[PATCH AUTOSEL 5.17 14/60] drivers: usb: host: Fix deadlock in oxu_bus_suspend()

Sasha Levin
2022-06-07T18:58:08Z

From: Duoming Zhou <duoming@zju.edu.cn>

[ Upstream commit 4d378f2ae58138d4c55684e1d274e7dd94aa6524 ]

There is a deadlock in oxu_bus_suspend(), which is shown below:

(Thread 1) | (Thread 2)
| timer_action()
oxu_bus_suspend() | mod_timer()
spin_lock_irq() //(1) | (wait a time)
... | oxu_watchdog()
del_timer_sync() | spin_lock_irq() //(2)
(wait timer to stop) | ...

We hold oxu->lock in position (1) of thread 1, and use
del_timer_sync() to wait timer to stop, but timer handler
also need oxu->lock in position (2) of thread 2. As a result,
oxu_bus_suspend() will block forever.

This patch extracts del_timer_sync() from the protection of
spin_lock_irq(), which could let timer handler to obtain
the needed lock.

Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220417120305.64577-1-duoming@zju.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/usb/host/oxu210hp-hcd.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/usb/host/oxu210hp-hcd.c b/drivers/usb/host/oxu210hp-hcd.c
index e82ff2a49672..4f5498521e1b 100644
--- a/drivers/usb/host/oxu210hp-hcd.c
+++ b/drivers/usb/host/oxu210hp-hcd.c
@@ -3909,8 +3909,10 @@ static int oxu_bus_suspend(struct usb_hcd *hcd)
}
}

+ spin_unlock_irq(&oxu->lock);
/* turn off now-idle HC */
del_timer_sync(&oxu->watchdog);
+ spin_lock_irq(&oxu->lock);
ehci_halt(oxu);
hcd->state = HC_STATE_SUSPENDED;

--
2.35.1