[PATCH RESEND] taskstats: remove unneeded dead assignment

[PATCH RESEND] taskstats: remove unneeded dead assignment

[Lukas Bulwahn]

make clang-analyzer on x86_64 defconfig caught my attention with:

  kernel/taskstats.c:120:2: warning: Value stored to 'rc' is never read \
  [clang-analyzer-deadcode.DeadStores]
          rc = 0;
          ^

Commit d94a041519f3 ("taskstats: free skb, avoid returns in
send_cpu_listeners") made send_cpu_listeners() not return a value and
hence, the rc variable remained only to be used within the loop where
it is always assigned before read and it does not need any other
initialisation.

So, simply remove this unneeded dead initializing assignment.

As compilers will detect this unneeded assignment and optimize this anyway,
the resulting object code is identical before and after this change.

No functional change. No change to object code.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
---
applies cleanly on current master and next-20201105
Resend: still applies cleanly on next-20211224

Balbir, please pick this minor non-urgent clean-up patch.

 kernel/taskstats.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index a2802b6ff4bb..bd18a7bf5276 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -117,7 +117,6 @@ static void send_cpu_listeners(struct sk_buff *skb,
 
 	genlmsg_end(skb, reply);
 
-	rc = 0;
 	down_read(&listeners->sem);
 	list_for_each_entry(s, &listeners->list, list) {
 		skb_next = NULL;
-- 
2.17.1

Re: [PATCH RESEND] taskstats: remove unneeded dead assignment

[Nick Desaulniers]

On Mon, Dec 27, 2021 at 5:10 AM Lukas Bulwahn <lukas.bulwahn@gmail.com> wrote:
>
> make clang-analyzer on x86_64 defconfig caught my attention with:
>
>   kernel/taskstats.c:120:2: warning: Value stored to 'rc' is never read \
>   [clang-analyzer-deadcode.DeadStores]
>           rc = 0;
>           ^
>
> Commit d94a041519f3 ("taskstats: free skb, avoid returns in
> send_cpu_listeners") made send_cpu_listeners() not return a value and
> hence, the rc variable remained only to be used within the loop where
> it is always assigned before read and it does not need any other
> initialisation.
>
> So, simply remove this unneeded dead initializing assignment.
>
> As compilers will detect this unneeded assignment and optimize this anyway,
> the resulting object code is identical before and after this change.
>
> No functional change. No change to object code.
>
> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>

I was going to ask "what happens when the list is empty?" but `rc` is
only used in a loop where that's not the case. Thanks for the patch!

It looks like
commit d94a041519f3 ("[PATCH] taskstats: free skb, avoid returns in
send_cpu_listeners")
from v2.6.18-rc4
is what changed send_cpu_listeners not to use rc outside of the loop.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
> applies cleanly on current master and next-20201105
> Resend: still applies cleanly on next-20211224
>
> Balbir, please pick this minor non-urgent clean-up patch.
>
>  kernel/taskstats.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/kernel/taskstats.c b/kernel/taskstats.c
> index a2802b6ff4bb..bd18a7bf5276 100644
> --- a/kernel/taskstats.c
> +++ b/kernel/taskstats.c
> @@ -117,7 +117,6 @@ static void send_cpu_listeners(struct sk_buff *skb,
>
>         genlmsg_end(skb, reply);
>
> -       rc = 0;
>         down_read(&listeners->sem);
>         list_for_each_entry(s, &listeners->list, list) {
>                 skb_next = NULL;
> --
> 2.17.1
>


-- 
Thanks,
~Nick Desaulniers