[sane-devel] scanimage hangs at shutdown (Preparing for a sane-backends release)

[Rolf Bensch]

Hi Olaf,

Good idea, but it doesn't work. Many thanks for your help.

Cheers,
Rolf

Am 19.08.2015 um 03:27 schrieb Olaf Meeuwissen:
> 
> Rolf Bensch writes:
> 
>> Using fork or pthread makes no difference.
>>
>> A sleep at the end of main() works wonders.
>>
>> But not for the other exit() functions. 'scanimage -h' or 'scanimage -A'
>> still hang with the same issue.
>>
>> I suggest to replace atexit and all exit() functions by the existing
>> scanimage_exit() function.
>>
>> Please check if attached patch is running with your installations.
> 
> I had a look at the patch and tripped over the fixme.  Next, I had a
> look at the scanimage_exit() implementation and the timing of adding
> that to the list of functions to call atexit.  Something definitely
> smells there.
> 
>  - scanimage_exit() may call sane_close().  That function may need to do
>    device I/O.
>  - scanimage_exit() is register with atexit() *before* sane_init() gets
>    called.  This means that any functions registered via atexit() in a
>    backend run *before* scanimage_exit().
>  - none of the backends call atexit() directly but any library they use
>    may register exit handlers
> 
> Is there any chance that the libusb-compat installations that are
> affected register an exit handler?  Say something like libusb_exit()?
> If that is the case, device I/O will be made impossible *before*
> scanimage_exit() gets a chance to sane_close() the device.
> 
> Note that the -h and -A options to scanimage need the device's options
> so that just about guarantees that its backend needs to talk to it.
> 
> Does moving the atexit() call *after* sane_init() fix this issue?
> 
> Hope this helps,
>