linux-kernel - Re: [tip: locking/core] static_call: Fix function type mismatch

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Date:   Tue, 23 Mar 2021 08:37:33 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-tip-commits@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Ingo Molnar <mingo@...nel.org>, x86@...nel.org
Subject: Re: [tip: locking/core] static_call: Fix function type mismatch

On Mon, Mar 22, 2021 at 11:30:07PM -0000, tip-bot2 for Arnd Bergmann wrote:
> The following commit has been merged into the locking/core branch of tip:
> 
> Commit-ID:     335c73e7c8f7deb23537afbbbe4f8ab48bd5de52
> Gitweb:        https://git.kernel.org/tip/335c73e7c8f7deb23537afbbbe4f8ab48bd5de52
> Author:        Arnd Bergmann <arnd@...db.de>
> AuthorDate:    Mon, 22 Mar 2021 22:42:24 +01:00
> Committer:     Ingo Molnar <mingo@...nel.org>
> CommitterDate: Tue, 23 Mar 2021 00:08:53 +01:00
> 
> static_call: Fix function type mismatch
> 
> The __static_call_return0() function is declared to return a 'long',
> while it aliases a couple of functions that all return 'int'. When
> building with 'make W=1', gcc warns about this:
> 
>   kernel/sched/core.c:5420:37: error: cast between incompatible function types from 'long int (*)(void)' to 'int (*)(void)' [-Werror=cast-function-type]
>    5420 |   static_call_update(might_resched, (typeof(&__cond_resched)) __static_call_return0);
> 
> Change all these function to return 'long' as well, but remove the cast to
> ensure we get a warning if any of the types ever change.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Link: https://lore.kernel.org/r/20210322214309.730556-1-arnd@kernel.org

So I strongly disagree and think the warning is bad and should be
disabled. I'll go uncommit this patch.