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Date: Fri, 3 Jun 2022 20:54:31 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Stephen Rothwell <sfr@...b.auug.org.au>,
Saravana Kannan <saravanak@...gle.com>,
John Stultz <jstultz@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Jakub Kicinski <kuba@...nel.org>,
"Rafael J . Wysocki" <rjw@...ysocki.net>,
Rob Herring <robh@...nel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
Robin Murphy <robin.murphy@....com>,
Andy Shevchenko <andy.shevchenko@...il.com>,
Sudeep Holla <sudeep.holla@....com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Naresh Kamboju <naresh.kamboju@...aro.org>,
Basil Eljuse <Basil.Eljuse@....com>,
Ferry Toth <fntoth@...il.com>, Arnd Bergmann <arnd@...db.de>,
Anders Roxell <anders.roxell@...aro.org>,
Linux PM <linux-pm@...r.kernel.org>,
Nathan Chancellor <nathan@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH 1/2] driver core: Fix wait_for_device_probe() &
deferred_probe_timeout interaction
On Fri, Jun 3, 2022 at 1:32 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> From: Saravana Kannan <saravanak@...gle.com>
>
> Mounting NFS rootfs was timing out when deferred_probe_timeout was
> non-zero [1]. This was because ip_auto_config() initcall times out
> waiting for the network interfaces to show up when
> deferred_probe_timeout was non-zero. While ip_auto_config() calls
> wait_for_device_probe() to make sure any currently running deferred
> probe work or asynchronous probe finishes, that wasn't sufficient to
> account for devices being deferred until deferred_probe_timeout.
>
> Commit 35a672363ab3 ("driver core: Ensure wait_for_device_probe() waits
> until the deferred_probe_timeout fires") tried to fix that by making
> sure wait_for_device_probe() waits for deferred_probe_timeout to expire
> before returning.
>
> However, if wait_for_device_probe() is called from the kernel_init()
> context:
>
> - Before deferred_probe_initcall() [2], it causes the boot process to
> hang due to a deadlock.
>
> - After deferred_probe_initcall() [3], it blocks kernel_init() from
> continuing till deferred_probe_timeout expires and beats the point of
> deferred_probe_timeout that's trying to wait for userspace to load
> modules.
>
> Neither of this is good. So revert the changes to
> wait_for_device_probe().
>
> [1] - https://lore.kernel.org/lkml/TYAPR01MB45443DF63B9EF29054F7C41FD8C60@TYAPR01MB4544.jpnprd01.prod.outlook.com/
> [2] - https://lore.kernel.org/lkml/YowHNo4sBjr9ijZr@dev-arch.thelio-3990X/
> [3] - https://lore.kernel.org/lkml/Yo3WvGnNk3LvLb7R@linutronix.de/
>
> Fixes: 35a672363ab3 ("driver core: Ensure wait_for_device_probe() waits until the deferred_probe_timeout fires")
> Cc: John Stultz <jstultz@...gle.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>
> Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Andy Shevchenko <andy.shevchenko@...il.com>
> Cc: Sudeep Holla <sudeep.holla@....com>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Cc: Naresh Kamboju <naresh.kamboju@...aro.org>
> Cc: Basil Eljuse <Basil.Eljuse@....com>
> Cc: Ferry Toth <fntoth@...il.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Anders Roxell <anders.roxell@...aro.org>
> Cc: linux-pm@...r.kernel.org
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Reported-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>
> Acked-by: John Stultz <jstultz@...gle.com>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> Link: https://lore.kernel.org/r/20220526034609.480766-2-saravanak@google.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Reviewed-by: Rafael J. Wysocki <rafael@...nel.org>
> ---
> drivers/base/dd.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 2fc8507f59ee..91f63cd33b12 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -263,7 +263,6 @@ int driver_deferred_probe_timeout;
> #endif
>
> EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
> -static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);
>
> static int __init deferred_probe_timeout_setup(char *str)
> {
> @@ -318,7 +317,6 @@ static void deferred_probe_timeout_work_func(struct work_struct *work)
> list_for_each_entry(p, &deferred_probe_pending_list, deferred_probe)
> dev_info(p->device, "deferred probe pending\n");
> mutex_unlock(&deferred_probe_mutex);
> - wake_up_all(&probe_timeout_waitqueue);
> }
> static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
>
> @@ -736,9 +734,6 @@ int driver_probe_done(void)
> */
> void wait_for_device_probe(void)
> {
> - /* wait for probe timeout */
> - wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);
> -
> /* wait for the deferred probe workqueue to finish */
> flush_work(&deferred_probe_work);
>
> --
> 2.36.1
>
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