On Thu 2022-09-01 10:27:06, Zhen Lei wrote:
> The patch->mod is not a protected object of mutex_lock(&klp_mutex). Since
> it's in the error handling branch, it might not be helpful to reduce lock
> conflicts, but it can reduce some code size.
>
> Before:
> text data bss dec hex filename
> 10330 464 8 10802 2a32 kernel/livepatch/core.o
>
> After:
> text data bss dec hex filename
> 10307 464 8 10779 2a1b kernel/livepatch/core.o
Please, is this part of some longterm effort to reduce the size of
the kernel? Or is this just some random observation?
> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
> ---
> kernel/livepatch/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 42f7e716d56bf72..cb7abc821a50584 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -1041,9 +1041,9 @@ int klp_enable_patch(struct klp_patch *patch)
> mutex_lock(&klp_mutex);
>
> if (!klp_is_patch_compatible(patch)) {
> + mutex_unlock(&klp_mutex);
> pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
> patch->mod->name);
> - mutex_unlock(&klp_mutex);
I do not see how this change could reliably reduce the code size.
As Joe wrote, it looks like a random effect that is specific to a
particular compiler version, compilation options, and architecture.
I am against these kind of random microptimizations. It is just a call
for problems. If you move printk() outside of a lock, you need to make
sure that the information is not racy.
It might be safe in this particular case. But it is a bad practice.
It adds an extra work. It is error-prone with questionable gain.
I am sorry but I NACK this patch. There must be better ways to
reduce the kernel binary size.
Best Regards,
Petr
