[PATCH 1/2] x86: 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 --- 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 d3460af3d27a..0405cab6634d 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 2cd562f96c1f..1e393d27d701 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); -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 1/2] x86: 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 --- 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 d3460af3d27a..0405cab6634d 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 2cd562f96c1f..1e393d27d701 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); -- 2.1.0 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
