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tty/hvc_console: fix console lock ordering with spinlock 

hvc_remove() takes a spin lock first then acquires the console
semaphore. This situation can easily lead to a deadlock scenario
where we call scheduler with spin lock held.

Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Denis Kirjanov 2017-03-30 10:06:19 -04:00 committed by Greg Kroah-Hartman
parent 93857edd98
commit 19fa6e601b
1 changed files with 2 additions and 2 deletions
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4
drivers/tty/hvc/hvc_console.c
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@ -920,17 +920,17 @@ int hvc_remove(struct hvc_struct *hp)
tty = tty_port_tty_get(&hp->port);
console_lock();
spin_lock_irqsave(&hp->lock, flags);
if (hp->index < MAX_NR_HVC_CONSOLES) {
console_lock();
vtermnos[hp->index] = -1;
cons_ops[hp->index] = NULL;
console_unlock();
}
/* Don't whack hp->irq because tty_hangup() will need to free the irq. */
spin_unlock_irqrestore(&hp->lock, flags);
console_unlock();
/*
* We 'put' the instance that was grabbed when the kref instance