linux-kernel - Re: [linux-safety] [PATCH] taskstats: remove unneeded dead assignment

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Date:   Fri, 6 Nov 2020 10:25:30 +0000
From:   Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
To:     Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Balbir Singh <bsingharora@...il.com>
Cc:     Tom Rix <trix@...hat.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        kernel-janitors@...r.kernel.org, linux-safety@...ts.elisa.tech,
        linux-kernel@...r.kernel.org
Subject: Re: [linux-safety] [PATCH] taskstats: remove unneeded dead assignment

Hi Lukas,

On 06/11/2020 06:22, Lukas Bulwahn 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.

Might be better to remove 'rc' completely as it is only used for the if
condition now.

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index a2802b6ff4bb..63541f1ae04a 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -113,11 +113,10 @@ static void send_cpu_listeners(struct sk_buff *skb,
        struct listener *s, *tmp;
        struct sk_buff *skb_next, *skb_cur = skb;
        void *reply = genlmsg_data(genlhdr);
-       int rc, delcount = 0;
+       int delcount = 0;

        genlmsg_end(skb, reply);

-       rc = 0;
        down_read(&listeners->sem);
        list_for_each_entry(s, &listeners->list, list) {
                skb_next = NULL;
@@ -126,8 +125,8 @@ static void send_cpu_listeners(struct sk_buff *skb,
                        if (!skb_next)
                                break;
                }
-               rc = genlmsg_unicast(&init_net, skb_cur, s->pid);
-               if (rc == -ECONNREFUSED) {
+               if (genlmsg_unicast(&init_net, skb_cur, s->pid) ==
+                   -ECONNREFUSED) {
                        s->valid = 0;
                        delcount++;
                }




-- 
Regards
Sudip