[lm-sensors] sensors-detect: probing i2c sensors racy?

Forest Bond forest at alittletooquiet.net
Wed Dec 9 17:23:01 CET 2009


Thanks for the quick reply.

On Wed, Dec 09, 2009 at 05:11:48PM +0100, Jean Delvare wrote:
> On Wed, 9 Dec 2009 10:32:25 -0500, Forest Bond wrote:
> > I am seeing a situation where sensors-detect fails to find sensors in a single
> > run due to an apparent race condition.  It looks like it loads the i2c-* modules
> > and then tries to open /dev/i2c-0 for probing, but it fails to open
> > successfully.  My sense is that the device is not fully initialize and ready for
> > opening immediately following the modprobe calls, but sensors-detect does not
> > wait for initialization to complete.  I'm not sure what should be happening.  It
> > seems sensible that modprobe would not return until the device is initialized.
> > 
> > Running sensors-detect again correctly probes the hardware because the i2c bus
> > is fully initialized at that point.
> You must be typing very fast to be able to trigger this ;) Or udev is
> very slow populating /dev on your machine.

You got me ;).

I'm doing this:

  yes '' | sensors-detect 2>&1 | tee sensors-detect.log

> > I don't know anything about i2c, so I hope the language I'm using to describe
> > this situation is reasonable.
> It is perfect.
> > I've attached the output from sensors-detect for the first (failed) run and the
> > second (successful) run.
> > 
> > Thoughts?
> The version of the sensors-detect you're using is getting old. Please
> give a try to the latest one:
> http://dl.lm-sensors.org/lm-sensors/files/sensors-detect
> If you can still reproduce the problem, then please give a try to the
> attached patch and report.

Okay, I'll give this a try.

Forest Bond
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