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drivers: usb: host: Fix deadlock in oxu_bus_suspend()
[ Upstream commit 4d378f2ae5
]
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>
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1 changed files with 2 additions and 0 deletions
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@ -3909,8 +3909,10 @@ static int oxu_bus_suspend(struct usb_hcd *hcd)
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}
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}
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spin_unlock_irq(&oxu->lock);
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/* turn off now-idle HC */
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del_timer_sync(&oxu->watchdog);
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spin_lock_irq(&oxu->lock);
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ehci_halt(oxu);
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hcd->state = HC_STATE_SUSPENDED;
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