, uid,
CLD_CONTINUED, SIGCONT,
infop, ru);
BUG_ON(retval == 0);
@@ -1463,13 +1486,25 @@ static int wait_task_continued(struct task_struct *p, int noreap,
return retval;
}

-static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
+static long do_wait(pid_t upid, int options, struct siginfo __user *infop,
int __user *stat_addr, struct rusage __user *ru)
{
DECLARE_WAITQUEUE(wait, current);
struct task_struct *tsk;
int flag, retval;
-
+ struct pid *pid = NULL;
+ enum pid_type type = PIDTYPE_MAX;
+
+ if (upid > 0) {
+ type = PIDTYPE_PID;
+ pid = find_get_pid(upid);
+ } else if (upid == 0) {
+ type = PIDTYPE_PGID;
+ pid = get_pid(task_pgrp(current));
+ } else if (upid < -1) {
+ type = PIDTYPE_PGID;
+ pid = find_get_pid(-upid);
+ }
add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
/*
@@ -1484,7 +1519,7 @@ repeat:
struct task_struct *p;

list_for_each_entry(p, &tsk->children, sibling) {
- int ret = eligible_child(pid, options, p);
+ int ret = eligible_child(type, pid, options, p);
if (!ret)
continue;

@@ -1503,8 +1538,7 @@ repeat:
retval = wait_task_stopped(p,
(options & WNOWAIT), infop,
stat_addr, ru);
- } else if (p->exit_state == EXIT_ZOMBIE &&
- !delay_group_leader(p)) {
+ } else if (p->exit_state == EXIT_ZOMBIE) {
/*
* We don't reap group leaders with subthreads.
*/
@@ -1531,7 +1565,7 @@ repeat:
if (!flag) {
list_for_each_entry(p, &tsk->ptrace_children,
ptrace_list) {
- flag = eligible_child(pid, options, p);
+ flag = eligible_child(type, pid, options, p);
if (!flag)
continue;
if (likely(flag > 0))
@@ -1560,6 +1594,7 @@ repeat:
end:
current->state = TASK_RUNNING;
remove_wait_queue(&current->signal->wait_chldexit,&wait);
+ put_pid(pid);
if (infop) {
if (retval > 0)
retval = 0;
diff --git a/kernel/fork.c b/kernel/fork.c
index 7abb592..e986be9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -883,7 +883,6 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
sig->it_real_incr.tv64 = 0;
sig->real_timer.function = it_real_fn;
- sig->tsk = tsk;

sig->it_virt_expires = cputime_zero;
sig->it_virt_incr = cputime_zero;
@@ -1308,6 +1307,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
if (clone_flags & CLONE_NEWPID)
p->nsproxy->pid_ns->child_reaper = p;

+ p->signal->tgid = pid;
p->signal->tty = current->signal->tty;
set_task_pgrp(p, task_pgrp_nr(current));
set_task_session(p, task_session_nr(current));
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 2fab344..f40b589 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -132,7 +132,7 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
struct signal_struct *sig =
container_of(timer, struct signal_struct, real_timer);

- send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
+ kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->tgid);

return HRTIMER_NORESTART;
}
diff --git a/kernel/pid.c b/kernel/pid.c
index 21f027c..b45b53d 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -319,28 +319,39 @@ EXPORT_SYMBOL_GPL(find_pid);
int fastcall attach_pid(struct task_struct *task, enum pid_type type,
struct pid *pid)
{
- struct pid_link *link;
-
- link = &task->pids[type];
- link->pid = pid;
- hlist_add_head_rcu(&link->node, &pid->tasks[type]);
+ if (type == PIDTYPE_PID) {
+ task->tid = pid;
+ pid->tsk = task;
+ }
+ else {
+ task->signal->pids[type] = pid;
+ hlist_add_head_rcu(&task->pids[type], &pid->tasks[type]);
+ }

return 0;
}

void fastcall detach_pid(struct task_struct *task, enum pid_type type)
{
- struct pid_link *link;
- struct pid *pid;
+ struct pid **ppid, *pid;
int tmp;

- link = &task->pids[type];
- pid = link->pid;
-
- hlist_del_rcu(&link->node);
- link->pid = NULL;
+ if (type == PIDTYPE_PID) {
+ ppid = &task->tid;
+ pid = *ppid;
+ if (pid->tsk == task)
+ pid->tsk = NULL;
+ }
+ else {
+ hlist_del_rcu(&task->pids[type]);
+ ppid = &task->signal->pids[type];
+ }
+ pid = *ppid;
+ *ppid = NULL;

- for (tmp = PIDTYPE_MAX; --tmp >= 0; )
+ if (pid->tsk)
+ return;
+ for (tmp = PIDTYPE_MAX -1; --tmp >= 0; )
if (!hlist_empty(&pid->tasks[tmp]))
return;

@@ -351,19 +362,22 @@ void fastcall detach_pid(struct task_struct *task, enum pid_type type)
void fastcall transfer_pid(struct task_struct *old, struct task_struct *new,
enum pid_type type)
{
- new->pids[type].pid = old->pids[type].pid;
- hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node);
- old->pids[type].pid = NULL;
+ hlist_replace_rcu(&old->pids[type], &new->pids[type]);
}

struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type)
{
struct task_struct *result = NULL;
if (pid) {
- struct hlist_node *first;
- first = rcu_dereference(pid->tasks[type].first);
- if (first)
- result = hlist_entry(first, struct task_struct, pids[(type)].node);
+ if (type == PIDTYPE_PID)
+ result = rcu_dereference(pid->tsk);
+ else {
+ struct hlist_node *first;
+ first = rcu_dereference(pid->tasks[type].first);
+ if (first)
+ result = hlist_entry(first, struct task_struct,
+ pids[(type)]);
+ }
}
return result;
}
@@ -402,7 +416,11 @@ struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
{
struct pid *pid;
rcu_read_lock();
- pid = get_pid(task->pids[type].pid);
+ if (type == PIDTYPE_PID)
+ pid = task->tid;
+ else
+ pid = task->signal->pids[type];
+ get_pid(pid);
rcu_read_unlock();
return pid;
}
diff --git a/kernel/signal.c b/kernel/signal.c
index 06e663d..af8c49f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1195,20 +1195,6 @@ send_sig(int sig, struct task_struct *p, int priv)
return send_sig_info(sig, __si_special(priv), p);
}

-/*
- * This is the entry point for "process-wide" signals.
- * They will go to an appropriate thread in the thread group.
- */
-int
-send_group_sig_info(int sig, struct siginfo *info, struct task_struct *p)
-{
- int ret;
- read_lock(&tasklist_lock);
- ret = group_send_sig_info(sig, info, p);
- read_unlock(&tasklist_lock);
- return ret;
-}
-
void
force_sig(int sig, struct task_struct *p)
{
@@ -1501,12 +1487,15 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
unsigned long flags;
struct task_struct *parent;
struct sighand_struct *sighand;
+ struct pid *pid;

- if (tsk->ptrace & PT_PTRACED)
+ if (tsk->ptrace & PT_PTRACED) {
parent = tsk->parent;
- else {
+ pid = task_pid(tsk);
+ } else {
tsk = tsk->group_leader;
parent = tsk->real_parent;
+ pid = task_tgid(tsk);
}

info.si_signo = SIGCHLD;
@@ -1515,7 +1504,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
* see comment in do_notify_parent() abot the following 3 lines
*/
rcu_read_lock();
- info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
+ info.si_pid = pid_nr_ns(pid, parent->nsproxy->pid_ns);
rcu_read_unlock();

info.si_uid = tsk->uid;
--
1.5.3.rc6.17.g1911

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