2020-07-12 13:43:10

by Guo Ren

Subject: [PATCH] riscv: Cleanup unnecessary define in asm-offset.c

From: Guo Ren <[email protected]>

- TASK_THREAD_SP is duplicated define
- TASK_STACK is no use at all
- Don't worry about thread_info's offset in task_struct, have
a look on comment in include/linux/sched.h:

struct task_struct {
/*
* For reasons of header soup (see current_thread_info()), this
* must be the first element of task_struct.
*/
struct thread_info thread_info;

Signed-off-by: Guo Ren <[email protected]>
---
arch/riscv/kernel/asm-offsets.c | 3 ---
arch/riscv/kernel/entry.S | 5 -----
2 files changed, 8 deletions(-)

diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index 07cb9c1..db20344 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -27,9 +27,6 @@ void asm_offsets(void)
OFFSET(TASK_THREAD_S9, task_struct, thread.s[9]);
OFFSET(TASK_THREAD_S10, task_struct, thread.s[10]);
OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]);
- OFFSET(TASK_THREAD_SP, task_struct, thread.sp);
- OFFSET(TASK_STACK, task_struct, stack);
- OFFSET(TASK_TI, task_struct, thread_info);
OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags);
OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count);
OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp);
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index cae7e6d..3e8707e 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -389,12 +389,7 @@ ENTRY(__switch_to)
lw a4, TASK_TI_CPU(a1)
sw a3, TASK_TI_CPU(a1)
sw a4, TASK_TI_CPU(a0)
-#if TASK_TI != 0
-#error "TASK_TI != 0: tp will contain a 'struct thread_info', not a 'struct task_struct' so get_current() won't work."
- addi tp, a1, TASK_TI
-#else
move tp, a1
-#endif
ret
ENDPROC(__switch_to)

--
2.7.4

2020-07-22 01:47:55

by Palmer Dabbelt

Subject: Re: [PATCH] riscv: Cleanup unnecessary define in asm-offset.c

On Sun, 12 Jul 2020 06:41:49 PDT (-0700), [email protected] wrote:
> From: Guo Ren <[email protected]>
>
> - TASK_THREAD_SP is duplicated define
> - TASK_STACK is no use at all
> - Don't worry about thread_info's offset in task_struct, have
> a look on comment in include/linux/sched.h:
>
> struct task_struct {
> /*
> * For reasons of header soup (see current_thread_info()), this
> * must be the first element of task_struct.
> */
> struct thread_info thread_info;
>
> Signed-off-by: Guo Ren <[email protected]>
> ---
> arch/riscv/kernel/asm-offsets.c | 3 ---
> arch/riscv/kernel/entry.S | 5 -----
> 2 files changed, 8 deletions(-)
>
> diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
> index 07cb9c1..db20344 100644
> --- a/arch/riscv/kernel/asm-offsets.c
> +++ b/arch/riscv/kernel/asm-offsets.c
> @@ -27,9 +27,6 @@ void asm_offsets(void)
> OFFSET(TASK_THREAD_S9, task_struct, thread.s[9]);
> OFFSET(TASK_THREAD_S10, task_struct, thread.s[10]);
> OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]);
> - OFFSET(TASK_THREAD_SP, task_struct, thread.sp);
> - OFFSET(TASK_STACK, task_struct, stack);
> - OFFSET(TASK_TI, task_struct, thread_info);
> OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags);
> OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count);
> OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp);
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index cae7e6d..3e8707e 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -389,12 +389,7 @@ ENTRY(__switch_to)
> lw a4, TASK_TI_CPU(a1)
> sw a3, TASK_TI_CPU(a1)
> sw a4, TASK_TI_CPU(a0)
> -#if TASK_TI != 0
> -#error "TASK_TI != 0: tp will contain a 'struct thread_info', not a 'struct task_struct' so get_current() won't work."
> - addi tp, a1, TASK_TI
> -#else
> move tp, a1
> -#endif

Seems reasonable. That was really there to save anyone who got bit by the
conversion to to THREAD_INFO_IN_TASK.

I've added a comment and put this on for-next.

Thanks!

> ret
> ENDPROC(__switch_to)

Reviewed-by: Palmer Dabbelt <[email protected]>