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Commit 68aa2c0d authored by Andrew Morton's avatar Andrew Morton Committed by Russell King
Browse files

[SERIAL] 8250: sysrq deadlock fix 

Fix http://bugzilla.kernel.org/show_bug.cgi?id=6716



Doing a sysrq over a serial line into an SMP machine presently deadlocks.

Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 3be91ec7

drivers/serial/8250.c

+9 −4
Original line number Diff line number Diff line
@@ -2252,10 +2252,14 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count) 


	touch_nmi_watchdog();



	if (oops_in_progress) {

		locked = spin_trylock_irqsave(&up->port.lock, flags);

	local_irq_save(flags);

	if (up->port.sysrq) {

		/* serial8250_handle_port() already took the lock */

		locked = 0;

	} else if (oops_in_progress) {

		locked = spin_trylock(&up->port.lock);

	} else

		spin_lock_irqsave(&up->port.lock, flags);

		spin_lock(&up->port.lock);



	/*

	 *	First save the IER then disable the interrupts
@@ -2277,7 +2281,8 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count) 
	serial_out(up, UART_IER, ier);



	if (locked)

		spin_unlock_irqrestore(&up->port.lock, flags);

		spin_unlock(&up->port.lock);

	local_irq_restore(flags);

}



static int serial8250_console_setup(struct console *co, char *options)