2004-10-04 11:45:31

by Oleg Nesterov

Subject: [PATCH] kill thread_info.previous_esp

Hello.

current_stack_pointer() can be saved in irq_ctx->stack after stack
switching.

Personally, i think it is a more natural way. It is a matter of taste,
of course, so feel free to ignore this.

This irq_previous_esp() is based on Kirill's is_irq_stack_ptr() idea.

On top of the "alternate stack dump fix", see
http://marc.theaimsgroup.com/?l=linux-kernel&m=109687808210397

Oleg.

Signed-off-by: Oleg Nesterov <[email protected]>

diff -rup rc3-mm1-trace/arch/i386/kernel/irq.c rc3-mm1-noesp/arch/i386/kernel/irq.c
--- rc3-mm1-trace/arch/i386/kernel/irq.c 2004-10-04 10:38:06.000000000 +0400
+++ rc3-mm1-noesp/arch/i386/kernel/irq.c 2004-10-04 14:49:45.000000000 +0400
@@ -74,8 +74,8 @@ asmlinkage unsigned int do_IRQ(struct pt
/* build the stack frame on the IRQ stack */
isp = (u32*) ((char*)irqctx + sizeof(*irqctx));
irqctx->tinfo.task = curctx->tinfo.task;
- irqctx->tinfo.previous_esp = current_stack_pointer();

+ *--isp = (u32) current_stack_pointer();
*--isp = (u32) &regs;
*--isp = (u32) irq;

@@ -109,6 +109,24 @@ static char softirq_stack[NR_CPUS * THRE
static char hardirq_stack[NR_CPUS * THREAD_SIZE]
__attribute__((__aligned__(THREAD_SIZE)));

+
+unsigned long irq_previous_esp(struct thread_info *context)
+{
+ union irq_ctx *irqctx;
+
+ irqctx = hardirq_ctx[context->cpu];
+ if (&irqctx->tinfo == context)
+ goto ok;
+
+ irqctx = softirq_ctx[context->cpu];
+ if (&irqctx->tinfo == context)
+ goto ok;
+
+ return 0;
+ok:
+ return irqctx->stack[ARRAY_SIZE(irqctx->stack) - 1];
+}
+
/*
* allocate per-cpu stacks for hardirq and for softirq processing
*/
@@ -159,11 +177,12 @@ asmlinkage void do_softirq(void)
curctx = current_thread_info();
irqctx = softirq_ctx[smp_processor_id()];
irqctx->tinfo.task = curctx->task;
- irqctx->tinfo.previous_esp = current_stack_pointer();

/* build the stack frame on the softirq stack */
isp = (u32*) ((char*)irqctx + sizeof(*irqctx));

+ *--isp = (u32) current_stack_pointer();
+
asm volatile(
" xchgl %%ebx,%%esp \n"
" call __do_softirq \n"
diff -rup rc3-mm1-trace/arch/i386/kernel/traps.c rc3-mm1-noesp/arch/i386/kernel/traps.c
--- rc3-mm1-trace/arch/i386/kernel/traps.c 2004-10-04 10:55:03.000000000 +0400
+++ rc3-mm1-noesp/arch/i386/kernel/traps.c 2004-10-04 14:50:20.000000000 +0400
@@ -190,7 +190,7 @@ void show_trace(struct task_struct *task
context = (struct thread_info *)
((unsigned long)stack & (~(THREAD_SIZE - 1)));
ebp = print_context_stack(context, stack, ebp);
- stack = (unsigned long*)context->previous_esp;
+ stack = (unsigned long*)irq_previous_esp(context);
if (!stack)
break;
printk(" =======================\n");
diff -rup rc3-mm1-trace/include/asm-i386/irq.h rc3-mm1-noesp/include/asm-i386/irq.h
--- rc3-mm1-trace/include/asm-i386/irq.h 2004-10-04 10:26:41.000000000 +0400
+++ rc3-mm1-noesp/include/asm-i386/irq.h 2004-10-04 14:49:45.000000000 +0400
@@ -29,9 +29,14 @@ extern void release_vm86_irqs(struct tas

#ifdef CONFIG_4KSTACKS
extern void irq_ctx_init(int cpu);
+unsigned long irq_previous_esp(struct thread_info *context);
# define __ARCH_HAS_DO_SOFTIRQ
#else
# define irq_ctx_init(cpu) do { } while (0)
+static inline unsigned long irq_previous_esp(struct thread_info *context)
+{
+ return 0;
+}
#endif

#endif /* _ASM_IRQ_H */
diff -rup rc3-mm1-trace/include/asm-i386/thread_info.h rc3-mm1-noesp/include/asm-i386/thread_info.h
--- rc3-mm1-trace/include/asm-i386/thread_info.h 2004-09-13 09:31:43.000000000 +0400
+++ rc3-mm1-noesp/include/asm-i386/thread_info.h 2004-10-04 14:43:01.000000000 +0400
@@ -39,9 +39,6 @@ struct thread_info {
*/
struct restart_block restart_block;

- unsigned long previous_esp; /* ESP of the previous stack in case
- of nested (IRQ) stacks
- */
__u8 supervisor_stack[0];
};