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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: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2005-05-31 20:39:20 +01:00 committed by Thomas Gleixner
parent 7ca6448dbf
commit 0dfc62465e
2 changed files with 33 additions and 29 deletions
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57
drivers/mtd/nand/nand_base.c
View File

@ -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
@ -167,17 +167,21 @@ 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);
}
/* Release the chip */
spin_lock (&this->chip_lock);
this->state = FL_READY;
wake_up (&this->wq);
spin_unlock (&this->chip_lock);
}
/**
@ -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) {
this->state = new_state;
spin_unlock (&this->chip_lock);
return;
}
}
set_current_state (TASK_UNINTERRUPTIBLE);
add_wait_queue (&active->wq, &wait);
spin_unlock (&active->chip_lock);
schedule ();
remove_wait_queue (&active->wq, &wait);
if (active == this && this->state == FL_READY) {
this->state = new_state;
spin_unlock(lock);
return;
}
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(wq, &wait);
spin_unlock(lock);
schedule();
remove_wait_queue(wq, &wait);
goto retry;
}

5
include/linux/mtd/nand.h
View File

@ -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;
};
/**