Commit 5b31f855 authored by Bartlomiej Zolnierkiewicz's avatar Bartlomiej Zolnierkiewicz
Browse files

ide: use lock bitops for ports serialization (v2) 



* Add ->host_busy field to struct ide_host and use it's first bit
  together with lock bitops to provide new ports serialization method.

* Convert core IDE code to use new ide_[un]lock_host() helpers.

  This removes the need for taking hwgroup->lock if host is already
  busy on serialized hosts and makes it possible to merge ide_hwgroup_t
  into ide_hwif_t (done in the later patch).

* Remove no longer needed ide_hwgroup_t.busy and ide_[un]lock_hwgroup().

* Update do_ide_request() documentation.

v2:
* ide_release_lock() should be called inside IDE_HFLAG_SERIALIZE check.

* Add ide_hwif_t.busy flag and ide_[un]lock_port() for serializing
  devices on a port.

Signed-off-by: default avatarBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
parent efe0397e

drivers/ide/ide-io.c

+63 −42
Original line number Diff line number Diff line
@@ -666,45 +666,54 @@ void ide_stall_queue (ide_drive_t *drive, unsigned long timeout) 
}

EXPORT_SYMBOL(ide_stall_queue);



static inline int ide_lock_port(ide_hwif_t *hwif)

{

	if (hwif->busy)

		return 1;



	hwif->busy = 1;



	return 0;

}



static inline void ide_unlock_port(ide_hwif_t *hwif)

{

	hwif->busy = 0;

}



static inline int ide_lock_host(struct ide_host *host, ide_hwif_t *hwif)

{

	int rc = 0;



	if (host->host_flags & IDE_HFLAG_SERIALIZE) {

		rc = test_and_set_bit_lock(IDE_HOST_BUSY, &host->host_busy);

		if (rc == 0) {

			/* for atari only */

			ide_get_lock(ide_intr, hwif);

		}

	}

	return rc;

}



static inline void ide_unlock_host(struct ide_host *host)

{

	if (host->host_flags & IDE_HFLAG_SERIALIZE) {

		/* for atari only */

		ide_release_lock();

		clear_bit_unlock(IDE_HOST_BUSY, &host->host_busy);

	}

}



/*

 * Issue a new request to a drive from hwgroup

 *

 * A hwgroup is a serialized group of IDE interfaces.  Usually there is

 * exactly one hwif (interface) per hwgroup, but buggy controllers (eg. CMD640)

 * may have both interfaces in a single hwgroup to "serialize" access.

 * Or possibly multiple ISA interfaces can share a common IRQ by being grouped

 * together into one hwgroup for serialized access.

 *

 * Note also that several hwgroups can end up sharing a single IRQ,

 * possibly along with many other devices.  This is especially common in

 * PCI-based systems with off-board IDE controller cards.

 *

 * The IDE driver uses a per-hwgroup lock to protect the hwgroup->busy flag.

 *

 * The first thread into the driver for a particular hwgroup sets the

 * hwgroup->busy flag to indicate that this hwgroup is now active,

 * and then initiates processing of the top request from the request queue.

 *

 * Other threads attempting entry notice the busy setting, and will simply

 * queue their new requests and exit immediately.  Note that hwgroup->busy

 * remains set even when the driver is merely awaiting the next interrupt.

 * Thus, the meaning is "this hwgroup is busy processing a request".

 *

 * When processing of a request completes, the completing thread or IRQ-handler

 * will start the next request from the queue.  If no more work remains,

 * the driver will clear the hwgroup->busy flag and exit.

 *

 * The per-hwgroup spinlock is used to protect all access to the

 * hwgroup->busy flag, but is otherwise not needed for most processing in

 * the driver.  This makes the driver much more friendlier to shared IRQs

 * than previous designs, while remaining 100% (?) SMP safe and capable.

 */

void do_ide_request(struct request_queue *q)

{

	ide_drive_t	*drive = q->queuedata;

	ide_hwif_t	*hwif = drive->hwif;

	struct ide_host *host = hwif->host;

	ide_hwgroup_t	*hwgroup = hwif->hwgroup;

	struct request	*rq;

	struct request	*rq = NULL;

	ide_startstop_t	startstop;



	/*
@@ -721,9 +730,13 @@ void do_ide_request(struct request_queue *q) 
		blk_remove_plug(q);



	spin_unlock_irq(q->queue_lock);



	if (ide_lock_host(host, hwif))

		goto plug_device_2;



	spin_lock_irq(&hwgroup->lock);



	if (!ide_lock_hwgroup(hwgroup, hwif)) {

	if (!ide_lock_port(hwif)) {

		ide_hwif_t *prev_port;

repeat:

		prev_port = hwif->host->cur_port;
@@ -731,7 +744,7 @@ repeat: 


		if (drive->dev_flags & IDE_DFLAG_SLEEPING) {

			if (time_before(drive->sleep, jiffies)) {

				ide_unlock_hwgroup(hwgroup);

				ide_unlock_port(hwif);

				goto plug_device;

			}

		}
@@ -761,7 +774,7 @@ repeat: 
		spin_lock_irq(&hwgroup->lock);



		if (!rq) {

			ide_unlock_hwgroup(hwgroup);

			ide_unlock_port(hwif);

			goto out;

		}
@@ -782,7 +795,7 @@ repeat: 
		    blk_pm_request(rq) == 0 &&

		    (rq->cmd_flags & REQ_PREEMPT) == 0) {

			/* there should be no pending command at this point */

			ide_unlock_hwgroup(hwgroup);

			ide_unlock_port(hwif);

			goto plug_device;

		}
@@ -798,11 +811,15 @@ repeat: 
		goto plug_device;

out:

	spin_unlock_irq(&hwgroup->lock);

	if (rq == NULL)

		ide_unlock_host(host);

	spin_lock_irq(q->queue_lock);

	return;



plug_device:

	spin_unlock_irq(&hwgroup->lock);

	ide_unlock_host(host);

plug_device_2:

	spin_lock_irq(q->queue_lock);



	if (!elv_queue_empty(q))
@@ -844,9 +861,9 @@ static ide_startstop_t ide_dma_timeout_retry(ide_drive_t *drive, int error) 
	ide_dma_off_quietly(drive);



	/*

	 * un-busy drive etc (hwgroup->busy is cleared on return) and

	 * make sure request is sane

	 * un-busy drive etc and make sure request is sane

	 */



	rq = HWGROUP(drive)->rq;



	if (!rq)
@@ -895,6 +912,7 @@ static void ide_plug_device(ide_drive_t *drive) 
void ide_timer_expiry (unsigned long data)

{

	ide_hwgroup_t	*hwgroup = (ide_hwgroup_t *) data;

	ide_hwif_t	*uninitialized_var(hwif);

	ide_drive_t	*uninitialized_var(drive);

	ide_handler_t	*handler;

	ide_expiry_t	*expiry;
@@ -918,7 +936,6 @@ void ide_timer_expiry (unsigned long data) 
			printk(KERN_ERR "%s: ->cur_dev was NULL\n", __func__);

			hwgroup->handler = NULL;

		} else {

			ide_hwif_t *hwif;

			ide_startstop_t startstop = ide_stopped;



			if ((expiry = hwgroup->expiry) != NULL) {
@@ -964,16 +981,18 @@ void ide_timer_expiry (unsigned long data) 
			spin_lock_irq(&hwgroup->lock);

			enable_irq(hwif->irq);

			if (startstop == ide_stopped) {

				ide_unlock_hwgroup(hwgroup);

				ide_unlock_port(hwif);

				plug_device = 1;

			}

		}

	}

	spin_unlock_irqrestore(&hwgroup->lock, flags);



	if (plug_device)

	if (plug_device) {

		ide_unlock_host(hwif->host);

		ide_plug_device(drive);

	}

}



/**

 *	unexpected_intr		-	handle an unexpected IDE interrupt
@@ -1150,7 +1169,7 @@ irqreturn_t ide_intr (int irq, void *dev_id) 
	 */

	if (startstop == ide_stopped) {

		if (hwgroup->handler == NULL) {	/* paranoia */

			ide_unlock_hwgroup(hwgroup);

			ide_unlock_port(hwif);

			plug_device = 1;

		} else

			printk(KERN_ERR "%s: %s: huh? expected NULL handler "
@@ -1161,8 +1180,10 @@ out_handled: 
out:

	spin_unlock_irqrestore(&hwgroup->lock, flags);

out_early:

	if (plug_device)

	if (plug_device) {

		ide_unlock_host(hwif->host);

		ide_plug_device(drive);

	}



	return irq_ret;

}

include/linux/ide.h

+6 −29
Original line number Diff line number Diff line
@@ -828,6 +828,7 @@ typedef struct hwif_s { 


	unsigned	present    : 1;	/* this interface exists */

	unsigned	sg_mapped  : 1;	/* sg_table and sg_nents are ready */

	unsigned	busy	   : 1; /* serializes devices on a port */



	struct device		gendev;

	struct device		*portdev;
@@ -851,8 +852,13 @@ struct ide_host { 
	unsigned long	host_flags;

	void		*host_priv;

	ide_hwif_t	*cur_port;	/* for hosts requiring serialization */



	/* used for hosts requiring serialization */

	volatile long	host_busy;

};



#define IDE_HOST_BUSY 0



/*

 *  internal ide interrupt handler type

 */
@@ -866,8 +872,6 @@ typedef struct hwgroup_s { 
		/* irq handler, if active */

	ide_startstop_t	(*handler)(ide_drive_t *);



		/* BOOL: protects all fields below */

	volatile int busy;

		/* BOOL: polling active & poll_timeout field valid */

	unsigned int polling	: 1;
@@ -1271,26 +1275,6 @@ extern void ide_stall_queue(ide_drive_t *drive, unsigned long timeout); 


extern void ide_timer_expiry(unsigned long);

extern irqreturn_t ide_intr(int irq, void *dev_id);



static inline int ide_lock_hwgroup(ide_hwgroup_t *hwgroup, ide_hwif_t *hwif)

{

	if (hwgroup->busy)

		return 1;



	hwgroup->busy = 1;

	/* for atari only */

	ide_get_lock(ide_intr, hwif);



	return 0;

}



static inline void ide_unlock_hwgroup(ide_hwgroup_t *hwgroup)

{

	/* for atari only */

	ide_release_lock();

	hwgroup->busy = 0;

}



extern void do_ide_request(struct request_queue *);



void ide_init_disk(struct gendisk *, ide_drive_t *);
@@ -1617,13 +1601,6 @@ static inline void ide_set_max_pio(ide_drive_t *drive) 


extern spinlock_t ide_lock;

extern struct mutex ide_cfg_mtx;

/*

 * Structure locking:

 *

 * ide_hwgroup_t->busy: hwgroup->lock

 * ide_hwif_t->{hwgroup,mate}: constant, no locking

 * ide_drive_t->hwif: constant, no locking

 */



#define local_irq_set(flags)	do { local_save_flags((flags)); local_irq_enable_in_hardirq(); } while (0)

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