56 lines
1.9 KiB
Diff
56 lines
1.9 KiB
Diff
From: Ingo Molnar <mingo@elte.hu>
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Date: Fri, 3 Jul 2009 08:30:01 -0500
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Subject: [PATCH] serial: 8250: Clean up the locking for -rt
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.14/patches-3.14.0-rt1.tar.xz
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In -RT the spin_lock_irqsave() does not spin but sleep if the lock is
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taken. Before that, local_irq_save() is invoked which disables
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interrupts even on -RT. Therefore local_irq_save() + spin_lock() does not
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work.
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In the ->sysrq and oops_in_progress case it is save to trylock the lock
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i.e. this is what we do now anyway except for ->sysrq where we assume
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that the lock is already taken.
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The spin_lock_irqsave() grabs the lock and disables the interrupts on
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vanilla (the same behavior) and on -RT it won't disable interrupts.
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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[bigeasy: add a patch description]
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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drivers/tty/serial/8250/8250_core.c | 15 +++++----------
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1 file changed, 5 insertions(+), 10 deletions(-)
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--- a/drivers/tty/serial/8250/8250_core.c
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+++ b/drivers/tty/serial/8250/8250_core.c
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@@ -2882,14 +2882,10 @@ serial8250_console_write(struct console
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touch_nmi_watchdog();
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- local_irq_save(flags);
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- if (port->sysrq) {
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- /* serial8250_handle_irq() already took the lock */
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- locked = 0;
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- } else if (oops_in_progress) {
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- locked = spin_trylock(&port->lock);
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- } else
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- spin_lock(&port->lock);
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+ if (port->sysrq || oops_in_progress)
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+ locked = spin_trylock_irqsave(&port->lock, flags);
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+ else
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+ spin_lock_irqsave(&port->lock, flags);
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/*
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* First save the IER then disable the interrupts
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@@ -2921,8 +2917,7 @@ serial8250_console_write(struct console
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serial8250_modem_status(up);
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if (locked)
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- spin_unlock(&port->lock);
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- local_irq_restore(flags);
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+ spin_unlock_irqrestore(&port->lock, flags);
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}
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static int __init serial8250_console_setup(struct console *co, char *options)
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