Move prepare to wait around, so that normal GFP_KERNEL allocation can
be used.
Signed-off-by: Pavel Machek (CIP) <[email protected]>
Acked-by: Alan Stern <[email protected]>
diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index b2e09883c7e2..071f1debebba 100644
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -489,10 +489,10 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
}
/* send the data as the control msg */
- prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
dev->cntl_buffer[0]);
- retval = usb_submit_urb(dev->cntl_urb, GFP_ATOMIC);
+ retval = usb_submit_urb(dev->cntl_urb, GFP_KERNEL);
+ prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
if (retval >= 0)
timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
finish_wait(&dev->waitq, &wait);
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Am Sonntag, den 20.09.2020, 10:44 +0200 schrieb Pavel Machek:
> Move prepare to wait around, so that normal GFP_KERNEL allocation can
> be used.
>
> Signed-off-by: Pavel Machek (CIP) <[email protected]>
> Acked-by: Alan Stern <[email protected]>
Ehm. Please recheck.
> diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
> index b2e09883c7e2..071f1debebba 100644
> --- a/drivers/usb/misc/yurex.c
> +++ b/drivers/usb/misc/yurex.c
> @@ -489,10 +489,10 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
> }
>
> /* send the data as the control msg */
> - prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
> dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
> dev->cntl_buffer[0]);
> - retval = usb_submit_urb(dev->cntl_urb, GFP_ATOMIC);
> + retval = usb_submit_urb(dev->cntl_urb, GFP_KERNEL);
URB completes here. wake_up() returns the task to RUNNING.
> + prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
Task goes to TASK_INTERRUPTIBLE
> if (retval >= 0)
> timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
Task turns into Sleeping Beauty until timeout
> finish_wait(&dev->waitq, &wait);
And here task goes into error reporting as it checks timeout.
Regards
Oliver
Hi!
> > Move prepare to wait around, so that normal GFP_KERNEL allocation can
> > be used.
> >
> > Signed-off-by: Pavel Machek (CIP) <[email protected]>
> > Acked-by: Alan Stern <[email protected]>
>
> Ehm. Please recheck.
Sorry about that.
> > +++ b/drivers/usb/misc/yurex.c
> > @@ -489,10 +489,10 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
> > }
> >
> > /* send the data as the control msg */
> > - prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
> > dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
> > dev->cntl_buffer[0]);
> > - retval = usb_submit_urb(dev->cntl_urb, GFP_ATOMIC);
> > + retval = usb_submit_urb(dev->cntl_urb, GFP_KERNEL);
>
> URB completes here. wake_up() returns the task to RUNNING.
>
> > + prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
>
> Task goes to TASK_INTERRUPTIBLE
>
> > if (retval >= 0)
> > timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
>
> Task turns into Sleeping Beauty until timeout
Is there way to do the allocations for submit_urb before the
prepare_to_wait? GFP_ATOMIC would be nice to avoid... and doing
GFP_ATOMIC from normal process context just because of task_state
seems ... wrong.
Pavel
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Am Montag, den 21.09.2020, 14:52 +0200 schrieb Pavel Machek:
> Hi!
> >
> > Task goes to TASK_INTERRUPTIBLE
> >
> > > if (retval >= 0)
> > > timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
> >
> > Task turns into Sleeping Beauty until timeout
>
> Is there way to do the allocations for submit_urb before the
No. In theory you do not even know which HC will get the URB.
Preallocating resources is impossible. I do consider this a
design bug in the usbcore API.
> prepare_to_wait? GFP_ATOMIC would be nice to avoid... and doing
> GFP_ATOMIC from normal process context just because of task_state
> seems ... wrong.
Well, then you will need to change the rest of the logic
and use a struct completion. Give the age and practical
relevance of the driver I would recommend against making
such drastic changes and let it just be in its awkward
but correct state.
Regards
Oliver
On Mon, Sep 21, 2020 at 02:24:52PM +0200, Oliver Neukum wrote:
> Am Sonntag, den 20.09.2020, 10:44 +0200 schrieb Pavel Machek:
> > Move prepare to wait around, so that normal GFP_KERNEL allocation can
> > be used.
> >
> > Signed-off-by: Pavel Machek (CIP) <[email protected]>
> > Acked-by: Alan Stern <[email protected]>
>
> Ehm. Please recheck.
>
> > diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
> > index b2e09883c7e2..071f1debebba 100644
> > --- a/drivers/usb/misc/yurex.c
> > +++ b/drivers/usb/misc/yurex.c
> > @@ -489,10 +489,10 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
> > }
> >
> > /* send the data as the control msg */
> > - prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
> > dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
> > dev->cntl_buffer[0]);
> > - retval = usb_submit_urb(dev->cntl_urb, GFP_ATOMIC);
> > + retval = usb_submit_urb(dev->cntl_urb, GFP_KERNEL);
>
> URB completes here. wake_up() returns the task to RUNNING.
>
> > + prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
>
> Task goes to TASK_INTERRUPTIBLE
>
> > if (retval >= 0)
> > timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
>
> Task turns into Sleeping Beauty until timeout
>
> > finish_wait(&dev->waitq, &wait);
>
> And here task goes into error reporting as it checks timeout.
Arrgh. Now I feel stupid. (Me and Pavel both, probably.)
Thanks for spotting this.
Alan Stern