Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 7 Apr 2020 18:46:02 +0200 | Subject | Re: [RFC][PATCH] driver core: Ensure wait_for_device_probe() waits until the deferred_probe_timeout fires |
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Hi John,
On Tue, Apr 7, 2020 at 9:50 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > On Tue, Apr 7, 2020 at 9:06 AM John Stultz <john.stultz@linaro.org> wrote: > > 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. > > > > NOTE: I'm not 100% sure this won't have other unwanted side > > effects (I don't have failing hardware myself to validate), > > so I'd apprecate testing and close review. > > > > If this approach doesn't work, I'll simply set the default > > driver_deferred_probe_timeout value back to zero, to avoid any > > behavioral change from before. > > > > 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> > > Thanks, this fixes the issue for me! > > Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Unfortunately this adds another delay of ca. 30 s to mounting NFS root when using a kernel config that does include IOMMU and MODULES support.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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