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SubjectRe: [PATCH 4/5] x86/ftrace: Add annotations for ftrace_arch_code_modify_prepare() and ftrace_arch_code_modify_post_process()
On Mon,  1 Jun 2020 19:45:51 +0100
Jules Irenge <jbi.octave@gmail.com> wrote:

> Sparse reports warnings
>
> warning: context imbalance in ftrace_arch_code_modify_prepare()
> - wrong count at exit
> warning: context imbalance in ftrace_arch_code_modify_post_process()
> - wrong count at exit
>
> The root cause is that even if
> the annotations on the function are correct,
> mutex do not support annotation
> This makes Sparse to complain.
> To fix this,
> __acquire(&text_mutex) and
> __release(&text_mutex) annotations are added
> inside ftrace_arch_code_modify_prepare()
> and ftrace_arch_code_modify_post_process()
> respectively.

Wait what? This looks like either a bug in sparse, or we just remove the
annotations. This just makes the code ugly, and looks silly.

Nack!

-- Steve


>
> Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
> ---
> arch/x86/kernel/ftrace.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 37a0aeaf89e7..737c07ab2e07 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -46,6 +46,7 @@ int ftrace_arch_code_modify_prepare(void)
> * ftrace has it set to "read/write".
> */
> mutex_lock(&text_mutex);
> + __acquire(&text_mutex);
> ftrace_poke_late = 1;
> return 0;
> }
> @@ -61,6 +62,7 @@ int ftrace_arch_code_modify_post_process(void)
> text_poke_finish();
> ftrace_poke_late = 0;
> mutex_unlock(&text_mutex);
> + __release(&text_mutex);
> return 0;
> }
>

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