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

[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
...@@ -2252,10 +2252,14 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count) ...@@ -2252,10 +2252,14 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
touch_nmi_watchdog(); touch_nmi_watchdog();
if (oops_in_progress) { local_irq_save(flags);
locked = spin_trylock_irqsave(&up->port.lock, 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 } else
spin_lock_irqsave(&up->port.lock, flags); spin_lock(&up->port.lock);
/* /*
* First save the IER then disable the interrupts * First save the IER then disable the interrupts
...@@ -2277,7 +2281,8 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count) ...@@ -2277,7 +2281,8 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
serial_out(up, UART_IER, ier); serial_out(up, UART_IER, ier);
if (locked) 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) static int serial8250_console_setup(struct console *co, char *options)
......
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