Commit abf1e0a9 authored by Stefan Agner's avatar Stefan Agner Committed by Greg Kroah-Hartman

tty: serial: fsl_lpuart: lock port on console write

The console write code is not entirely race free (e.g. the operations
to disabling the UART interrupts are not atomic) hence locking is
required. This has been become apparent with the PREEMPT RT patchset
applied: With the fully preemptible kernel configuration the system
often ended up in a freeze already at startup.

Disable interrupts and lock using read_lock_irqsave. Try to lock in
the sysrq/oops case, but don't bother if locking fails.
Signed-off-by: default avatarStefan Agner <stefan@agner.ch>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4d9d7d89
...@@ -1705,6 +1705,13 @@ lpuart_console_write(struct console *co, const char *s, unsigned int count) ...@@ -1705,6 +1705,13 @@ lpuart_console_write(struct console *co, const char *s, unsigned int count)
{ {
struct lpuart_port *sport = lpuart_ports[co->index]; struct lpuart_port *sport = lpuart_ports[co->index];
unsigned char old_cr2, cr2; unsigned char old_cr2, cr2;
unsigned long flags;
int locked = 1;
if (sport->port.sysrq || oops_in_progress)
locked = spin_trylock_irqsave(&sport->port.lock, flags);
else
spin_lock_irqsave(&sport->port.lock, flags);
/* first save CR2 and then disable interrupts */ /* first save CR2 and then disable interrupts */
cr2 = old_cr2 = readb(sport->port.membase + UARTCR2); cr2 = old_cr2 = readb(sport->port.membase + UARTCR2);
...@@ -1719,6 +1726,9 @@ lpuart_console_write(struct console *co, const char *s, unsigned int count) ...@@ -1719,6 +1726,9 @@ lpuart_console_write(struct console *co, const char *s, unsigned int count)
barrier(); barrier();
writeb(old_cr2, sport->port.membase + UARTCR2); writeb(old_cr2, sport->port.membase + UARTCR2);
if (locked)
spin_unlock_irqrestore(&sport->port.lock, flags);
} }
static void static void
...@@ -1726,6 +1736,13 @@ lpuart32_console_write(struct console *co, const char *s, unsigned int count) ...@@ -1726,6 +1736,13 @@ lpuart32_console_write(struct console *co, const char *s, unsigned int count)
{ {
struct lpuart_port *sport = lpuart_ports[co->index]; struct lpuart_port *sport = lpuart_ports[co->index];
unsigned long old_cr, cr; unsigned long old_cr, cr;
unsigned long flags;
int locked = 1;
if (sport->port.sysrq || oops_in_progress)
locked = spin_trylock_irqsave(&sport->port.lock, flags);
else
spin_lock_irqsave(&sport->port.lock, flags);
/* first save CR2 and then disable interrupts */ /* first save CR2 and then disable interrupts */
cr = old_cr = lpuart32_read(sport->port.membase + UARTCTRL); cr = old_cr = lpuart32_read(sport->port.membase + UARTCTRL);
...@@ -1740,6 +1757,9 @@ lpuart32_console_write(struct console *co, const char *s, unsigned int count) ...@@ -1740,6 +1757,9 @@ lpuart32_console_write(struct console *co, const char *s, unsigned int count)
barrier(); barrier();
lpuart32_write(old_cr, sport->port.membase + UARTCTRL); lpuart32_write(old_cr, sport->port.membase + UARTCTRL);
if (locked)
spin_unlock_irqrestore(&sport->port.lock, flags);
} }
/* /*
......
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