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Message-ID: <550475C9.8000107@gmail.com>
Date: Sat, 14 Mar 2015 19:54:17 +0200
From: Alex Dowad <alexinbeijing@...il.com>
To: linux-kernel@...r.kernel.org
CC: Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
Matt Fleming <matt.fleming@...el.com>,
"open list:IA64 (Itanium) PL..." <linux-ia64@...r.kernel.org>
Subject: Re: [PATCH 13/32] ia64: copy_thread(): rename 'user_stack_size' argument
to 'kthread_arg'
Sorry, this patch was in error. (I learned about the IA64-only clone2
syscall too late.)
Please disregard. Thanks! Alex Dowad
On 13/03/15 20:14, Alex Dowad wrote:
> 'user_stack_size' is very misleading, since the argument is never used for the
> size of the user stack. Rather, it is an argument which is passed to the main
> function executed by a newly forked kernel thread. Hence, rename it to
> 'kthread_arg'.
>
> When forking a new user thread, the kernel thread arg was (uselessly) added
> to the new user stack pointer. This "worked", since the kernel thread arg is
> always zero when forking a user thread, but it was obviously not intended.
>
> Signed-off-by: Alex Dowad <alexinbeijing@...il.com>
> ---
> arch/ia64/kernel/process.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
> index b515149..d4a78da 100644
> --- a/arch/ia64/kernel/process.c
> +++ b/arch/ia64/kernel/process.c
> @@ -300,7 +300,7 @@ ia64_load_extra (struct task_struct *task)
> }
>
> /*
> - * Copy the state of an ia-64 thread.
> + * Copy the architecture-specific state of an ia-64 thread.
> *
> * We get here through the following call chain:
> *
> @@ -332,7 +332,7 @@ ia64_load_extra (struct task_struct *task)
> */
> int
> copy_thread(unsigned long clone_flags,
> - unsigned long user_stack_base, unsigned long user_stack_size,
> + unsigned long user_stack_base, unsigned long kthread_arg,
> struct task_struct *p)
> {
> extern char ia64_ret_from_clone;
> @@ -376,13 +376,14 @@ copy_thread(unsigned long clone_flags,
> ia64_drop_fpu(p); /* don't pick up stale state from a CPU's fph */
>
> if (unlikely(p->flags & PF_KTHREAD)) {
> + /* kernel thread */
> if (unlikely(!user_stack_base)) {
> /* fork_idle() called us */
> return 0;
> }
> memset(child_stack, 0, sizeof(*child_ptregs) + sizeof(*child_stack));
> child_stack->r4 = user_stack_base; /* payload */
> - child_stack->r5 = user_stack_size; /* argument */
> + child_stack->r5 = kthread_arg;
> /*
> * Preserve PSR bits, except for bits 32-34 and 37-45,
> * which we can't read.
> @@ -406,6 +407,8 @@ copy_thread(unsigned long clone_flags,
>
> return 0;
> }
> +
> + /* user thread */
> stack = ((struct switch_stack *) regs) - 1;
> /* copy parent's switch_stack & pt_regs to child: */
> memcpy(child_stack, stack, sizeof(*child_ptregs) + sizeof(*child_stack));
> @@ -416,7 +419,7 @@ copy_thread(unsigned long clone_flags,
> if (clone_flags & CLONE_SETTLS)
> child_ptregs->r13 = regs->r16; /* see sys_clone2() in entry.S */
> if (user_stack_base) {
> - child_ptregs->r12 = user_stack_base + user_stack_size - 16;
> + child_ptregs->r12 = user_stack_base - 16;
> child_ptregs->ar_bspstore = user_stack_base;
> child_ptregs->ar_rnat = 0;
> child_ptregs->loadrs = 0;
--
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