[sane-devel] Fwd: Re: scanbd occasionally ignores scanner button presses

Wilhelm wilhelm.meier at fh-kl.de
Fri May 16 12:19:14 UTC 2014

Hi Milan,

Am 16.05.2014 09:38, schrieb Milan Knížek:
> Hello devs!
> I have setup scanbd to poll CanoScan 9000F button presses (Arch Linux,
> x86_64, sane-git from 2013-07-08, scanbd 1.3.1), scanbd.service and
> scanbm.socket are run through systemd unit files.
> It usually works just fine, but randomly scanbd completely ignores the
> button presses - usually, it does not even help to switch the scanner
> off/on. The only reliable solution so far is to restart the
> scanbd.service.
> I increased the debug level to 3 and watched syslog for messages when
> scanbd operates normally and when it ignores the presses. I could not
> find anything unusual in the messages. Scanbd continues to send lot of
> repeated messages (like in normal state), but pressing a button does not
> log any messages anymore.
> I have yet to confirm it by further testing, but it seems that I can
> trigger the "stale" status of the scanbd by repeatedly pressing the
> scanner button (e.g. the PDF merge button, which does not really scan
> anything) in a quick sequence.
> Is this a known behaviour? How can I debug it further?

not as far as I know.

> Is there any SIGNAL I could send to scanbd process to refresh itself
> without the need to restart scanbd.service?

Try to send SIGUSR1 to stop all polling and then SIGUSR2 to restart all

> At the moment, I implemented a workaround by killing (SIGKILL) the
> scanbd process every time the button is pressed and restarting
> scanbd.service (at the end of the action script).
> regards,
> Milan

w.meier at unix.net

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