From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Stable Team <stable@kernel.org>, Greg KH <greg@kroah.com>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Andrew Morton <akpm@osdl.org>, Andi Kleen <ak@suse.de>,
Ingo Molnar <mingo@elte.hu>, Ralf Baechle <ralf@linux-mips.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Richard Henderson <rth@twiddle.net>
Subject: [PATCH] INPUT: Sanitize PIT locking in pcspkr
Date: Thu, 17 May 2007 15:36:02 +0200 [thread overview]
Message-ID: <1179408962.3764.72.camel@chaos> (raw)
The PC-speaker code has a quite creative method to serialize access to
the PIT: It uses a local lock.
On i386 and x86_64 the access to the PIT is serialized by a lock in the
architecture code. The separate locking in the PC-speaker code ignores
the global lock and creates a nasty race between the PC-speaker and the
PIT clock source / events code on SMP machines.
Use the global i8253_lock instead of the local i8253_beep_lock, when
compiled for i386/x86_64.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Index: linux-2.6/arch/x86_64/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/x86_64/kernel/time.c
+++ linux-2.6/arch/x86_64/kernel/time.c
@@ -33,6 +33,7 @@
#include <acpi/acpi_bus.h>
#endif
#include <asm/8253pit.h>
+#include <asm/i8253.h>
#include <asm/pgtable.h>
#include <asm/vsyscall.h>
#include <asm/timex.h>
@@ -50,6 +51,7 @@ static char *timename = NULL;
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
DEFINE_SPINLOCK(i8253_lock);
+EXPORT_SYMBOL(i8253_lock);
volatile unsigned long __jiffies __section_jiffies = INITIAL_JIFFIES;
Index: linux-2.6/drivers/input/misc/pcspkr.c
===================================================================
--- linux-2.6.orig/drivers/input/misc/pcspkr.c
+++ linux-2.6/drivers/input/misc/pcspkr.c
@@ -24,7 +24,12 @@ MODULE_AUTHOR("Vojtech Pavlik <vojtech@u
MODULE_DESCRIPTION("PC Speaker beeper driver");
MODULE_LICENSE("GPL");
-static DEFINE_SPINLOCK(i8253_beep_lock);
+#ifdef CONFIG_X86
+/* Use the global PIT lock ! */
+#include <asm/i8253.h>
+#else
+static DEFINE_SPINLOCK(i8253_lock);
+#endif
static int pcspkr_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)
{
@@ -43,7 +48,7 @@ static int pcspkr_event(struct input_dev
if (value > 20 && value < 32767)
count = PIT_TICK_RATE / value;
- spin_lock_irqsave(&i8253_beep_lock, flags);
+ spin_lock_irqsave(&i8253_lock, flags);
if (count) {
/* enable counter 2 */
@@ -58,7 +63,7 @@ static int pcspkr_event(struct input_dev
outb(inb_p(0x61) & 0xFC, 0x61);
}
- spin_unlock_irqrestore(&i8253_beep_lock, flags);
+ spin_unlock_irqrestore(&i8253_lock, flags);
return 0;
}
Index: linux-2.6/include/asm-x86_64/i8253.h
===================================================================
--- /dev/null
+++ linux-2.6/include/asm-x86_64/i8253.h
@@ -0,0 +1,6 @@
+#ifndef __ASM_I8253_H__
+#define __ASM_I8253_H__
+
+extern spinlock_t i8253_lock;
+
+#endif /* __ASM_I8253_H__ */
next reply other threads:[~2007-05-17 13:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-17 13:36 Thomas Gleixner [this message]
2007-05-17 14:15 ` [PATCH] INPUT: Sanitize PIT locking in pcspkr Dmitry Torokhov
2007-05-17 14:35 ` Thomas Gleixner
2007-05-17 14:36 ` Dmitry Torokhov
2007-05-17 14:49 ` Thomas Gleixner
2007-05-18 4:27 ` Andi Kleen
2007-05-18 6:26 ` Dmitry Torokhov
2007-06-12 0:27 ` [stable] " Chris Wright
2007-06-12 5:50 ` Dmitry Torokhov
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