| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.18 237/339] drivers: usb: host: Fix deadlock in oxu_bus_suspend() | Date | Mon, 13 Jun 2022 12:11:02 +0200 |
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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 b741670525e3..ee403df33093 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
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