From: Eric W. Biederman <ebiederm@xmission.com>
Date: Wed, 4 Oct 2006 09:16:49 +0000 (-0700)
Subject: [PATCH] genirq: irq: generalize the check for HARDIRQ_BITS
X-Git-Tag: v2.6.19-rc1~70
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=23d0b8b053391afe15c9667d80de77ca88e18b8b;p=linux-2.6

[PATCH] genirq: irq: generalize the check for HARDIRQ_BITS

This patch adds support for systems that cannot receive every interrupt on a
single cpu simultaneously, in the check to see if we have enough HARDIRQ_BITS.

MAX_HARDIRQS_PER_CPU becomes the count of the maximum number of hardare
generated interrupts per cpu.

On architectures that support per cpu interrupt delivery this can be a
significant space savings and scalability bonus.

This patch adds support for systems that cannot receive every interrupt on

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rajesh Shah <rajesh.shah@intel.com>
Cc: Andi Kleen <ak@muc.de>
Cc: "Protasevich, Natalie" <Natalie.Protasevich@UNISYS.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/include/asm-x86_64/hardirq.h b/include/asm-x86_64/hardirq.h
index 64a65ce2f4..95d5e090ed 100644
--- a/include/asm-x86_64/hardirq.h
+++ b/include/asm-x86_64/hardirq.h
@@ -6,6 +6,9 @@
 #include <asm/pda.h>
 #include <asm/apic.h>
 
+/* We can have at most NR_VECTORS irqs routed to a cpu at a time */
+#define MAX_HARDIRQS_PER_CPU NR_VECTORS
+
 #define __ARCH_IRQ_STAT 1
 
 #define local_softirq_pending() read_pda(__softirq_pending)
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 50d8b5744c..612472aaa7 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -28,11 +28,16 @@
 
 #ifndef HARDIRQ_BITS
 #define HARDIRQ_BITS	12
+
+#ifndef MAX_HARDIRQS_PER_CPU
+#define MAX_HARDIRQS_PER_CPU NR_IRQS
+#endif
+
 /*
  * The hardirq mask has to be large enough to have space for potentially
  * all IRQ sources in the system nesting on a single CPU.
  */
-#if (1 << HARDIRQ_BITS) < NR_IRQS
+#if (1 << HARDIRQ_BITS) < MAX_HARDIRQS_PER_CPU
 # error HARDIRQ_BITS is too low!
 #endif
 #endif