The patch titled posix-timers: sys_timer_create: simplify and s/tasklist/rcu/ has been removed from the -mm tree. Its filename was posix-timers-sys_timer_create-simplify-and-s-tasklist-rcu.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: posix-timers: sys_timer_create: simplify and s/tasklist/rcu/ From: Oleg Nesterov <oleg@xxxxxxxxxx> - 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@xxxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/posix-timers.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff -puN kernel/posix-timers.c~posix-timers-sys_timer_create-simplify-and-s-tasklist-rcu kernel/posix-timers.c --- a/kernel/posix-timers.c~posix-timers-sys_timer_create-simplify-and-s-tasklist-rcu +++ a/kernel/posix-timers.c @@ -478,7 +478,6 @@ 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; @@ -536,16 +535,11 @@ 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; @@ -556,19 +550,18 @@ 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); _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are git-tip.patch posix-timers-use-struct-pid-instead-of-struct-task_struct.patch posix-timers-check-it_signal-instead-of-it_pid-to-validate-the-timer.patch posix-timers-simplify-de_thread-exit_itimers-path.patch signal-procfs-lock_task_sighand-do-not-need-rcu_read_lock.patch make-ptrace_untrace-static.patch coredump-format_corename-dont-append-%pid-if-multi-threaded.patch add-config_core_dump_default_elf_headers.patch kthread_bind-use-wait_task_inactivetask_uninterruptible.patch pid_ns-de_thread-kill-the-now-unneeded-child_reaper-change.patch pid_ns-kill-the-now-unused-task_child_reaper.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html