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Date:   Thu, 10 Mar 2022 20:05:04 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     "H. Nikolaus Schaller" <hns@goldelico.com>
Cc:     Huang Pei <huangpei@loongson.cn>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Sasha Levin <sashal@kernel.org>,
        Christoph Hellwig <hch@lst.de>, stable@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@openphoenux.org>
Subject: Re: [BUG] new MIPS compile error on v5.15.27
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References: <D148EFBD-55E0-449A-AD2A-12C80ABD4FC4@goldelico.com>
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On Thu, Mar 10, 2022 at 05:25:07PM +0100, H. Nikolaus Schaller wrote:
> upstream commit 277c8cb3e8ac ("MIPS: fix local_{add,sub}_return on MIPS64")
> 
> was backported to v5.15.27 as
> 
> commit f98371d2ac83 ("MIPS: fix local_{add,sub}_return on MIPS64")
> 
> but breaks MIPS build:
> 
> In file included from ./arch/mips/include/asm/local.h:8:0,
>                  from ./include/linux/genhd.h:20,
>                  from ./include/linux/blkdev.h:8,
>                  from ./include/linux/blk-cgroup.h:23,
>                  from ./include/linux/writeback.h:14,
>                  from ./include/linux/memcontrol.h:22,
>                  from ./include/net/sock.h:53,
>                  from ./include/linux/tcp.h:19,
>                  from drivers/net/slip/slip.c:91:
> ./arch/mips/include/asm/asm.h:68:0: warning: "END" redefined
>  #define END(function)     \
>  
> In file included from drivers/net/slip/slip.c:88:0:
> drivers/net/slip/slip.h:44:0: note: this is the location of the previous definition
>  #define END             0300  /* indicates end of frame */
> 
> Analyses reveals that with the backported MIPS fix there is a new
> #include <asm/asm.h> introduced by ./arch/mips/include/asm/local.h
> which already defines some END macro.
> 
> But why does v5.16.x compile fine where
> 
> commit a0ecfd10d669c ("MIPS: fix local_{add,sub}_return on MIPS64")
> 
> is also present since v5.16.3?
> 
> Deeper analyses shows that there is another patch introduced
> in v5.16-rc1 which removed one #include in the above chain and
> therefore does not define END by asm/asm.h:
> 
> commit 348332e000697 ("mm: don't include <linux/blk-cgroup.h> in <linux/writeback.h>")
> 
> Hence, the MIPS fix should only be applied to branches where
> the mm fix is already present. Or the mm fix should be backported
> as well (if it has no side-effects).
> 
> Note: the MIPS fix was apparently not (yet?) applied to v5.10.y or earlier
> even tough the Fixes: 7232311ef14c ("local_t: mips extension")
> would be true.

Thanks for the report.  I'll work on resolving this for the next round
of stable releases _after_ the ones that are currently out for review
are released.

thanks,

greg k-h