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Commit 4d1d61a6 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Al Viro
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Gordeev <agordeev@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Smith <dsmith@redhat.com>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent e73f8959

include/linux/interrupt.h

+0 −4
Original line number Diff line number Diff line
@@ -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 *);

include/linux/sched.h

+2 −8
Original line number Diff line number Diff line
@@ -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;
@@ -1313,7 +1308,6 @@ 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

kernel/exit.c

+0 −2
Original line number Diff line number Diff line
@@ -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),

kernel/irq/manage.c

+33 −35
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/interrupt.h>

#include <linux/slab.h>

#include <linux/sched.h>

#include <linux/task_work.h>



#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, &param);

	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)