From: Ingo Molnar <mingo@xxxxxxx>
In -RT the spin_lock_irqsave() does not spin but sleep if the lock is
taken. Before that, local_irq_save() is invoked which disables
interrupts even on -RT. Therefore local_irq_save() + spin_lock() does not
work.
In the ->sysrq and oops_in_progress case it is save to trylock the lock
i.e. this is what we do now anyway except for ->sysrq where we assume
that the lock is already taken.
The spin_lock_irqsave() grabs the lock and disables the interrupts on
vanilla (the same behavior) and on -RT it won't disable interrupts.
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bigeasy: add a patch description]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_core.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 747073b..81f909c 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -2886,14 +2886,10 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
touch_nmi_watchdog();
- local_irq_save(flags);
- if (port->sysrq) {
- /* serial8250_handle_irq() already took the lock */
- locked = 0;
- } else if (oops_in_progress) {
- locked = spin_trylock(&port->lock);
- } else
- spin_lock(&port->lock);
+ if (port->sysrq || oops_in_progress)
+ locked = spin_trylock_irqsave(&port->lock, flags);
+ else
+ spin_lock_irqsave(&port->lock, flags);
/*
* First save the IER then disable the interrupts
@@ -2925,8 +2921,7 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
serial8250_modem_status(up);
if (locked)
- spin_unlock(&port->lock);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&port->lock, flags);
}
static int __init serial8250_console_setup(struct console *co, char *options)
--
1.9.0
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