From: Sergey Vlasov <vsu@altlinux.ru>
To: linux-hotplug@vger.kernel.org
Subject: Re: Udev - Trapping "Add" - Subsystem "module"
Date: Thu, 09 Nov 2006 20:58:37 +0000 [thread overview]
Message-ID: <20061109235837.f0b9fedd.vsu@altlinux.ru> (raw)
In-Reply-To: <335DD0B75189FB428E5C32680089FB9F8040B0@mtk-sms-mail01.digi.com>
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On Thu, 9 Nov 2006 12:44:52 -0600 Kilau, Scott wrote:
> My rule (currently I put in "10-dgap.rules"):
>
> ACTION=="add", KERNEL=="dgap", SUBSYSTEM=="module", \
> RUN+="/usr/sbin/dgapdl", OPTIONS+="last_rule"
This does not seem to be a good idea. The module add event is
generated early - even before the module init routine is invoked; so
the program you run may even find that the module was not loaded
because the module initialization failed. And even if the module
loads successfully, there will be a race - when your program will try
to access your module, it might break because the module init is not
yet complete. This race might be hard to notice on an uniprocessor
machine, because the udevd process which handles uevents will most
likely be scheduled only after the module init code completes (but you
should be able to reproduce it easily if you insert some sleeps in the
module init code).
The proper way to handle initialization is to have your module
register some devices and then catch addition of these devices in udev
rules. At this time you can be sure that the corresponding device
file has been created by udevd.
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next prev parent reply other threads:[~2006-11-09 20:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-09 18:44 Udev - Trapping "Add" - Subsystem "module" Kilau, Scott
2006-11-09 19:09 ` Kris van Rens
2006-11-09 19:17 ` Kilau, Scott
2006-11-09 19:22 ` Kris van Rens
2006-11-09 20:58 ` Sergey Vlasov [this message]
2006-11-10 2:05 ` Kilau, Scott
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