linux-kernel - Re: nolibc patches, still possible for 6.5 ?

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Message-Id: <20230608081337.7546-1-falcon@tinylab.org>
Date:   Thu,  8 Jun 2023 16:13:37 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     w@....eu
Cc:     falcon@...ylab.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, paulmck@...nel.org,
        thomas@...ch.de
Subject: Re: nolibc patches, still possible for 6.5 ?

Hi, Willy

> Hello Paul,
> 
> On Sun, Jun 04, 2023 at 03:57:54PM -0700, Paul E. McKenney wrote:
> > On Sun, Jun 04, 2023 at 03:20:11PM +0200, Willy Tarreau wrote:
> > > Hello Paul,
> > > 
> > > Thomas and Zhangjin have provided significant nolibc cleanups, and
> > > fixes, as well as preparation work to later support riscv32.
> > > 
> (...)
> > 
> > Given that the testing converges by the end of this week, I can't see
> > any reason why these cannot make v6.5.  (There were some kernel test
> > robot complaints as well, valid or not I am not sure.)
> 
> After Thomas' and Zhangjin's reviews and checks, I could run a mostly
> complete check:
>   - arm64, i386, x86_64 show 100% success
>   - arm, mips: 100% success, stackprotector skipped
>   - s390x, riscv64: run-user OK, kernel build fails (see below)
>   - loongarch: build OK, just not executed (need to upgrade my qemu
>     and I hate doing it late when some tests results are needed)
> 
> Regarding the build failure affecting s390x and riscv64, it's a regular
> kernel resulting from "make defconfig". For both archs, I'm getting this
> failure:
> 
>   In file included from kernel/rcu/update.c:649:
>   kernel/rcu/tasks.h: In function 'get_rcu_tasks_gp_kthread':
>     CC      fs/kernfs/dir.o
>     CC      security/bpf/hooks.o
>   kernel/rcu/tasks.h:1939:16: error: 'rcu_tasks' undeclared (first use in this function)
>    1939 |         return rcu_tasks.kthread_ptr;
>         |                ^~~~~~~~~
>   kernel/rcu/tasks.h:1939:16: note: each undeclared identifier is reported only once for each function it appears in
>   kernel/rcu/tasks.h:1940:1: error: control reaches end of non-void function [-Werror=return-type]
>    1940 | }
>         | ^
>   cc1: some warnings being treated as errors
> 
> I rebased the branch on top of 6.4-rc5 and got the same. I'm building
> with gcc-11.3.0 from kernel.org. I'm not sure whether this comes from
> my build environment or recent changes to the kernel, but I'm sure I
> haven't seen that error during 6.3-rc cycle. However, given that
> Zhangjin seems to have successfully built it for riscv, there might
> be something odd on my side.
>

Sorry, The reason is that to speed up the kernel build+nolibc tests, a
local small config was customized for the first report, it may not
trigger the above issue, in the later report about the v4 rv32 compile
support [1], I did test 'run' target with the default defconfig and
reported the same failure as bove, this is the note I pasted there:

  ---
  Did compile test for aarch64, rv32 and rv64, include run-user and run.

  Note, this is required with the default config from the
  20230606-nolibc-rv32+stkp7a branch of [5]:

    diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
    index ce02bb09651b..72bd8fe0cad6 100644
    --- a/kernel/rcu/tasks.h
    +++ b/kernel/rcu/tasks.h
    @@ -1934,11 +1934,13 @@ void show_rcu_tasks_gp_kthreads(void)
     }
     #endif /* #ifndef CONFIG_TINY_RCU */

    +#ifdef CONFIG_TASKS_RCU
     struct task_struct *get_rcu_tasks_gp_kthread(void)
     {
            return rcu_tasks.kthread_ptr;
     }
     EXPORT_SYMBOL_GPL(get_rcu_tasks_gp_kthread);
    +#endif

     #ifdef CONFIG_PROVE_RCU
     struct rcu_tasks_test_desc {
  ---

I have seen Paul have known the cause of the above issue in your later
discussion and you found a better solution to avoid such failures,
congrats!

[1]: https://lore.kernel.org/linux-riscv/cover.1686128703.git.falcon@tinylab.org/T/#t

Best regards,
Zhangjin

> Given that this build issue is not dependent on the selftest, I'm fine
> with the branch getting merged as-is, and can provide feedback on this
> build error if needed:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/wtarreau/nolibc.git 20230606-nolibc-rv32+stkp7a
> 
> Just let me know if you prefer that I resend the whole series or need
> more info etc, as usual.
> 
> Thank you!
> Willy