Subject: Re: [PATCH] powerpc: Fix MAX_STACK_TRACE_ENTRIES too low warning again

From: Li Zhong <[email-masked]>
Date: Tue, 07 May 2013 16:29:24 +0800

On Tue, 2013-05-07 at 10:32 +0800, Li Zhong wrote:
> Saw this warning again, and this time from the ret_from_fork path. 
> 
> It seems we could clear the back chain earlier in copy_thread(), which
> could cover both path, and also fix potential lockdep usage in
> schedule_tail(), or exception occurred before we clear the back chain.

Sorry, I made some mistake, please ignore this patch...
It seems clearing the back chain shouldn't use kregs->gpr[1] below, it
should be ((unsigned long*)sp)[0]. I'll send an updated version.

Thanks, Zhong

> 
> Signed-off-by: Li Zhong <[email-masked]>
> ---
>  arch/powerpc/kernel/entry_32.S |    2 --
>  arch/powerpc/kernel/entry_64.S |    2 --
>  arch/powerpc/kernel/process.c  |    1 +
>  3 files changed, 1 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index e514de5..d22e73e 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -439,8 +439,6 @@ ret_from_fork:
>  ret_from_kernel_thread:
>  	REST_NVGPRS(r1)
>  	bl	schedule_tail
> -	li	r3,0
> -	stw	r3,0(r1)
>  	mtlr	r14
>  	mr	r3,r15
>  	PPC440EP_ERR42
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 3fe5259..48e8a86 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -376,8 +376,6 @@ _GLOBAL(ret_from_fork)
>  _GLOBAL(ret_from_kernel_thread)
>  	bl	.schedule_tail
>  	REST_NVGPRS(r1)
> -	li	r3,0
> -	std	r3,0(r1)
>  	ld	r14, 0(r14)
>  	mtlr	r14
>  	mr	r3,r15
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index ceb4e7b..2c9fc5e 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -973,6 +973,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
>  	 */
>  	sp -= sizeof(struct pt_regs);
>  	kregs = (struct pt_regs *) sp;
> +	kregs->gpr[1] = 0;
>  	sp -= STACK_FRAME_OVERHEAD;
>  	p->thread.ksp = sp;
>  	p->thread.ksp_limit = (unsigned long)task_stack_page(p) +