[Bug 7034] New: modprobe misunderstands some modaliases and fails to load

bugzilla at busybox.net bugzilla at busybox.net
Thu Apr 17 18:52:36 UTC 2014


https://bugs.busybox.net/show_bug.cgi?id=7034

           Summary: modprobe misunderstands some modaliases and fails to
                    load
           Product: Busybox
           Version: 1.21.x
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: major
          Priority: P5
         Component: Other
        AssignedTo: unassigned at busybox.net
        ReportedBy: BitJam at gmail.com
                CC: busybox-cvs at busybox.net
   Estimated Hours: 0.0


When using mdev hotplugging or automatic hardware detection, modprobe must load
modules by modalias instead of just by module name.  Most of the time this
works but there are occasional failures that lead (in my case) to systems not
booting.

For example, with the normal Linux modprobe, the following command will load
the pata_via module:

modprobe pci:v00001106d00000571sv00001509sd00009022bc01sc01i8a

but the busybox modprobe does nothing.  The vast majority of modules do get
loaded correctly so this is not a generic problem with a missing
modules.dep.bb.

grep pata_via modules.dep.bb | sed 's/ /\n/g':

live/pata_via.ko
pci:v00001106d00009001sv*sd*bc*sc*i*
pci:v00001106d0000C409sv*sd*bc*sc*i*
pci:v00001106d00005324sv*sd*bc*sc*i*
pci:v00001106d00003164sv*sd*bc*sc*i*
pci:v00001106d00001571sv*sd*bc*sc*i*
pci:v00001106d00000581sv*sd*bc*sc*i*
pci:v00001106d00000571sv*sd*bc*sc*i*
pci:v00001106d00000415sv*sd*bc*sc*i*

The entry that should have matched but did not is:
pci:v00001106d00000571sv*sd*bc*sc*i*

This is the same modalias information used by working versions of modprobe.

The reason I gave this report a high priority is because it's a show-stopper
bug for using busybox in generic live systems with automatic hardware detection
but it only fails on some systems.  Intermittent failures are often worse than
total failures.  Most of the time it works as expected so the bug is not
replicated on any of my test systems and may in general be hard to catch during
testing.  Also, the cause of the problem was not clear.  I had assumed modprobe
was working and I was not calling it correctly.

My work-around is to use a standalone kmod program.  Since I already need to
use libc, the addition of kmod and its lib only adds about 80K (compressed).

I hope the information here will make it easy to track down and fix the bug.  I
don't have time to delve into your code now.   I have other examples of
failures with other modules but this is the only example I have with complete
modalias information.

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