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x86/asm/entry: Delay loading sp0 slightly on task switch

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The change:

  75182b1632a8 ("x86/asm/entry: Switch all C consumers of kernel_stack to this_cpu_sp0()")

had the unintended side effect of changing the return value of
current_thread_info() during part of the context switch process.
Change it back.

This has no effect as far as I can tell -- it's just for
consistency.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/9fcaa47dd8487db59eed7a3911b6ae409476763e.1425692936.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-03-06 17:50:18 -08:00 committed by Ingo Molnar
parent 9b47668843
commit b27559a433
2 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/x86/kernel/process_32.c
View File

@ -255,11 +255,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
fpu = switch_fpu_prepare(prev_p, next_p, cpu);
/*
* Reload esp0.
*/
load_sp0(tss, next);
/*
* Save away %gs. No need to save %fs, as it was saved on the
* stack on entry. No need to save %es and %ds, as those are
@ -310,6 +305,11 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
*/
arch_end_context_switch(next_p);
/*
* Reload esp0. This changes current_thread_info().
*/
load_sp0(tss, next);
this_cpu_write(kernel_stack,
(unsigned long)task_stack_page(next_p) +
THREAD_SIZE - KERNEL_STACK_OFFSET);

6
arch/x86/kernel/process_64.c
View File

@ -283,9 +283,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
fpu = switch_fpu_prepare(prev_p, next_p, cpu);
/* Reload esp0 and ss1. */
load_sp0(tss, next);
/* We must save %fs and %gs before load_TLS() because
* %fs and %gs may be cleared by load_TLS().
*
@ -413,6 +410,9 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
/* Reload esp0 and ss1. This changes current_thread_info(). */
load_sp0(tss, next);
this_cpu_write(kernel_stack,
(unsigned long)task_stack_page(next_p) +
THREAD_SIZE - KERNEL_STACK_OFFSET);