Re: [PATCH v2] firmware: fix sending -ERESTARTSYS due to signal on fallback

["Luis R. Rodriguez" <mcgrof@kernel.org>]

Using the right linux-fsdevel this time also, this was the second reply.

  Luis

On Tue, Jun 06, 2017 at 06:47:34PM +0200, Luis R. Rodriguez wrote:
> Adding fsdevel folks.
> 
> On Tue, Jun 06, 2017 at 03:53:16PM +0100, Alan Cox wrote:
> > > "Unix tradition (and thus almost all applications) believe file store
> > > writes to
> > > be non signal interruptible. It would not be safe or practical to
> > > change that
> > > guarantee."
> > 
> > Yep everyone codes
> > 
> > 	write(disk_file, "foo", 3);
> > 
> > not while(..) blah around it.
> 
> Thanks for the confirmation! That's a simple enough explanation.
> 
> > > For these two reasons then it would seem best we do two things
> > > actually:
> > > 
> > > 1) return -EINTR instead of -EAGAIN when we detect
> > > swait_event_interruptible_timeout()
> > > got interrupted by a signal (it returns -ERESTARTSYS)
> > > 2) Do as you note below and add wait_event_killable_timeout()
> > 
> > Pedantic detail that I don't think affects you
> > 
> > If you have completed a part of the I/O then you should return the byte
> > processed count not EINTR, but -1,EINTR if no progress was made.
> 
> You are right with some new exceptions and with regards to the future:
> 
> The syfs loading interface for firmware currently goes through the
> data file exposed on syfs, the respective write op firmware_data_write()
> only checks for signals at the beginning. After that its a full one
> swoop try to write if you are following the old tradition and are using
> a buffer allocated by the firmware API.
> 
> If you are using the relatively new request_firmware_into_buf() added
> by Stephen Boyd which lets the driver provide the allocated buffer then
> we have a loop in firmware_rw() which should be fixed to:
> 
> 1) Check for signals
> 2) Do what you noted above.
> 
> Furthermore Yi Li over at Intel is adding some new API calls which would
> re-use some of this for FPGA firmwares which are also very large, that
> work should consider the above and fix appropriately as well.
> 
>   Luis
> 

-- 
Luis Rodriguez, SUSE LINUX GmbH
Maxfeldstrasse 5; D-90409 Nuernberg