RE: [PATCH 1/4] x86_64 io_apic: Implement remove_pin_to_irq

RE: [PATCH 1/4] x86_64 io_apic: Implement remove_pin_to_irq

[Lu, Yinghai]

-----Original Message-----
From: ebiederm@xmission.com [mailto:ebiederm@xmission.com] 
Sent: Monday, January 08, 2007 1:31 PM
To: Lu, Yinghai
Cc: Linus Torvalds; Tobias Diedrich; Andrew Morton; Adrian Bunk; Andi
Kleen; Linux Kernel Mailing List
Subject: Re: [PATCH 1/4] x86_64 io_apic: Implement remove_pin_to_irq

>Any updates to add_pin_to_irq are wrong.  It works fine.  If there
>is something wrong we need to fix remove_pin_to_irq.

>What is the problem you see?  Sorry I'm dense at the moment.

+static int check_timer_pin(int apic, int pin) {
+	int irq, idx;
+	/* 
+	 * Test the architecture default i8254 timer pin
+	 * of apic 0 pin 2.
+	 */
+
+
+	/* If the apic pin pair is in use by another irq fail */
+	irq = irq_from_pin(apic, pin);
+	if ((irq != -1) && (irq != 0)) {
+		apic_printk(APIC_VERBOSE,KERN_INFO "...apic %d pin % in
use by irq %d\n",
+			apic, pin, irq);
+		return 0; 
+	}
+
+	/* Add an entry in mp_irqs for irq 0 */
+	idx = update_irq0_entry(apic, pin);
+
+	/* Add an entry in irq_to_pin */
+	add_pin_to_irq(0, apic, pin);
+
+	/* Now setup the irq */
+	setup_IO_APIC_irq(apic, pin, idx, 0);
+
+	/* And finally check to see if the irq works */
+	return do_check_timer_pin(apic, pin);
+}
+

In the check_timer_pin, irq_from_pin could return 0, it mean some entry
is for IRQ0 already.
The add_pin_to_irq could add another same entry for it again.

YH

[PATCH] x86_64 ioapic: check_timer_pin Don't add_pin_to_irq if it is already there.

[Eric W. Biederman]

"Lu, Yinghai" <yinghai.lu@amd.com> writes:

>>Any updates to add_pin_to_irq are wrong.  It works fine.  If there
>>is something wrong we need to fix remove_pin_to_irq.
>
>>What is the problem you see?  Sorry I'm dense at the moment.

> In the check_timer_pin, irq_from_pin could return 0, it mean some entry
> is for IRQ0 already.
> The add_pin_to_irq could add another same entry for it again.

Yep.  My oversight.  Here is the trivial patch to fix it.  I don't
see how we could hit this case but if we are going to allow for it
we should handle it correctly.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 arch/x86_64/kernel/io_apic.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index 4891959..cc8e9a4 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -1687,7 +1687,8 @@ static int check_timer_pin(int apic, int pin)
 	idx = update_irq0_entry(apic, pin);
 
 	/* Add an entry in irq_to_pin */
-	add_pin_to_irq(0, apic, pin);
+	if (irq != 0)
+		add_pin_to_irq(0, apic, pin);
 
 	/* Now setup the irq */
 	setup_IO_APIC_irq(apic, pin, idx, 0);
-- 
1.4.4.1.g278f

RE: [PATCH] x86_64 ioapic: check_timer_pin Don't add_pin_to_irq if it is already there.

[Lu, Yinghai]

-----Original Message-----
From: ebiederm@xmission.com [mailto:ebiederm@xmission.com] 
Sent: Monday, January 08, 2007 2:50 PM
To: Andrew Morton
Cc: Linus Torvalds; Tobias Diedrich; Adrian Bunk; Andi Kleen; Linux
Kernel Mailing List; Lu, Yinghai
Subject: [PATCH] x86_64 ioapic: check_timer_pin Don't add_pin_to_irq if
it is already there.

>Yep.  My oversight.  Here is the trivial patch to fix it.  I don't
>see how we could hit this case but if we are going to allow for it
>we should handle it correctly.

Yes, in your check_timer calling sequence, at that point irq can not be
0.
( remove_irq_to_pin already remove that entry).

Or in check_timer_pin

+	if ((irq != -1) && (irq != 0)) {

==>

+	if (irq != -1) {

YH