* [PATCH v1 1/2] driver core: Fix wait_for_device_probe() & deferred_probe_timeout interaction
[not found] <20220526034609.480766-1-saravanak@google.com>
@ 2022-05-26 3:46 ` Saravana Kannan
2022-05-26 4:04 ` John Stultz
0 siblings, 1 reply; 2+ messages in thread
From: Saravana Kannan @ 2022-05-26 3:46 UTC (permalink / raw)
To: Greg Kroah-Hartman, Rafael J. Wysocki, John Stultz, Mark Brown,
Rob Herring, Saravana Kannan
Cc: kernel-team, linux-kernel, John Stultz, David S. Miller,
Alexey Kuznetsov, Hideaki YOSHIFUJI, Jakub Kicinski,
Rafael J . Wysocki, Geert Uytterhoeven, Yoshihiro Shimoda,
Robin Murphy, Andy Shevchenko, Sudeep Holla, Andy Shevchenko,
Naresh Kamboju, Basil Eljuse, Ferry Toth, Arnd Bergmann,
Anders Roxell, linux-pm, Nathan Chancellor,
Sebastian Andrzej Siewior
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/
Cc: John Stultz <jstultz@google.com>
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: 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: Robin Murphy <robin.murphy@arm.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Basil Eljuse <Basil.Eljuse@arm.com>
Cc: Ferry Toth <fntoth@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: linux-pm@vger.kernel.org
Fixes: 35a672363ab3 ("driver core: Ensure wait_for_device_probe() waits until the deferred_probe_timeout fires")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Saravana Kannan <saravanak@google.com>
---
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);
--
2.36.1.124.g0e6072fb45-goog
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