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Commit 656d9125 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[S390] 3215 deadlock with tty_wakeup 



The 3215 driver calls tty_wakeup from irq context while holding the
device spinlock. If printk is called by any function on the callchain
starting from tty_wakeup the system deadlocks on the device spinlock.
Using a tasklet to call tty_wakup solves the problem.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 2320c579

drivers/s390/char/con3215.c

+15 −7
Original line number Original line Diff line number Diff line
@@ -87,6 +87,7 @@ struct raw3215_info { 
	struct tty_struct *tty;	      /* pointer to tty structure if present */

	struct tty_struct *tty;	      /* pointer to tty structure if present */

	struct raw3215_req *queued_read; /* pointer to queued read requests */

	struct raw3215_req *queued_read; /* pointer to queued read requests */

	struct raw3215_req *queued_write;/* pointer to queued write requests */

	struct raw3215_req *queued_write;/* pointer to queued write requests */

	struct tasklet_struct tlet;   /* tasklet to invoke tty_wakeup */

	wait_queue_head_t empty_wait; /* wait queue for flushing */

	wait_queue_head_t empty_wait; /* wait queue for flushing */

	struct timer_list timer;      /* timer for delayed output */

	struct timer_list timer;      /* timer for delayed output */

	int line_pos;		      /* position on the line (for tabs) */

	int line_pos;		      /* position on the line (for tabs) */
@@ -333,20 +334,24 @@ static inline void raw3215_try_io(struct raw3215_info *raw) 
	}

	}

}

}





/*

 * Call tty_wakeup from tasklet context

 */

static void raw3215_wakeup(unsigned long data)

{

	struct raw3215_info *raw = (struct raw3215_info *) data;

	tty_wakeup(raw->tty);

}



/*

/*

 * Try to start the next IO and wake up processes waiting on the tty.

 * Try to start the next IO and wake up processes waiting on the tty.

 */

 */

static void raw3215_next_io(struct raw3215_info *raw)

static void raw3215_next_io(struct raw3215_info *raw)

{

{

	struct tty_struct *tty;



	raw3215_mk_write_req(raw);

	raw3215_mk_write_req(raw);

	raw3215_try_io(raw);

	raw3215_try_io(raw);

	tty = raw->tty;

	if (raw->tty && RAW3215_BUFFER_SIZE - raw->count >= RAW3215_MIN_SPACE)

	if (tty != NULL &&

		tasklet_schedule(&raw->tlet);

	    RAW3215_BUFFER_SIZE - raw->count >= RAW3215_MIN_SPACE) {

	    	tty_wakeup(tty);

	}

}

}





/*

/*
@@ -682,6 +687,7 @@ static int raw3215_probe (struct ccw_device *cdev) 
		return -ENOMEM;

		return -ENOMEM;

	}

	}

	init_waitqueue_head(&raw->empty_wait);

	init_waitqueue_head(&raw->empty_wait);

	tasklet_init(&raw->tlet, raw3215_wakeup, (unsigned long) raw);





	dev_set_drvdata(&cdev->dev, raw);

	dev_set_drvdata(&cdev->dev, raw);

	cdev->handler = raw3215_irq;

	cdev->handler = raw3215_irq;
@@ -901,6 +907,7 @@ static int __init con3215_init(void) 




	raw->flags |= RAW3215_FIXED;

	raw->flags |= RAW3215_FIXED;

	init_waitqueue_head(&raw->empty_wait);

	init_waitqueue_head(&raw->empty_wait);

	tasklet_init(&raw->tlet, raw3215_wakeup, (unsigned long) raw);





	/* Request the console irq */

	/* Request the console irq */

	if (raw3215_startup(raw) != 0) {

	if (raw3215_startup(raw) != 0) {
@@ -966,6 +973,7 @@ static void tty3215_close(struct tty_struct *tty, struct file * filp) 
	tty->closing = 1;

	tty->closing = 1;

	/* Shutdown the terminal */

	/* Shutdown the terminal */

	raw3215_shutdown(raw);

	raw3215_shutdown(raw);

	tasklet_kill(&raw->tlet);

	tty->closing = 0;

	tty->closing = 0;

	raw->tty = NULL;

	raw->tty = NULL;

}

}