Subject: make IRQ stacks independently configurable

Divorce IRQ stack configuration from CONFIG_4KSTACKS, as it's believed to
be an important safety measure regardless of stack size by some users.


Index: linux-2.6/arch/i386/kernel/irq.c
===================================================================
--- linux-2.6.orig/arch/i386/kernel/irq.c	2007-03-03 20:49:06.000000000 -0800
+++ linux-2.6/arch/i386/kernel/irq.c	2007-03-03 23:43:43.000000000 -0800
@@ -47,7 +47,7 @@
 #endif
 }
 
-#ifdef CONFIG_4KSTACKS
+#ifdef CONFIG_IRQSTACKS
 /*
  * per-CPU IRQ handling contexts (thread information and stack)
  */
@@ -71,7 +71,7 @@
 	/* high bit used in ret_from_ code */
 	int irq = ~regs->orig_eax;
 	struct irq_desc *desc = irq_desc + irq;
-#ifdef CONFIG_4KSTACKS
+#ifdef CONFIG_IRQSTACKS
 	union irq_ctx *curctx, *irqctx;
 	u32 *isp;
 #endif
@@ -99,7 +99,7 @@
 	}
 #endif
 
-#ifdef CONFIG_4KSTACKS
+#ifdef CONFIG_IRQSTACKS
 
 	curctx = (union irq_ctx *) current_thread_info();
 	irqctx = hardirq_ctx[smp_processor_id()];
@@ -144,7 +144,7 @@
 	return 1;
 }
 
-#ifdef CONFIG_4KSTACKS
+#ifdef CONFIG_IRQSTACKS
 
 /*
  * These should really be __section__(".bss.page_aligned") as well, but
Index: linux-2.6/include/asm-i386/irq.h
===================================================================
--- linux-2.6.orig/include/asm-i386/irq.h	2007-03-03 20:49:06.000000000 -0800
+++ linux-2.6/include/asm-i386/irq.h	2007-03-03 21:03:26.000000000 -0800
@@ -24,7 +24,7 @@
 # define ARCH_HAS_NMI_WATCHDOG		/* See include/linux/nmi.h */
 #endif
 
-#ifdef CONFIG_4KSTACKS
+#ifdef CONFIG_IRQSTACKS
   extern void irq_ctx_init(int cpu);
   extern void irq_ctx_exit(int cpu);
 # define __ARCH_HAS_DO_SOFTIRQ
Index: linux-2.6/arch/i386/Kconfig.debug
===================================================================
--- linux-2.6.orig/arch/i386/Kconfig.debug	2007-03-03 20:49:10.000000000 -0800
+++ linux-2.6/arch/i386/Kconfig.debug	2007-03-03 23:44:56.000000000 -0800
@@ -35,6 +35,14 @@
 
 	  This option will slow down process creation somewhat.
 
+config IRQSTACKS
+	bool "IRQ stacks"
+	depends on DEBUG_KERNEL
+	help
+	  Arranges for per-cpu interrupt stacks so that interrupts
+	  and interrupt-time processing don't consume space on task
+	  stacks.
+
 config VMALLOC_STACK
 	bool "vmalloc() the stack"
 	depends on DEBUG_KERNEL
@@ -76,8 +84,7 @@
 	  If you say Y here the kernel will use a 4Kb stacksize for the
 	  kernel stack attached to each process/thread. This facilitates
 	  running more threads on a system and also reduces the pressure
-	  on the VM subsystem for higher order allocations. This option
-	  will also use IRQ stacks to compensate for the reduced stackspace.
+	  on the VM subsystem for higher order allocations.
 
 config 8KSTACKS
 	bool "Use 8KB for kernel stacks"
@@ -90,7 +97,6 @@
 	  If you say Y here, the kernel will use a 16KB stacksize.
 	  This impedes running more threads on a system and also increases
 	  the pressure on the VM subsystem for higher order allocations.
-	  This option will also use IRQ stacks to for additional safety.
 
 config 32KSTACKS
 	bool "Use 32KB for kernel stacks"
@@ -98,15 +104,14 @@
 	  If you say Y here, the kernel will use a 32KB stacksize.
 	  This impedes running more threads on a system and also increases
 	  the pressure on the VM subsystem for higher order allocations.
-	  This option will also use IRQ stacks to for additional safety.
 
 config 64KSTACKS
 	bool "Use 64KB for kernel stacks"
+	depends on !IRQSTACKS
 	help
 	  If you say Y here, the kernel will use a 64KB stacksize.
 	  This impedes running more threads on a system and also increases
 	  the pressure on the VM subsystem for higher order allocations.
-	  This option will also use IRQ stacks to for additional safety.
 
 endchoice
 
Index: linux-2.6/include/asm-i386/module.h
===================================================================
--- linux-2.6.orig/include/asm-i386/module.h	2007-03-03 20:49:10.000000000 -0800
+++ linux-2.6/include/asm-i386/module.h	2007-03-03 21:03:26.000000000 -0800
@@ -80,7 +80,13 @@
 #define MODULE_VMALLOC_STACK ""
 #endif
 
+#ifdef CONFIG_IRQSTACKS
+#define MODULE_IRQSTACKS "IRQSTACKS "
+#else
+#define MODULE_IRQSTACKS ""
+#endif
+
 #define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY MODULE_STACKSIZE \
-		MODULE_VMALLOC_STACK
+		MODULE_VMALLOC_STACK MODULE_IRQSTACKS
 
 #endif /* _ASM_I386_MODULE_H */