Re: [PATCH] modules: Only return -EEXIST for modules that have finished loading

[Jessica Yu]

+++ Prarit Bhargava [15/04/19 08:04 -0400]:
> On 4/15/19 7:23 AM, Jessica Yu wrote:
> > +++ Prarit Bhargava [02/04/19 09:39 -0400]:
> > > Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
> > > linux guests boot with repeated errors:
> > >
> > > amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
> > > amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
> > > amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
> > > amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
> > > amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
> > > amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
> > >
> > > The warnings occur because the module code erroneously returns -EEXIST
> > > for modules that have failed to load and are in the process of being
> > > removed from the module list.
> > >
> > > module amd64_edac_mod has a dependency on module edac_mce_amd.  Using
> > > modules.dep, systemd will load edac_mce_amd for every request of
> > > amd64_edac_mod.  When the edac_mce_amd module loads, the module has
> > > state MODULE_STATE_UNFORMED and once the module load fails and the state
> > > becomes MODULE_STATE_GOING.  Another request for edac_mce_amd module
> > > executes and add_unformed_module() will erroneously return -EEXIST even
> > > though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
> > > Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
> > > fails because of unknown symbols from edac_mce_amd.
> > >
> > > add_unformed_module() must wait to return for any case other than
> > > MODULE_STATE_LIVE to prevent a race between multiple loads of
> > > dependent modules.
> > >
> > > Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
> > > Reported-by: Cathy Avery <cavery@xxxxxxxxxx>
> > > Cc: Jessica Yu <jeyu@xxxxxxxxxx>
> >
> > Applied to modules-next. Thanks Prarit!
>
> Jessica, could I have the URL of the git tree?

Sure, you can find the modules-next branch at:

   git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux.git

Thanks,

Jessica