2007-05-05 22:17:13

by Oleg Nesterov

Subject: [PATCH -mm] libata-core: convert to use cancel_rearming_delayed_work()

Compile tested, depends on

make-cancel_rearming_delayed_work-reliable.patch

We should not use cancel_work_sync(delayed_work->work). This works, but not
good. We can use cancel_rearming_delayed_work(), this also simplifies the
code.

Signed-off-by: Oleg Nesterov <[email protected]>

drivers/ata/libata-core.c | 44 ++++----------------------------------------
include/linux/libata.h | 1 -
2 files changed, 4 insertions(+), 41 deletions(-)

--- OLD/include/linux/libata.h~ATA 2007-04-05 12:20:35.000000000 +0400
+++ OLD/include/linux/libata.h 2007-05-06 01:41:10.000000000 +0400
@@ -192,7 +192,6 @@ enum {
ATA_PFLAG_UNLOADING = (1 << 5), /* module is unloading */
ATA_PFLAG_SCSI_HOTPLUG = (1 << 6), /* SCSI hotplug scheduled */

- ATA_PFLAG_FLUSH_PORT_TASK = (1 << 16), /* flush port task */
ATA_PFLAG_SUSPENDED = (1 << 17), /* port is suspended (power) */
ATA_PFLAG_PM_PENDING = (1 << 18), /* PM operation pending */

--- OLD/drivers/ata/libata-core.c~ATA 2007-04-05 12:20:34.000000000 +0400
+++ OLD/drivers/ata/libata-core.c 2007-05-06 01:53:43.000000000 +0400
@@ -1079,18 +1079,11 @@ static unsigned int ata_id_xfermask(cons
void ata_port_queue_task(struct ata_port *ap, work_func_t fn, void *data,
unsigned long delay)
{
- int rc;
-
- if (ap->pflags & ATA_PFLAG_FLUSH_PORT_TASK)
- return;
-
PREPARE_DELAYED_WORK(&ap->port_task, fn);
ap->port_task_data = data;

- rc = queue_delayed_work(ata_wq, &ap->port_task, delay);
-
- /* rc == 0 means that another user is using port task */
- WARN_ON(rc == 0);
+ /* may fail if ata_port_flush_task() in progress */
+ queue_delayed_work(ata_wq, &ap->port_task, delay);
}

/**
@@ -1105,32 +1098,9 @@ void ata_port_queue_task(struct ata_port
*/
void ata_port_flush_task(struct ata_port *ap)
{
- unsigned long flags;
-
DPRINTK("ENTER\n");

- spin_lock_irqsave(ap->lock, flags);
- ap->pflags |= ATA_PFLAG_FLUSH_PORT_TASK;
- spin_unlock_irqrestore(ap->lock, flags);
-
- DPRINTK("flush #1\n");
- cancel_work_sync(&ap->port_task.work); /* akpm: seems unneeded */
-
- /*
- * At this point, if a task is running, it's guaranteed to see
- * the FLUSH flag; thus, it will never queue pio tasks again.
- * Cancel and flush.
- */
- if (!cancel_delayed_work(&ap->port_task)) {
- if (ata_msg_ctl(ap))
- ata_port_printk(ap, KERN_DEBUG, "%s: flush #2\n",
- __FUNCTION__);
- cancel_work_sync(&ap->port_task.work);
- }
-
- spin_lock_irqsave(ap->lock, flags);
- ap->pflags &= ~ATA_PFLAG_FLUSH_PORT_TASK;
- spin_unlock_irqrestore(ap->lock, flags);
+ cancel_rearming_delayed_work(&ap->port_task);

if (ata_msg_ctl(ap))
ata_port_printk(ap, KERN_DEBUG, "%s: EXIT\n", __FUNCTION__);
@@ -6094,13 +6064,7 @@ void ata_port_detach(struct ata_port *ap
spin_unlock_irqrestore(ap->lock, flags);

ata_port_wait_eh(ap);
-
- /* Flush hotplug task. The sequence is similar to
- * ata_port_flush_task().
- */
- cancel_work_sync(&ap->hotplug_task.work); /* akpm: why? */
- cancel_delayed_work(&ap->hotplug_task);
- cancel_work_sync(&ap->hotplug_task.work);
+ cancel_rearming_delayed_work(&ap->hotplug_task);

skip_eh:
/* remove the associated SCSI host */

2007-05-11 14:19:08

by Tejun Heo

Subject: Re: [PATCH -mm] libata-core: convert to use cancel_rearming_delayed_work()

Hello,

Oleg Nesterov wrote:
> void ata_port_queue_task(struct ata_port *ap, work_func_t fn, void *data,
> unsigned long delay)
> {
> - int rc;
> -
> - if (ap->pflags & ATA_PFLAG_FLUSH_PORT_TASK)
> - return;
> -
> PREPARE_DELAYED_WORK(&ap->port_task, fn);
> ap->port_task_data = data;
>
> - rc = queue_delayed_work(ata_wq, &ap->port_task, delay);
> -
> - /* rc == 0 means that another user is using port task */
> - WARN_ON(rc == 0);
> + /* may fail if ata_port_flush_task() in progress */
> + queue_delayed_work(ata_wq, &ap->port_task, delay);
> }

I don't really think ata_port_queue_task() deserves to live after this.
Feel free to kill it.

> void ata_port_flush_task(struct ata_port *ap)
> {
> - unsigned long flags;
> -
> DPRINTK("ENTER\n");
>
> - spin_lock_irqsave(ap->lock, flags);
> - ap->pflags |= ATA_PFLAG_FLUSH_PORT_TASK;
> - spin_unlock_irqrestore(ap->lock, flags);
> -
> - DPRINTK("flush #1\n");
> - cancel_work_sync(&ap->port_task.work); /* akpm: seems unneeded */
> -
> - /*
> - * At this point, if a task is running, it's guaranteed to see
> - * the FLUSH flag; thus, it will never queue pio tasks again.
> - * Cancel and flush.
> - */
> - if (!cancel_delayed_work(&ap->port_task)) {
> - if (ata_msg_ctl(ap))
> - ata_port_printk(ap, KERN_DEBUG, "%s: flush #2\n",
> - __FUNCTION__);
> - cancel_work_sync(&ap->port_task.work);
> - }
> -
> - spin_lock_irqsave(ap->lock, flags);
> - ap->pflags &= ~ATA_PFLAG_FLUSH_PORT_TASK;
> - spin_unlock_irqrestore(ap->lock, flags);
> + cancel_rearming_delayed_work(&ap->port_task);

Nor does ata_port_flush_task().

> @@ -6094,13 +6064,7 @@ void ata_port_detach(struct ata_port *ap
> spin_unlock_irqrestore(ap->lock, flags);
>
> ata_port_wait_eh(ap);
> -
> - /* Flush hotplug task. The sequence is similar to
> - * ata_port_flush_task().
> - */
> - cancel_work_sync(&ap->hotplug_task.work); /* akpm: why? */
> - cancel_delayed_work(&ap->hotplug_task);
> - cancel_work_sync(&ap->hotplug_task.work);
> + cancel_rearming_delayed_work(&ap->hotplug_task);

Yay, I've always wanted to do that. :-)

Thanks.

--
tejun