Messages in this thread | | | From | Yoshihiro Shimoda <> | Subject | RE: [RFC][PATCH v2 2/2] driver core: Ensure wait_for_device_probe() waits until the deferred_probe_timeout fires | Date | Wed, 8 Apr 2020 10:29:20 +0000 |
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Hi John,
> From: John Stultz, Sent: Wednesday, April 8, 2020 4:27 PM > > In commit c8c43cee29f6 ("driver core: Fix > driver_deferred_probe_check_state() logic"), we set the default > driver_deferred_probe_timeout value to 30 seconds to allow for > drivers that are missing dependencies to have some time so that > the dependency may be loaded from userland after initcalls_done > is set. > > However, Yoshihiro Shimoda reported that on his device that > expects to have unmet dependencies (due to "optional links" in > its devicetree), was failing to mount the NFS root. > > In digging further, it seemed the problem was that while the > device properly probes after waiting 30 seconds for any missing > modules to load, the ip_auto_config() had already failed, > resulting in NFS to fail. This was due to ip_auto_config() > calling wait_for_device_probe() which doesn't wait for the > driver_deferred_probe_timeout to fire. > > This patch tries to fix the issue by creating a waitqueue > for the driver_deferred_probe_timeout, and calling wait_event() > to make sure driver_deferred_probe_timeout is zero in > wait_for_device_probe() to make sure all the probing is > finished. > > The downside to this solution is that kernel functionality that > uses wait_for_device_probe(), will block until the > driver_deferred_probe_timeout fires, regardless of if there is > any missing dependencies. > > However, the previous patch reverts the default timeout value to > zero, so this side-effect will only affect users who specify a > driver_deferred_probe_timeout= value as a boot argument, where > the additional delay would be beneficial to allow modules to > load later during boot. > > Thanks to Geert for chasing down that ip_auto_config was why NFS > was failing in this case! > > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> > Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Rafael J. Wysocki <rjw@rjwysocki.net> > Cc: Rob Herring <robh@kernel.org> > Cc: Geert Uytterhoeven <geert@linux-m68k.org> > Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> > Cc: netdev <netdev@vger.kernel.org> > Cc: linux-pm@vger.kernel.org > Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> > Fixes: c8c43cee29f6 ("driver core: Fix driver_deferred_probe_check_state() logic") > Signed-off-by: John Stultz <john.stultz@linaro.org> > --- > * v2: Split patch, and apply it as a follow-on to setting > the driver_deferred_probe_timeout defalt back to zero > ---
Thank you for the patch! This patch doesn't cause any side effect on my environment (the value of driver_deferred_probe_timeout is 0). So,
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Best regards, Yoshihiro Shimoda
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