| Message ID | 20200920084452.GA2257@amd (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | usb: yurex: Rearrange code not to need GFP_ATOMIC | expand |
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) <pavel@denx.de> > Acked-by: Alan Stern <stern@rowland.harvard.edu> 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) <pavel@denx.de> > > Acked-by: Alan Stern <stern@rowland.harvard.edu> > > 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
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) <pavel@denx.de> > > Acked-by: Alan Stern <stern@rowland.harvard.edu> > > 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
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);