Since commit c02433dd6de3 ("arm64: split thread_info from task stack"),
CONFIG_THREAD_INFO_IN_TASK is enabled unconditionally for arm64. So
remove this always-true assertion from arch_dup_task_struct.
Signed-off-by: Dawei Li <[email protected]>
---
arch/arm64/kernel/process.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 7387b68c745b..4ae31b7af6c3 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -290,9 +290,6 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
fpsimd_preserve_current_state();
*dst = *src;
- /* We rely on the above assignment to initialize dst's thread_flags: */
- BUILD_BUG_ON(!IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK));
-
/*
* Detach src's sve_state (if any) from dst so that it does not
* get erroneously used or freed prematurely. dst's copies
--
2.27.0
On Fri, Feb 02, 2024 at 12:02:11PM +0800, Dawei Li wrote:
> Since commit c02433dd6de3 ("arm64: split thread_info from task stack"),
> CONFIG_THREAD_INFO_IN_TASK is enabled unconditionally for arm64. So
> remove this always-true assertion from arch_dup_task_struct.
>
> Signed-off-by: Dawei Li <[email protected]>
> ---
> arch/arm64/kernel/process.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 7387b68c745b..4ae31b7af6c3 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -290,9 +290,6 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
> fpsimd_preserve_current_state();
> *dst = *src;
>
> - /* We rely on the above assignment to initialize dst's thread_flags: */
> - BUILD_BUG_ON(!IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK));
> -
Does the above cause any problem today, or is this patch just a cleanup?
For the benefit of other reviewers, the assertion and comment were added in
commit:
4585fc59c0e8 ("arm64/sve: Fix wrong free for task->thread.sve_state")
.. back in 2019, 3 years after commit:
c02433dd6de3 ("arm64: split thread_info from task stack")
The comment and assertion were a safety-net for backports, since commit
4585fc59c0e8 was a fix which dependend upon the thread_info being contained
within task_struct, and couldn't be backported to kernels without
CONFIG_THREAD_INFO_IN_TASK.
I'm sure that we currently have plenty of other code with a similar (but
undocumented) dependency. Given we've unconditionally selected
CONFIG_THREAD_INFO_IN_TASK since v4.10, and the oldest longterm stable kernel
is v4.19 (with v4.14 having EOL'd last month), I think it makes sense to delete
the assertion and comment.
So FWIW:
Acked-by: Mark Rutland <[email protected]>
Mark.
Hi Mark,
Thanks for reviewing.
On Mon, Feb 05, 2024 at 12:06:18PM +0000, Mark Rutland wrote:
> On Fri, Feb 02, 2024 at 12:02:11PM +0800, Dawei Li wrote:
> > Since commit c02433dd6de3 ("arm64: split thread_info from task stack"),
> > CONFIG_THREAD_INFO_IN_TASK is enabled unconditionally for arm64. So
> > remove this always-true assertion from arch_dup_task_struct.
> >
> > Signed-off-by: Dawei Li <[email protected]>
> > ---
> > arch/arm64/kernel/process.c | 3 ---
> > 1 file changed, 3 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> > index 7387b68c745b..4ae31b7af6c3 100644
> > --- a/arch/arm64/kernel/process.c
> > +++ b/arch/arm64/kernel/process.c
> > @@ -290,9 +290,6 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
> > fpsimd_preserve_current_state();
> > *dst = *src;
> >
> > - /* We rely on the above assignment to initialize dst's thread_flags: */
> > - BUILD_BUG_ON(!IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK));
> > -
>
> Does the above cause any problem today, or is this patch just a cleanup?
It's just a cleanup patch.
>
> For the benefit of other reviewers, the assertion and comment were added in
> commit:
>
> 4585fc59c0e8 ("arm64/sve: Fix wrong free for task->thread.sve_state")
>
> .. back in 2019, 3 years after commit:
>
> c02433dd6de3 ("arm64: split thread_info from task stack")
>
> The comment and assertion were a safety-net for backports, since commit
> 4585fc59c0e8 was a fix which dependend upon the thread_info being contained
> within task_struct, and couldn't be backported to kernels without
> CONFIG_THREAD_INFO_IN_TASK.
Thanks for the update! It helps.
>
> I'm sure that we currently have plenty of other code with a similar (but
> undocumented) dependency. Given we've unconditionally selected
Totally agreed.
> CONFIG_THREAD_INFO_IN_TASK since v4.10, and the oldest longterm stable kernel
> is v4.19 (with v4.14 having EOL'd last month), I think it makes sense to delete
> the assertion and comment.
>
> So FWIW:
>
> Acked-by: Mark Rutland <[email protected]>
>
> Mark.
>
Thanks,
Dawei
Hi,
On Fri, Feb 02, 2024 at 12:02:11PM +0800, Dawei Li wrote:
> Since commit c02433dd6de3 ("arm64: split thread_info from task stack"),
> CONFIG_THREAD_INFO_IN_TASK is enabled unconditionally for arm64. So
> remove this always-true assertion from arch_dup_task_struct.
>
> Signed-off-by: Dawei Li <[email protected]>
Just a gentle remainder:).
Thanks,
Dawei
> ---
> arch/arm64/kernel/process.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 7387b68c745b..4ae31b7af6c3 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -290,9 +290,6 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
> fpsimd_preserve_current_state();
> *dst = *src;
>
> - /* We rely on the above assignment to initialize dst's thread_flags: */
> - BUILD_BUG_ON(!IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK));
> -
> /*
> * Detach src's sve_state (if any) from dst so that it does not
> * get erroneously used or freed prematurely. dst's copies
> --
> 2.27.0
>
On Fri, 02 Feb 2024 12:02:11 +0800, Dawei Li wrote:
> Since commit c02433dd6de3 ("arm64: split thread_info from task stack"),
> CONFIG_THREAD_INFO_IN_TASK is enabled unconditionally for arm64. So
> remove this always-true assertion from arch_dup_task_struct.
>
>
Applied to arm64 (for-next/misc), thanks!
[1/1] arm64: remove unneeded BUILD_BUG_ON assertion
https://git.kernel.org/arm64/c/bce79b0c8097
--
Catalin