Messages in this thread Patch in this message | | | Date | Mon, 4 Aug 2008 20:01:04 +0400 | From | Oleg Nesterov <> | Subject | [PATCH 2/4] posix-timers: sys_timer_create: simplify and s/tasklist/rcu/ |
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- Change the code to do rcu_read_lock() instead of taking tasklist_lock, it is safe to get_task_struct(p) if p was found under RCU.
However, now we must not use process's sighand/signal, they may be NULL. We can use current->sighand/signal instead, this "process" must belong to the current's thread-group.
- Factor out the common code for 2 "if (timer_event_spec)" branches, the !timer_event_spec case can use current too.
- use spin_lock_irq() instead of _irqsave(), kill "flags".
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
--- 26-rc2/kernel/posix-timers.c~5_CLEANUP 2008-08-04 16:50:29.000000000 +0400 +++ 26-rc2/kernel/posix-timers.c 2008-08-04 18:13:10.000000000 +0400 @@ -463,7 +463,6 @@ sys_timer_create(const clockid_t which_c struct k_itimer *new_timer; int new_timer_id; struct task_struct *process; - unsigned long flags; sigevent_t event; int it_id_set = IT_ID_NOT_SET; @@ -521,16 +520,11 @@ sys_timer_create(const clockid_t which_c new_timer->it_sigev_signo = event.sigev_signo; new_timer->it_sigev_value = event.sigev_value; - read_lock(&tasklist_lock); - if ((process = good_sigevent(&event))) { + rcu_read_lock(); + process = good_sigevent(&event); + if (process) get_task_struct(process); - spin_lock_irqsave(&process->sighand->siglock, flags); - new_timer->it_process = process; - list_add(&new_timer->list, - &process->signal->posix_timers); - spin_unlock_irqrestore(&process->sighand->siglock, flags); - } - read_unlock(&tasklist_lock); + rcu_read_unlock(); if (!process) { error = -EINVAL; goto out; @@ -541,19 +535,18 @@ sys_timer_create(const clockid_t which_c new_timer->it_sigev_value.sival_int = new_timer->it_id; process = current->group_leader; get_task_struct(process); - spin_lock_irqsave(&process->sighand->siglock, flags); - new_timer->it_process = process; - list_add(&new_timer->list, &process->signal->posix_timers); - spin_unlock_irqrestore(&process->sighand->siglock, flags); } + spin_lock_irq(¤t->sighand->siglock); + new_timer->it_process = process; + list_add(&new_timer->list, ¤t->signal->posix_timers); + spin_unlock_irq(¤t->sighand->siglock); /* * In the case of the timer belonging to another task, after * the task is unlocked, the timer is owned by the other task * and may cease to exist at any time. Don't use or modify * new_timer after the unlock call. */ - out: if (error) release_posix_timer(new_timer, it_id_set);
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