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serial 8250: sysrq deadlock fix

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

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

Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Andrew Morton
2006-07-06 23:59:50 -07:00
committed by Greg Kroah-Hartman
parent 7eb9908486
commit 44896b17f1
1 changed files with 9 additions and 4 deletions
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drivers/serial/8250.c
+9 -4
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@@ -2241,10 +2241,14 @@ 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
@@ -2266,7 +2270,8 @@ 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)