Commit 0dfc6246 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Thomas Gleixner
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[MTD] NAND: Reorganize chip locking 



The code was wrong in several aspects. The locking order was
inconsistent, the device aquire code did not reset a variable
after a wakeup and the wakeup handling was not working for
applications where multiple chips are sharing a single
hardware controller.
When a hardware controller is available the locking is now
reduced to the hardware controller lock and the waitqueue is
moved to the hardware controller structure in order to avoid
a wake_up_all().

The problem was pointed out by Ben Dooks, who also found the
missing variable reset as main cause for his deadlock problem.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7ca6448d

drivers/mtd/nand/nand_base.c

+29 −28
Original line number Diff line number Diff line
@@ -59,7 +59,7 @@ 
 *	The AG-AND chips have nice features for speed improvement,

 *	which are not supported yet. Read / program 4 pages in one go.

 *

 * $Id: nand_base.c,v 1.143 2005/05/19 16:10:22 gleixner Exp $

 * $Id: nand_base.c,v 1.145 2005/05/31 20:32:53 gleixner Exp $

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as
@@ -167,18 +167,22 @@ static void nand_release_device (struct mtd_info *mtd) 


	/* De-select the NAND device */

	this->select_chip(mtd, -1);

	/* Do we have a hardware controller ? */



	if (this->controller) {

		/* Release the controller and the chip */

		spin_lock(&this->controller->lock);

		this->controller->active = NULL;

		this->state = FL_READY;

		wake_up(&this->controller->wq);

		spin_unlock(&this->controller->lock);

	}

	} else {

		/* Release the chip */

		spin_lock(&this->chip_lock);

		this->state = FL_READY;

		wake_up(&this->wq);

		spin_unlock(&this->chip_lock);

	}

}



/**

 * nand_read_byte - [DEFAULT] read one byte from the chip
@@ -753,37 +757,34 @@ static void nand_command_lp (struct mtd_info *mtd, unsigned command, int column, 
 */

static void nand_get_device (struct nand_chip *this, struct mtd_info *mtd, int new_state)

{

	struct nand_chip *active = this;



	struct nand_chip *active;

	spinlock_t *lock;

	wait_queue_head_t *wq;

	DECLARE_WAITQUEUE (wait, current);



	/* 

	 * Grab the lock and see if the device is available 

	*/

	lock = (this->controller) ? &this->controller->lock : &this->chip_lock;

	wq = (this->controller) ? &this->controller->wq : &this->wq;

retry:

	active = this;

	spin_lock(lock);



	/* Hardware controller shared among independend devices */

	if (this->controller) {

		spin_lock (&this->controller->lock);

		if (this->controller->active)

			active = this->controller->active;

		else

			this->controller->active = this;

		spin_unlock (&this->controller->lock);

	}

	

	if (active == this) {

		spin_lock (&this->chip_lock);

		if (this->state == FL_READY) {

	if (active == this && this->state == FL_READY) {

		this->state = new_state;

			spin_unlock (&this->chip_lock);

		spin_unlock(lock);

		return;

	}

	}	

	set_current_state(TASK_UNINTERRUPTIBLE);

	add_wait_queue (&active->wq, &wait);

	spin_unlock (&active->chip_lock);

	add_wait_queue(wq, &wait);

	spin_unlock(lock);

	schedule();

	remove_wait_queue (&active->wq, &wait);

	remove_wait_queue(wq, &wait);

	goto retry;

}

include/linux/mtd/nand.h

+4 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
 *                     Steven J. Hill <sjhill@realitydiluted.com>

 *		       Thomas Gleixner <tglx@linutronix.de>

 *

 * $Id: nand.h,v 1.71 2005/02/09 12:12:59 gleixner Exp $

 * $Id: nand.h,v 1.73 2005/05/31 19:39:17 gleixner Exp $

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as
@@ -253,10 +253,13 @@ struct nand_chip; 
 * struct nand_hw_control - Control structure for hardware controller (e.g ECC generator) shared among independend devices

 * @lock:               protection lock  

 * @active:		the mtd device which holds the controller currently

 * @wq:			wait queue to sleep on if a NAND operation is in progress

 *                      used instead of the per chip wait queue when a hw controller is available

 */

struct nand_hw_control {

	spinlock_t	 lock;

	struct nand_chip *active;

	wait_queue_head_t wq;

};



/**

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