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Subject: drivers-tty-pl011-irq-disable-madness.patch
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 08 Jan 2013 21:36:51 +0100
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
drivers/tty/serial/amba-pl011.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
Index: linux-stable/drivers/tty/serial/amba-pl011.c
===================================================================
--- linux-stable.orig/drivers/tty/serial/amba-pl011.c
+++ linux-stable/drivers/tty/serial/amba-pl011.c
@@ -1737,13 +1737,19 @@ pl011_console_write(struct console *co,
clk_enable(uap->clk);
- local_irq_save(flags);
+ /*
+ * local_irq_save(flags);
+ *
+ * This local_irq_save() is nonsense. If we come in via sysrq
+ * handling then interrupts are already disabled. Aside of
+ * that the port.sysrq check is racy on SMP regardless.
+ */
if (uap->port.sysrq)
locked = 0;
else if (oops_in_progress)
- locked = spin_trylock(&uap->port.lock);
+ locked = spin_trylock_irqsave(&uap->port.lock, flags);
else
- spin_lock(&uap->port.lock);
+ spin_lock_irqsave(&uap->port.lock, flags);
/*
* First save the CR then disable the interrupts
@@ -1765,8 +1771,7 @@ pl011_console_write(struct console *co,
writew(old_cr, uap->port.membase + UART011_CR);
if (locked)
- spin_unlock(&uap->port.lock);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&uap->port.lock, flags);
clk_disable(uap->clk);
}
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