linux-kernel - [2/3] unconditional i386 IRQ stacks

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Message-ID: <20070430233712.GI26598@holomorphy.com>
Date:	Mon, 30 Apr 2007 16:37:12 -0700
From:	Bill Irwin <bill.irwin@...cle.com>
To:	Bill Irwin <bill.irwin@...cle.com>
Cc:	linux-kernel@...r.kernel.org, bunk@...sta.de, akpm@...l.org,
	gcoady@...il.com, zlynx@....org, dgc@....com,
	alan@...rguk.ukuu.org.uk, andi@...stfloor.org, hch@...radead.org,
	jengelh@...ux01.gwdg.de, zwane@...radead.org, neilb@...e.de,
	jens.axboe@...cle.com, eric@...venscaling.com, wli@...omorphy.com
Subject: [2/3] unconditional i386 IRQ stacks

IRQ stacks are a valuable stability feature. This patch makes them
unconditional, as there is no circumstance under which they do not
improve stability and they have no meaningful performance impact.

Signed-off-by: William Irwin <bill.irwin@...cle.com>


Index: stack-paranoia/include/asm-i386/irq.h
===================================================================
--- stack-paranoia.orig/include/asm-i386/irq.h	2007-04-30 14:29:14.390652748 -0700
+++ stack-paranoia/include/asm-i386/irq.h	2007-04-30 14:32:46.742754004 -0700
@@ -24,14 +24,9 @@
 # define ARCH_HAS_NMI_WATCHDOG		/* See include/linux/nmi.h */
 #endif
 
-#ifdef CONFIG_4KSTACKS
-  extern void irq_ctx_init(int cpu);
-  extern void irq_ctx_exit(int cpu);
-# define __ARCH_HAS_DO_SOFTIRQ
-#else
-# define irq_ctx_init(cpu) do { } while (0)
-# define irq_ctx_exit(cpu) do { } while (0)
-#endif
+void irq_ctx_init(int);
+void irq_ctx_exit(int);
+#define __ARCH_HAS_DO_SOFTIRQ
 
 #ifdef CONFIG_IRQBALANCE
 extern int irqbalance_disable(char *str);
Index: stack-paranoia/arch/i386/kernel/irq.c
===================================================================
--- stack-paranoia.orig/arch/i386/kernel/irq.c	2007-04-30 14:31:14.717509785 -0700
+++ stack-paranoia/arch/i386/kernel/irq.c	2007-04-30 14:43:02.869865087 -0700
@@ -49,7 +49,6 @@
 #endif
 }
 
-#ifdef CONFIG_4KSTACKS
 /*
  * per-CPU IRQ handling contexts (thread information and stack)
  */
@@ -60,7 +59,6 @@
 
 static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
 static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);
-#endif
 
 /*
  * do_IRQ handles all normal device IRQ's (the special
@@ -73,10 +71,8 @@
 	/* high bit used in ret_from_ code */
 	int irq = ~regs->orig_eax;
 	struct irq_desc *desc = irq_desc + irq;
-#ifdef CONFIG_4KSTACKS
 	union irq_ctx *curctx, *irqctx;
 	u32 *isp;
-#endif
 
 	if (unlikely((unsigned)irq >= NR_IRQS)) {
 		printk(KERN_EMERG "%s: cannot handle IRQ %d\n",
@@ -100,9 +96,6 @@
 		}
 	}
 #endif
-
-#ifdef CONFIG_4KSTACKS
-
 	curctx = (union irq_ctx *) current_thread_info();
 	irqctx = per_cpu(hardirq_ctx, smp_processor_id());
 
@@ -138,7 +131,6 @@
 			: "memory", "cc"
 		);
 	} else
-#endif
 		desc->handle_irq(irq, desc);
 
 	irq_exit();
@@ -146,8 +138,6 @@
 	return 1;
 }
 
-#ifdef CONFIG_4KSTACKS
-
 /*
  * These should really be __section__(".bss.page_aligned") as well, but
  * gcc's 3.0 and earlier don't handle that correctly.
@@ -251,7 +241,6 @@
 }
 
 EXPORT_SYMBOL(do_softirq);
-#endif
 
 /*
  * Interrupt statistics:
-
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