Re: next-20250825: arc: seqlock.h:876:2: error: implicit declaration of function 'spin_lock' [-Werror=implicit-function-declaration]

26 Aug 2025

      On 8/26/25 8:42 AM, Naresh Kamboju wrote:
...
On Tue, 26 Aug 2025 at 12:05, Naresh Kamboju naresh.kamboju@linaro.org wrote:
...
The following build warnings / errors noticed with arc defconfig with
gcc-9 toolchain.
Regression Analysis:

New regression? yes
Reproducibility? yes

Build regression: next-20250825 arc seqlock.h:876:2: error: implicit
declaration of function 'spin_lock'
[-Werror=implicit-function-declaration]
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
arc:
   build:
     * gcc-9-allnoconfig
     * gcc-9-tinyconfig
     * gcc-9-vdk_hs38_smp_defconfig
     * gcc-9-defconfig
     * gcc-9-axs103_defconfig
## Build log
In file included from include/linux/mmzone.h:17,
                  from include/linux/gfp.h:7,
                  from include/linux/mm.h:7,
                  from arch/arc/include/asm/arcregs.h:149,
                  from arch/arc/include/asm/irqflags-arcv2.h:9,
                  from arch/arc/include/asm/irqflags.h:13,
                  from include/linux/irqflags.h:18,
                  from include/linux/spinlock.h:59,
                  from include/linux/sched.h:37,
                  from arch/arc/kernel/asm-offsets.c:6:
include/linux/seqlock.h: In function 'write_seqlock':
include/linux/seqlock.h:876:2: error: implicit declaration of function
'spin_lock' [-Werror=implicit-function-declaration]
   876 |  spin_lock(&sl->lock);
       |  ^~~~~~~~~
include/linux/seqlock.h: In function 'write_sequnlock':
include/linux/seqlock.h:890:2: error: implicit declaration of function
'spin_unlock' [-Werror=implicit-function-declaration]
   890 |  spin_unlock(&sl->lock);
       |  ^~~~~~~~~~~
include/linux/seqlock.h: In function 'write_seqlock_bh':
include/linux/seqlock.h:902:2: error: implicit declaration of function
'spin_lock_bh' [-Werror=implicit-function-declaration]
   902 |  spin_lock_bh(&sl->lock);
       |  ^~~~~~~~~~~~
include/linux/seqlock.h: In function 'write_sequnlock_bh':
include/linux/seqlock.h:917:2: error: implicit declaration of function
'spin_unlock_bh' [-Werror=implicit-function-declaration]
   917 |  spin_unlock_bh(&sl->lock);
       |  ^~~~~~~~~~~~~~
include/linux/seqlock.h: In function 'write_seqlock_irq':
include/linux/seqlock.h:929:2: error: implicit declaration of function
'spin_lock_irq' [-Werror=implicit-function-declaration]
   929 |  spin_lock_irq(&sl->lock);
       |  ^~~~~~~~~~~~~
include/linux/seqlock.h: In function 'write_sequnlock_irq':
include/linux/seqlock.h:943:2: error: implicit declaration of function
'spin_unlock_irq'; did you mean 'write_sequnlock_irq'?
[-Werror=implicit-function-declaration]
   943 |  spin_unlock_irq(&sl->lock);
       |  ^~~~~~~~~~~~~~~
       |  write_sequnlock_irq
include/linux/seqlock.h: In function '__write_seqlock_irqsave':
include/linux/seqlock.h:950:2: error: implicit declaration of function
'spin_lock_irqsave' [-Werror=implicit-function-declaration]
   950 |  spin_lock_irqsave(&sl->lock, flags);
       |  ^~~~~~~~~~~~~~~~~
include/linux/seqlock.h: In function 'write_sequnlock_irqrestore':
include/linux/seqlock.h:981:2: error: implicit declaration of function
'spin_unlock_irqrestore'; did you mean 'write_sequnlock_irqrestore'?
[-Werror=implicit-function-declaration]
   981 |  spin_unlock_irqrestore(&sl->lock, flags);
       |  ^~~~~~~~~~~~~~~~~~~~~~
       |  write_sequnlock_irqrestore
In file included from include/linux/sched.h:15,
                  from arch/arc/kernel/asm-offsets.c:6:
include/linux/rcupdate.h: In function 'rcu_read_lock_sched_held':
include/linux/preempt.h:227:49: error: implicit declaration of
function 'irqs_disabled' [-Werror=implicit-function-declaration]
   227 | #define preemptible() (preempt_count() == 0 && !irqs_disabled())
       |                                                 ^~~~~~~~~~~~~
                           ^
cc1: some warnings being treated as errors
Anders bisected this and found,
  # first bad commit:
    [7cf258e5720ffdd5505faa04ab5afa9732ef0f6e]
    mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion-fix
The compilation problem is a result of bad include file ordering. Since 
the only users of PAGES_TO_MB() macro are kernel/rcu/rcuscale.c and 
mm/swap.c and they both include <linux/mm.h>. So this can be fixed by 
just removing the <linux/mm.h> include from arcregs.h.
Cheers,
Longman
...
...
## Source

Kernel version: 6.17.0-rc3-next-20250825
Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
Git describe: next-20250825
Git commit: 6c68f4c0a147c025ae0b25fab688c7c47964a02f
Architectures: arc
Toolchains: gcc-9
Kconfigs: defconfig

## Build

Build log: https://qa-reports.linaro.org/api/testruns/29652436/log_file/
Build details:

https://regressions.linaro.org/lkft/linux-next-master/next-20250825/build/gc...

Build error details:

https://regressions.linaro.org/lkft/linux-next-master/next-20250825/log-pars...

Build plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/builds/31lrYki7Mz...
Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/31lrYki7MzYyqtJKnutAe...
Kernel config:

https://storage.tuxsuite.com/public/linaro/lkft/builds/31lrYki7MzYyqtJKnutAe...
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https://lkft.linaro.org

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Re: next-20250825: arc: seqlock.h:876:2: error: implicit declaration of function 'spin_lock' [-Werror=implicit-function-declaration]