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Date: Wed, 20 Aug 2008 20:13:57 +0400
From: Oleg Nesterov <oleg@...sign.ru>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Roland McGrath <roland@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] posix-timers: use "struct pid*" instead of "struct task_struct*"
k_itimer holds the ref to the ->it_process until sys_timer_delete(). This
allows to pin up to RLIMIT_SIGPENDING dead task_struct's. Change the code
to use "struct pid *" instead.
The patch doesn't kill ->it_process, it places ->it_pid into the union.
->it_process is still used by do_cpu_nanosleep() as before. It would be
trivial to change the nanosleep code as well, but since it uses it_process
in a special way I think it is better to keep this field for grep.
The patch bloats the kernel by 104 bytes and it also adds the new pointer,
->it_signal, to k_itimer. It is used by lock_timer() to verify that the
found timer was not created by another process. It is not clear why do we
use the global database (and thus the global idr_lock) for posix timers.
We still need the signal_struct->posix_timers which contains all useable
timers, perhaps it is better to use some form of per-process array instead.
Signed-off-by: Oleg Nesterov <oleg@...sign.ru>
include/linux/posix-timers.h | 6 +++++-
kernel/posix-timers.c | 43 +++++++++++++++++++++++--------------------
2 files changed, 28 insertions(+), 21 deletions(-)
--- 26-rc2/include/linux/posix-timers.h~11_S_TASK_PID 2008-08-05 16:11:11.000000000 +0400
+++ 26-rc2/include/linux/posix-timers.h 2008-08-17 17:26:52.000000000 +0400
@@ -45,7 +45,11 @@ struct k_itimer {
int it_requeue_pending; /* waiting to requeue this timer */
#define REQUEUE_PENDING 1
int it_sigev_notify; /* notify word of sigevent struct */
- struct task_struct *it_process; /* process to send signal to */
+ struct signal_struct *it_signal;
+ union {
+ struct pid *it_pid; /* pid of process to send signal to */
+ struct task_struct *it_process; /* for clock_nanosleep */
+ };
struct sigqueue *sigq; /* signal queue entry. */
union {
struct {
--- 26-rc2/kernel/posix-timers.c~11_S_TASK_PID 2008-08-05 18:53:19.000000000 +0400
+++ 26-rc2/kernel/posix-timers.c 2008-08-17 18:34:09.000000000 +0400
@@ -116,7 +116,7 @@ static DEFINE_SPINLOCK(idr_lock);
* must supply functions here, even if the function just returns
* ENOSYS. The standard POSIX timer management code assumes the
* following: 1.) The k_itimer struct (sched.h) is used for the
- * timer. 2.) The list, it_lock, it_clock, it_id and it_process
+ * timer. 2.) The list, it_lock, it_clock, it_id and it_pid
* fields are not modified by timer code.
*
* At this time all functions EXCEPT clock_nanosleep can be
@@ -298,7 +298,8 @@ void do_schedule_next_timer(struct sigin
int posix_timer_event(struct k_itimer *timr, int si_private)
{
- int shared, ret;
+ struct task_struct *task;
+ int shared, ret = -1;
/*
* FIXME: if ->sigq is queued we can race with
* dequeue_signal()->do_schedule_next_timer().
@@ -312,8 +313,13 @@ int posix_timer_event(struct k_itimer *t
*/
timr->sigq->info.si_sys_private = si_private;
- shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
- ret = send_sigqueue(timr->sigq, timr->it_process, shared);
+ rcu_read_lock();
+ task = pid_task(timr->it_pid, PIDTYPE_PID);
+ if (task) {
+ shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
+ ret = send_sigqueue(timr->sigq, task, shared);
+ }
+ rcu_read_unlock();
/* If we failed to send the signal the timer stops. */
return ret > 0;
}
@@ -390,7 +396,7 @@ static enum hrtimer_restart posix_timer_
return ret;
}
-static struct task_struct * good_sigevent(sigevent_t * event)
+static struct pid *good_sigevent(sigevent_t * event)
{
struct task_struct *rtn = current->group_leader;
@@ -404,7 +410,7 @@ static struct task_struct * good_sigeven
((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))
return NULL;
- return rtn;
+ return task_pid(rtn);
}
void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
@@ -457,9 +463,9 @@ sys_timer_create(const clockid_t which_c
int error;
struct k_itimer *new_timer;
int new_timer_id;
- struct task_struct *process;
sigevent_t event;
int it_id_set = IT_ID_NOT_SET;
+ struct pid *it_pid;
if (invalid_clockid(which_clock))
return -EINVAL;
@@ -511,11 +517,9 @@ sys_timer_create(const clockid_t which_c
goto out;
}
rcu_read_lock();
- process = good_sigevent(&event);
- if (process)
- get_task_struct(process);
+ it_pid = get_pid(good_sigevent(&event));
rcu_read_unlock();
- if (!process) {
+ if (!it_pid) {
error = -EINVAL;
goto out;
}
@@ -523,8 +527,7 @@ sys_timer_create(const clockid_t which_c
event.sigev_notify = SIGEV_SIGNAL;
event.sigev_signo = SIGALRM;
event.sigev_value.sival_int = new_timer->it_id;
- process = current->group_leader;
- get_task_struct(process);
+ it_pid = get_pid(task_tgid(current));
}
new_timer->it_sigev_notify = event.sigev_notify;
@@ -534,7 +537,8 @@ sys_timer_create(const clockid_t which_c
new_timer->sigq->info.si_code = SI_TIMER;
spin_lock_irq(¤t->sighand->siglock);
- new_timer->it_process = process;
+ new_timer->it_pid = it_pid;
+ new_timer->it_signal = current->signal;
list_add(&new_timer->list, ¤t->signal->posix_timers);
spin_unlock_irq(¤t->sighand->siglock);
@@ -569,8 +573,7 @@ static struct k_itimer *lock_timer(timer
timr = idr_find(&posix_timers_id, (int)timer_id);
if (timr) {
spin_lock(&timr->it_lock);
- if (timr->it_process &&
- same_thread_group(timr->it_process, current)) {
+ if (timr->it_pid && timr->it_signal == current->signal) {
spin_unlock(&idr_lock);
return timr;
}
@@ -819,8 +822,8 @@ retry_delete:
* This keeps any tasks waiting on the spin lock from thinking
* they got something (see the lock code above).
*/
- put_task_struct(timer->it_process);
- timer->it_process = NULL;
+ put_pid(timer->it_pid);
+ timer->it_pid = NULL;
unlock_timer(timer, flags);
release_posix_timer(timer, IT_ID_SET);
@@ -846,8 +849,8 @@ retry_delete:
* This keeps any tasks waiting on the spin lock from thinking
* they got something (see the lock code above).
*/
- put_task_struct(timer->it_process);
- timer->it_process = NULL;
+ put_pid(timer->it_pid);
+ timer->it_pid = NULL;
unlock_timer(timer, flags);
release_posix_timer(timer, IT_ID_SET);
--
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