From e73f8959af0439d114847eab5a8a5ce48f1217c4 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 11 May 2012 10:59:07 +1000 Subject: task_work_add: generic process-context callbacks Provide a simple mechanism that allows running code in the (nonatomic) context of the arbitrary task. The caller does task_work_add(task, task_work) and this task executes task_work->func() either from do_notify_resume() or from do_exit(). The callback can rely on PF_EXITING to detect the latter case. "struct task_work" can be embedded in another struct, still it has "void *data" to handle the most common/simple case. This allows us to kill the ->replacement_session_keyring hack, and potentially this can have more users. Performance-wise, this adds 2 "unlikely(!hlist_empty())" checks into tracehook_notify_resume() and do_exit(). But at the same time we can remove the "replacement_session_keyring != NULL" checks from arch/*/signal.c and exit_creds(). Note: task_work_add/task_work_run abuses ->pi_lock. This is only because this lock is already used by lookup_pi_state() to synchronize with do_exit() setting PF_EXITING. Fortunately the scope of this lock in task_work.c is really tiny, and the code is unlikely anyway. Signed-off-by: Oleg Nesterov Acked-by: David Howells Cc: Thomas Gleixner Cc: Richard Kuo Cc: Linus Torvalds Cc: Alexander Gordeev Cc: Chris Zankel Cc: David Smith Cc: "Frank Ch. Eigler" Cc: Geert Uytterhoeven Cc: Larry Woodman Cc: Peter Zijlstra Cc: Tejun Heo Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- kernel/exit.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'kernel/exit.c') diff --git a/kernel/exit.c b/kernel/exit.c index 910a0716e17a..3d93325e0b1a 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -946,11 +946,14 @@ void do_exit(long code) exit_signals(tsk); /* sets PF_EXITING */ /* * tsk->flags are checked in the futex code to protect against - * an exiting task cleaning up the robust pi futexes. + * an exiting task cleaning up the robust pi futexes, and in + * task_work_add() to avoid the race with exit_task_work(). */ smp_mb(); raw_spin_unlock_wait(&tsk->pi_lock); + exit_task_work(tsk); + exit_irq_thread(); if (unlikely(in_atomic())) -- cgit v1.2.3 From 4d1d61a6b203d957777d73fcebf19d90b038b5b2 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 11 May 2012 10:59:08 +1000 Subject: genirq: reimplement exit_irq_thread() hook via task_work_add() exit_irq_thread() and task->irq_thread are needed to handle the unexpected (and unlikely) exit of irq-thread. We can use task_work instead and make this all private to kernel/irq/manage.c, cleanup plus micro-optimization. 1. rename exit_irq_thread() to irq_thread_dtor(), make it static, and move it up before irq_thread(). 2. change irq_thread() to do task_work_add(irq_thread_dtor) at the start and task_work_cancel() before return. tracehook_notify_resume() can never play with kthreads, only do_exit()->exit_task_work() can call the callback and this is what we want. 3. remove task_struct->irq_thread and the special hook in do_exit(). Signed-off-by: Oleg Nesterov Reviewed-by: Thomas Gleixner Cc: David Howells Cc: Richard Kuo Cc: Linus Torvalds Cc: Alexander Gordeev Cc: Chris Zankel Cc: David Smith Cc: "Frank Ch. Eigler" Cc: Geert Uytterhoeven Cc: Larry Woodman Cc: Peter Zijlstra Cc: Tejun Heo Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- include/linux/interrupt.h | 4 --- include/linux/sched.h | 10 ++----- kernel/exit.c | 2 -- kernel/irq/manage.c | 68 +++++++++++++++++++++++------------------------ 4 files changed, 35 insertions(+), 49 deletions(-) (limited to 'kernel/exit.c') diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index c91171599cb6..e68a8e53bb59 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -142,8 +142,6 @@ request_any_context_irq(unsigned int irq, irq_handler_t handler, extern int __must_check request_percpu_irq(unsigned int irq, irq_handler_t handler, const char *devname, void __percpu *percpu_dev_id); - -extern void exit_irq_thread(void); #else extern int __must_check @@ -177,8 +175,6 @@ request_percpu_irq(unsigned int irq, irq_handler_t handler, { return request_irq(irq, handler, 0, devname, percpu_dev_id); } - -static inline void exit_irq_thread(void) { } #endif extern void free_irq(unsigned int, void *); diff --git a/include/linux/sched.h b/include/linux/sched.h index 7930131abc1a..da013853a622 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1301,11 +1301,6 @@ struct task_struct { unsigned sched_reset_on_fork:1; unsigned sched_contributes_to_load:1; -#ifdef CONFIG_GENERIC_HARDIRQS - /* IRQ handler threads */ - unsigned irq_thread:1; -#endif - pid_t pid; pid_t tgid; @@ -1313,10 +1308,9 @@ struct task_struct { /* Canary value for the -fstack-protector gcc feature */ unsigned long stack_canary; #endif - - /* + /* * pointers to (original) parent process, youngest child, younger sibling, - * older sibling, respectively. (p->father can be replaced with + * older sibling, respectively. (p->father can be replaced with * p->real_parent->pid) */ struct task_struct __rcu *real_parent; /* real parent process */ diff --git a/kernel/exit.c b/kernel/exit.c index 3d93325e0b1a..3ecd096e5d4d 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -954,8 +954,6 @@ void do_exit(long code) exit_task_work(tsk); - exit_irq_thread(); - if (unlikely(in_atomic())) printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n", current->comm, task_pid_nr(current), diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index bb32326afe87..4d1f8f897414 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -14,6 +14,7 @@ #include #include #include +#include #include "internals.h" @@ -773,11 +774,39 @@ static void wake_threads_waitq(struct irq_desc *desc) wake_up(&desc->wait_for_threads); } +static void irq_thread_dtor(struct task_work *unused) +{ + struct task_struct *tsk = current; + struct irq_desc *desc; + struct irqaction *action; + + if (WARN_ON_ONCE(!(current->flags & PF_EXITING))) + return; + + action = kthread_data(tsk); + + pr_err("genirq: exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n", + tsk->comm ? tsk->comm : "", tsk->pid, action->irq); + + + desc = irq_to_desc(action->irq); + /* + * If IRQTF_RUNTHREAD is set, we need to decrement + * desc->threads_active and wake possible waiters. + */ + if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags)) + wake_threads_waitq(desc); + + /* Prevent a stale desc->threads_oneshot */ + irq_finalize_oneshot(desc, action); +} + /* * Interrupt handler thread */ static int irq_thread(void *data) { + struct task_work on_exit_work; static const struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO/2, }; @@ -793,7 +822,9 @@ static int irq_thread(void *data) handler_fn = irq_thread_fn; sched_setscheduler(current, SCHED_FIFO, ¶m); - current->irq_thread = 1; + + init_task_work(&on_exit_work, irq_thread_dtor, NULL); + task_work_add(current, &on_exit_work, false); while (!irq_wait_for_interrupt(action)) { irqreturn_t action_ret; @@ -815,44 +846,11 @@ static int irq_thread(void *data) * cannot touch the oneshot mask at this point anymore as * __setup_irq() might have given out currents thread_mask * again. - * - * Clear irq_thread. Otherwise exit_irq_thread() would make - * fuzz about an active irq thread going into nirvana. */ - current->irq_thread = 0; + task_work_cancel(current, irq_thread_dtor); return 0; } -/* - * Called from do_exit() - */ -void exit_irq_thread(void) -{ - struct task_struct *tsk = current; - struct irq_desc *desc; - struct irqaction *action; - - if (!tsk->irq_thread) - return; - - action = kthread_data(tsk); - - pr_err("genirq: exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n", - tsk->comm ? tsk->comm : "", tsk->pid, action->irq); - - desc = irq_to_desc(action->irq); - - /* - * If IRQTF_RUNTHREAD is set, we need to decrement - * desc->threads_active and wake possible waiters. - */ - if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags)) - wake_threads_waitq(desc); - - /* Prevent a stale desc->threads_oneshot */ - irq_finalize_oneshot(desc, action); -} - static void irq_setup_forced_threading(struct irqaction *new) { if (!force_irqthreads) -- cgit v1.2.3