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Subject[3/6] make IRQ stacks independently configurable (was: Re: [-mm patch] i386: enable 4k stacks by default)
On Mon, Apr 30, 2007 at 10:38:19AM -0700, William Lee Irwin III wrote:
> Here's what I did for i386 for someone concerned about blowing the stack.

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

Signed-off-by: William Irwin <wli@holomorphy.com>


Index: stack-paranoia/arch/i386/Kconfig.debug
===================================================================
--- stack-paranoia.orig/arch/i386/Kconfig.debug 2007-04-30 10:32:56.182682722 -0700
+++ stack-paranoia/arch/i386/Kconfig.debug 2007-04-30 10:34:07.058721717 -0700
@@ -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: stack-paranoia/arch/i386/kernel/irq.c
===================================================================
--- stack-paranoia.orig/arch/i386/kernel/irq.c 2007-04-30 10:26:15.967875780 -0700
+++ stack-paranoia/arch/i386/kernel/irq.c 2007-04-30 10:34:07.058721717 -0700
@@ -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: stack-paranoia/include/asm-i386/irq.h
===================================================================
--- stack-paranoia.orig/include/asm-i386/irq.h 2007-04-30 10:26:31.904783972 -0700
+++ stack-paranoia/include/asm-i386/irq.h 2007-04-30 10:34:07.058721717 -0700
@@ -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: stack-paranoia/include/asm-i386/module.h
===================================================================
--- stack-paranoia.orig/include/asm-i386/module.h 2007-04-30 10:32:56.182682722 -0700
+++ stack-paranoia/include/asm-i386/module.h 2007-04-30 10:34:07.058721717 -0700
@@ -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 */
-
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