From 5ee76c256e928455212ab759c51d198fedbe7523 Mon Sep 17 00:00:00 2001 From: Saravana Kannan Date: Fri, 3 Jun 2022 13:31:37 +0200 Subject: [PATCH] driver core: Fix wait_for_device_probe() & deferred_probe_timeout interaction 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 Cc: "David S. Miller" Cc: Alexey Kuznetsov Cc: Hideaki YOSHIFUJI Cc: Jakub Kicinski Cc: Rob Herring Cc: Geert Uytterhoeven Cc: Yoshihiro Shimoda Cc: Robin Murphy Cc: Andy Shevchenko Cc: Sudeep Holla Cc: Andy Shevchenko Cc: Naresh Kamboju Cc: Basil Eljuse Cc: Ferry Toth Cc: Arnd Bergmann Cc: Anders Roxell Cc: linux-pm@vger.kernel.org Reported-by: Nathan Chancellor Reported-by: Sebastian Andrzej Siewior Tested-by: Geert Uytterhoeven Acked-by: John Stultz Signed-off-by: Saravana Kannan Link: https://lore.kernel.org/r/20220526034609.480766-2-saravanak@google.com Signed-off-by: Greg Kroah-Hartman Reviewed-by: Rafael J. Wysocki Signed-off-by: Linus Torvalds --- drivers/base/dd.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 5443b09eef8b..f963d9010d7f 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); @@ -738,9 +736,6 @@ 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); -- 2.39.5