Commit-ID: b27559a433bb6080d95c2593d4a2b81401197911
Gitweb: http://git.kernel.org/tip/b27559a433bb6080d95c2593d4a2b81401197911
Author: Andy Lutomirski <l...@amacapital.net>
AuthorDate: Fri, 6 Mar 2015 17:50:18 -0800
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Sat, 7 Mar 2015 09:34:03 +0100
x86/asm/entry: Delay loading sp0 slightly on task switch
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 <l...@amacapital.net>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Oleg Nesterov <o...@redhat.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Link:
http://lkml.kernel.org/r/9fcaa47dd8487db59eed7a3911b6ae409476763e.1425692936.git.l...@amacapital.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
arch/x86/kernel/process_32.c | 10 +++++-----
arch/x86/kernel/process_64.c | 6 +++---
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index d3460af..0405cab 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -256,11 +256,6 @@ __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
* always kernel segments while inside the kernel. Doing this
@@ -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);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 2cd562f..1e393d2 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -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);
--
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