[PATCH] serialize assign_irq_vector() use of static variables

[PATCH] serialize assign_irq_vector() use of static variables

[Jan Beulich]

Since assign_irq_vector() can be called at runtime, its access of static
variables should be protected by a lock.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

diff -Npru /home/jbeulich/tmp/linux-2.6.17-rc2/arch/i386/kernel/io_apic.c
2.6.17-rc2-x86-assign_irq_vector-lock/arch/i386/kernel/io_apic.c
--- /home/jbeulich/tmp/linux-2.6.17-rc2/arch/i386/kernel/io_apic.c	2006-04-26 10:55:11.000000000 +0200
+++ 2.6.17-rc2-x86-assign_irq_vector-lock/arch/i386/kernel/io_apic.c	2006-04-25 15:38:32.000000000 +0200
@@ -50,6 +50,7 @@ atomic_t irq_mis_count;
 static struct { int pin, apic; } ioapic_i8259 = { -1, -1 };
 
 static DEFINE_SPINLOCK(ioapic_lock);
+static DEFINE_SPINLOCK(vector_lock);
 
 int timer_over_8254 __initdata = 1;
 
@@ -1152,10 +1153,16 @@ u8 irq_vector[NR_IRQ_VECTORS] __read_mos
 int assign_irq_vector(int irq)
 {
 	static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;
+	int vector;
+
+	BUG_ON(irq != AUTO_ASSIGN && (unsigned)irq >= NR_IRQ_VECTORS);
+
+	spin_lock(&vector_lock);
 
-	BUG_ON(irq >= NR_IRQ_VECTORS);
-	if (irq != AUTO_ASSIGN && IO_APIC_VECTOR(irq) > 0)
+	if (irq != AUTO_ASSIGN && IO_APIC_VECTOR(irq) > 0) {
+		spin_unlock(&vector_lock);
 		return IO_APIC_VECTOR(irq);
+	}
 next:
 	current_vector += 8;
 	if (current_vector == SYSCALL_VECTOR)
@@ -1163,16 +1170,21 @@ next:
 
 	if (current_vector >= FIRST_SYSTEM_VECTOR) {
 		offset++;
-		if (!(offset%8))
+		if (!(offset%8)) {
+			spin_unlock(&vector_lock);
 			return -ENOSPC;
+		}
 		current_vector = FIRST_DEVICE_VECTOR + offset;
 	}
 
-	vector_irq[current_vector] = irq;
+	vector = current_vector;
+	vector_irq[vector] = irq;
 	if (irq != AUTO_ASSIGN)
-		IO_APIC_VECTOR(irq) = current_vector;
+		IO_APIC_VECTOR(irq) = vector;
+
+	spin_unlock(&vector_lock);
 
-	return current_vector;
+	return vector;
 }
 
 static struct hw_interrupt_type ioapic_level_type;
diff -Npru /home/jbeulich/tmp/linux-2.6.17-rc2/arch/x86_64/kernel/io_apic.c
2.6.17-rc2-x86-assign_irq_vector-lock/arch/x86_64/kernel/io_apic.c
--- /home/jbeulich/tmp/linux-2.6.17-rc2/arch/x86_64/kernel/io_apic.c	2006-04-26 10:55:24.000000000 +0200
+++ 2.6.17-rc2-x86-assign_irq_vector-lock/arch/x86_64/kernel/io_apic.c	2006-04-25 15:38:32.000000000 +0200
@@ -56,6 +56,7 @@ int timer_over_8254 __initdata = 0;
 static struct { int pin, apic; } ioapic_i8259 = { -1, -1 };
 
 static DEFINE_SPINLOCK(ioapic_lock);
+static DEFINE_SPINLOCK(vector_lock);
 
 /*
  * # of IRQ routing registers
@@ -814,10 +815,16 @@ u8 irq_vector[NR_IRQ_VECTORS] __read_mos
 int assign_irq_vector(int irq)
 {
 	static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;
+	int vector;
 
 	BUG_ON(irq != AUTO_ASSIGN && (unsigned)irq >= NR_IRQ_VECTORS);
-	if (irq != AUTO_ASSIGN && IO_APIC_VECTOR(irq) > 0)
+
+	spin_lock(&vector_lock);
+
+	if (irq != AUTO_ASSIGN && IO_APIC_VECTOR(irq) > 0) {
+		spin_unlock(&vector_lock);
 		return IO_APIC_VECTOR(irq);
+	}
 next:
 	current_vector += 8;
 	if (current_vector == IA32_SYSCALL_VECTOR)
@@ -829,11 +836,14 @@ next:
 		current_vector = FIRST_DEVICE_VECTOR + offset;
 	}
 
-	vector_irq[current_vector] = irq;
+	vector = current_vector;
+	vector_irq[vector] = irq;
 	if (irq != AUTO_ASSIGN)
-		IO_APIC_VECTOR(irq) = current_vector;
+		IO_APIC_VECTOR(irq) = vector;
+
+	spin_unlock(&vector_lock);
 
-	return current_vector;
+	return vector;
 }
 
 extern void (*interrupt[NR_IRQS])(void);

Re: [PATCH] serialize assign_irq_vector() use of static variables

[Andi Kleen]

On Wednesday 26 April 2006 16:07, Jan Beulich wrote:
> Since assign_irq_vector() can be called at runtime, its access of static
> variables should be protected by a lock.

Applied thanks.

-Andi

Re: [PATCH] serialize assign_irq_vector() use of static variables

[Randy.Dunlap]

On Wed, 26 Apr 2006 16:07:53 +0200 Jan Beulich wrote:

> Since assign_irq_vector() can be called at runtime, its access of static
> variables should be protected by a lock.
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>

Hi,
Would you include diffstat output also, as mentioned (optional)
in Documentation/SubmittingPatches?  I'd really like to see a list
of patched files without having to scan the entire patch.
Thanks.

Oh, the diff filenames should begin at the linux-2.x.y level so
that they can be applied with patch -p1.
Lots of tools know how to do this.

> diff -Npru /home/jbeulich/tmp/linux-2.6.17-rc2/arch/i386/kernel/io_apic.c
> 2.6.17-rc2-x86-assign_irq_vector-lock/arch/i386/kernel/io_apic.c
> --- /home/jbeulich/tmp/linux-2.6.17-rc2/arch/i386/kernel/io_apic.c	2006-04-26 10:55:11.000000000 +0200
> +++ 2.6.17-rc2-x86-assign_irq_vector-lock/arch/i386/kernel/io_apic.c	2006-04-25 15:38:32.000000000 +0200
> @@ -1163,16 +1170,21 @@ next:
>  
>  	if (current_vector >= FIRST_SYSTEM_VECTOR) {
>  		offset++;
> -		if (!(offset%8))
> +		if (!(offset%8)) {

Use better spacing here:  (offset % 8)

> +			spin_unlock(&vector_lock);
>  			return -ENOSPC;
> +		}
>  		current_vector = FIRST_DEVICE_VECTOR + offset;
>  	}
>  

---
~Randy