[PATCH bpf-next v3 0/2] selftests/bpf: Fix "expression result unused" warnings with icecc

[PATCH bpf-next v3 0/2] selftests/bpf: Fix "expression result unused" warnings with icecc

[Ilya Leoshkevich]

v2: https://lore.kernel.org/bpf/20250827130519.411700-1-iii@linux.ibm.com/
v2 -> v3: Do not touch libbpf, explain how having two function
          declarations works (Andrii).
          Fix bpf-gcc build (CI).

v1: https://lore.kernel.org/bpf/20250508113804.304665-1-iii@linux.ibm.com/
v1 -> v2: Annotate bpf_obj_new_impl() with __must_check (Alexei).
          Add an explanation about icecc.

Hi,

I took another look at the "expression result unused" warnings I've
been seeing, and it turned out that the root cause was the icecc
compiler wrapper and what I consider a clang bug. Back then I've
reported that the problem was reproducible with plain clang, but now
I see that it was clearly a mixup, sorry about that.

In this series I implement Alexei's suggestion to annotate
bpf_obj_new_impl() with __must_check and add (void) casts to the
respective testcase.

There remain two awkward (void) casts and I'm not sure if I can somehow
make them look nicer. But I've added a detailed explanation how they
are helpful to the commit message.

Best regards,
Ilya


Ilya Leoshkevich (2):
  selftests/bpf: Annotate bpf_obj_new_impl() with __must_check
  selftests/bpf: Fix "expression result unused" warnings with icecc

 .../testing/selftests/bpf/bpf_experimental.h  |  6 ++++-
 .../selftests/bpf/progs/bpf_arena_spin_lock.h |  4 ++--
 .../selftests/bpf/progs/linked_list_fail.c    | 23 +++++++++++++++----
 3 files changed, 26 insertions(+), 7 deletions(-)

-- 
2.50.1

[PATCH bpf-next v3 1/2] selftests/bpf: Annotate bpf_obj_new_impl() with __must_check

[Ilya Leoshkevich]

The verifier requires that pointers returned by bpf_obj_new_impl() are
either dropped or stored in a map. Therefore programs that do not use
its return values will fail to load. Make the compiler point out these
issues. Adjust selftests that check that the verifier does indeed spot
these bugs.

Note that now there two different bpf_obj_new_impl() declarations: one
with __must_check from bpf_experimental.h, and one without from
vmlinux.h. According to the GCC doc [1] this is fine and has the
desired effect:

    Compatible attribute specifications on distinct declarations of the
    same function are merged.

[1] https://gcc.gnu.org/onlinedocs/gcc-12.4.0/gcc/Function-Attributes.html

Link: https://lore.kernel.org/bpf/CAADnVQL6Q+QRv3_JwEd26biwGpFYcwD_=BjBJWLAtpgOP9CKRw@mail.gmail.com/
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 .../testing/selftests/bpf/bpf_experimental.h  |  6 ++++-
 .../selftests/bpf/progs/linked_list_fail.c    | 23 +++++++++++++++----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index da7e230f2781..a8f206f4fdb9 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -8,6 +8,10 @@
 
 #define __contains(name, node) __attribute__((btf_decl_tag("contains:" #name ":" #node)))
 
+#ifndef __must_check
+#define __must_check __attribute__((__warn_unused_result__))
+#endif
+
 /* Description
  *	Allocates an object of the type represented by 'local_type_id' in
  *	program BTF. User may use the bpf_core_type_id_local macro to pass the
@@ -20,7 +24,7 @@
  *	A pointer to an object of the type corresponding to the passed in
  *	'local_type_id', or NULL on failure.
  */
-extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
+extern __must_check void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
 
 /* Convenience macro to wrap over bpf_obj_new_impl */
 #define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))
diff --git a/tools/testing/selftests/bpf/progs/linked_list_fail.c b/tools/testing/selftests/bpf/progs/linked_list_fail.c
index 6438982b928b..1e30d103e1c7 100644
--- a/tools/testing/selftests/bpf/progs/linked_list_fail.c
+++ b/tools/testing/selftests/bpf/progs/linked_list_fail.c
@@ -212,22 +212,33 @@ int map_compat_raw_tp_w(void *ctx)
 SEC("?tc")
 int obj_type_id_oor(void *ctx)
 {
-	bpf_obj_new_impl(~0UL, NULL);
+	void *f;
+
+	f = bpf_obj_new_impl(~0UL, NULL);
+	(void)f;
+
 	return 0;
 }
 
 SEC("?tc")
 int obj_new_no_composite(void *ctx)
 {
-	bpf_obj_new_impl(bpf_core_type_id_local(int), (void *)42);
+	void *f;
+
+	f = bpf_obj_new_impl(bpf_core_type_id_local(int), (void *)42);
+	(void)f;
+
 	return 0;
 }
 
 SEC("?tc")
 int obj_new_no_struct(void *ctx)
 {
+	void *f;
+
+	f = bpf_obj_new(union { int data; unsigned udata; });
+	(void)f;
 
-	bpf_obj_new(union { int data; unsigned udata; });
 	return 0;
 }
 
@@ -252,7 +263,11 @@ int new_null_ret(void *ctx)
 SEC("?tc")
 int obj_new_acq(void *ctx)
 {
-	bpf_obj_new(struct foo);
+	void *f;
+
+	f = bpf_obj_new(struct foo);
+	(void)f;
+
 	return 0;
 }
 
-- 
2.50.1

Re: [PATCH bpf-next v3 1/2] selftests/bpf: Annotate bpf_obj_new_impl() with __must_check

[Yonghong Song]

On 8/27/25 12:46 PM, Ilya Leoshkevich wrote:
> The verifier requires that pointers returned by bpf_obj_new_impl() are
> either dropped or stored in a map. Therefore programs that do not use
> its return values will fail to load. Make the compiler point out these
> issues. Adjust selftests that check that the verifier does indeed spot
> these bugs.
>
> Note that now there two different bpf_obj_new_impl() declarations: one
> with __must_check from bpf_experimental.h, and one without from
> vmlinux.h. According to the GCC doc [1] this is fine and has the
> desired effect:
>
>      Compatible attribute specifications on distinct declarations of the
>      same function are merged.
>
> [1] https://gcc.gnu.org/onlinedocs/gcc-12.4.0/gcc/Function-Attributes.html
>
> Link: https://lore.kernel.org/bpf/CAADnVQL6Q+QRv3_JwEd26biwGpFYcwD_=BjBJWLAtpgOP9CKRw@mail.gmail.com/
> Suggested-by: Alexei Starovoitov <ast@kernel.org>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>   .../testing/selftests/bpf/bpf_experimental.h  |  6 ++++-
>   .../selftests/bpf/progs/linked_list_fail.c    | 23 +++++++++++++++----
>   2 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> index da7e230f2781..a8f206f4fdb9 100644
> --- a/tools/testing/selftests/bpf/bpf_experimental.h
> +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> @@ -8,6 +8,10 @@
>   
>   #define __contains(name, node) __attribute__((btf_decl_tag("contains:" #name ":" #node)))
>   
> +#ifndef __must_check
> +#define __must_check __attribute__((__warn_unused_result__))
> +#endif

As you mentioned in Patch 2, we definitely has an issue with clang. I tried the following
experiments with latest master branch.

$ cat run3.sh
echo ".c => .i => .o"

clang  -g -Wall -Werror -D__TARGET_ARCH_x86 -mlittle-endian \
   -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include \
   -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf \
   -I/home/yhs/work/bpf-next/tools/include/uapi \
   -I/home/yhs/work/bpf-next/tools/testing/selftests/usr/include \
   -std=gnu11 -fno-strict-aliasing -Wno-compare-distinct-pointer-types \
   -idirafter /home/yhs/work/llvm-project/llvm/build.21/Release/lib/clang/21/include \
   -idirafter /usr/local/include -idirafter /usr/include    -DENABLE_ATOMICS_TESTS \
   -O2 --target=bpfel -E progs/linked_list_fail.c -mcpu=v4 \
   -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/linked_list_fail.i
clang  -g -Wall -Werror -mlittle-endian -std=gnu11 -fno-strict-aliasing \
   -Wno-compare-distinct-pointer-types -O2 --target=bpfel -c linked_list_fail.i \
   -mcpu=v4 \
   -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/cpuv4/linked_list_fail.bpf.o

echo ".c => .o"

clang  -g -Wall -Werror -D__TARGET_ARCH_x86 -mlittle-endian \
   -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include \
   -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf \
   -I/home/yhs/work/bpf-next/tools/include/uapi \
   -I/home/yhs/work/bpf-next/tools/testing/selftests/usr/include \
   -std=gnu11 -fno-strict-aliasing -Wno-compare-distinct-pointer-types \
   -idirafter /home/yhs/work/llvm-project/llvm/build.21/Release/lib/clang/21/include \
   -idirafter /usr/local/include -idirafter /usr/include    -DENABLE_ATOMICS_TESTS \
   -O2 --target=bpfel -c progs/linked_list_fail.c -mcpu=v4 \
   -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/cpuv4/linked_list_fail.bpf.o
$ ./run3.sh
.c => .i => .o
progs/linked_list_fail.c:230:3: error: expression result unused [-Werror,-Wunused-value]
   230 |  ((union { int data; unsigned udata; } *)bpf_obj_new_impl(__builtin_btf_type_id(*((typeof(union { int data; unsigned udata; }) *) 0), BPF_TYPE_ID_LOCAL), ((void *)0)));
       |   ^                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
progs/linked_list_fail.c:255:3: error: expression result unused [-Werror,-Wunused-value]
   255 |  ((struct foo *)bpf_obj_new_impl(__builtin_btf_type_id(*((typeof(struct foo) *) 0), BPF_TYPE_ID_LOCAL), ((void *)0)));
       |   ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.
.c => .o
$

The clang compilation command line is from selftest build with V=1.

Compiling from .c to .o is okay, but from .c => .i => .o will have
errors due to unused value.

I think you do not need __must_check here. '-Wall -Werror' seems already covered this.
You can also mention the clang bug in the commit message. The fix will be below:

diff --git a/tools/testing/selftests/bpf/progs/linked_list_fail.c b/tools/testing/selftests/bpf/progs/linked_list_fail.c
index 6438982b928b..35616b5c9b9e 100644
--- a/tools/testing/selftests/bpf/progs/linked_list_fail.c
+++ b/tools/testing/selftests/bpf/progs/linked_list_fail.c
@@ -227,7 +227,7 @@ SEC("?tc")
  int obj_new_no_struct(void *ctx)
  {
  
-       bpf_obj_new(union { int data; unsigned udata; });
+       (void)bpf_obj_new(union { int data; unsigned udata; });
         return 0;
  }
  
@@ -252,7 +252,7 @@ int new_null_ret(void *ctx)
  SEC("?tc")
  int obj_new_acq(void *ctx)
  {
-       bpf_obj_new(struct foo);
+       (void)bpf_obj_new(struct foo);
         return 0;
  }

I think this probably will address your icecc issue.


> +
>   /* Description
>    *	Allocates an object of the type represented by 'local_type_id' in
>    *	program BTF. User may use the bpf_core_type_id_local macro to pass the
> @@ -20,7 +24,7 @@
>    *	A pointer to an object of the type corresponding to the passed in
>    *	'local_type_id', or NULL on failure.
>    */
> -extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
> +extern __must_check void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
>   
>   /* Convenience macro to wrap over bpf_obj_new_impl */
>   #define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))
> diff --git a/tools/testing/selftests/bpf/progs/linked_list_fail.c b/tools/testing/selftests/bpf/progs/linked_list_fail.c
> index 6438982b928b..1e30d103e1c7 100644
> --- a/tools/testing/selftests/bpf/progs/linked_list_fail.c
> +++ b/tools/testing/selftests/bpf/progs/linked_list_fail.c
> @@ -212,22 +212,33 @@ int map_compat_raw_tp_w(void *ctx)
>   SEC("?tc")
>   int obj_type_id_oor(void *ctx)
>   {
> -	bpf_obj_new_impl(~0UL, NULL);
> +	void *f;
> +
> +	f = bpf_obj_new_impl(~0UL, NULL);
> +	(void)f;
> +
>   	return 0;
>   }
>   
>   SEC("?tc")
>   int obj_new_no_composite(void *ctx)
>   {
> -	bpf_obj_new_impl(bpf_core_type_id_local(int), (void *)42);
> +	void *f;
> +
> +	f = bpf_obj_new_impl(bpf_core_type_id_local(int), (void *)42);
> +	(void)f;
> +
>   	return 0;
>   }
>   
>   SEC("?tc")
>   int obj_new_no_struct(void *ctx)
>   {
> +	void *f;
> +
> +	f = bpf_obj_new(union { int data; unsigned udata; });
> +	(void)f;
>   
> -	bpf_obj_new(union { int data; unsigned udata; });
>   	return 0;
>   }
>   
> @@ -252,7 +263,11 @@ int new_null_ret(void *ctx)
>   SEC("?tc")
>   int obj_new_acq(void *ctx)
>   {
> -	bpf_obj_new(struct foo);
> +	void *f;
> +
> +	f = bpf_obj_new(struct foo);
> +	(void)f;
> +
>   	return 0;
>   }
>   

Re: [PATCH bpf-next v3 1/2] selftests/bpf: Annotate bpf_obj_new_impl() with __must_check

[Alexei Starovoitov]

On Wed, Aug 27, 2025 at 2:38 PM Yonghong Song <yonghong.song@linux.dev> wrote:
>
>
> diff --git a/tools/testing/selftests/bpf/progs/linked_list_fail.c b/tools/testing/selftests/bpf/progs/linked_list_fail.c
> index 6438982b928b..35616b5c9b9e 100644
> --- a/tools/testing/selftests/bpf/progs/linked_list_fail.c
> +++ b/tools/testing/selftests/bpf/progs/linked_list_fail.c
> @@ -227,7 +227,7 @@ SEC("?tc")
>   int obj_new_no_struct(void *ctx)
>   {
>
> -       bpf_obj_new(union { int data; unsigned udata; });
> +       (void)bpf_obj_new(union { int data; unsigned udata; });
>          return 0;
>   }
>
> @@ -252,7 +252,7 @@ int new_null_ret(void *ctx)
>   SEC("?tc")
>   int obj_new_acq(void *ctx)
>   {
> -       bpf_obj_new(struct foo);
> +       (void)bpf_obj_new(struct foo);
>          return 0;
>   }
>
> I think this probably will address your icecc issue.

Ilya,

does above fix it ?

If so we should probably do that and hold on __must_check,
since if we're getting pedantic __alloc_size__ is a better tag
than __must_check, but it will be even harder to get through pahole.

[PATCH bpf-next v3 2/2] selftests/bpf: Fix "expression result unused" warnings with icecc

[Ilya Leoshkevich]

icecc is a compiler wrapper that distributes compile jobs over a build
farm [1]. It works by sending toolchain binaries and preprocessed
source code to remote machines.

Unfortunately using it with BPF selftests causes build failures due to
a clang bug [2]. The problem is that clang suppresses the
-Wunused-value warning if the unused expression comes from a macro
expansion. Since icecc compiles preprocessed source code, this
information is not available. This leads to -Wunused-value false
positives.

arena_spin_lock_slowpath() uses two macros that produce values and
ignores the results. Add (void) cast to explicitly indicate that this
is intentional and suppress the warning.

An alternative solution is to change the macros to not produce values.
This would work today, but in the future there may appear users who
need them. Another potential solution is to replace these macros with
functions. Unfortunately this would not work, because these macros
work with unknown types and control flow.

[1] https://github.com/icecc/icecream
[2] https://github.com/llvm/llvm-project/issues/142614

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h b/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h
index d67466c1ff77..f90531cf3ee5 100644
--- a/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h
+++ b/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h
@@ -302,7 +302,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
 	 * barriers.
 	 */
 	if (val & _Q_LOCKED_MASK)
-		smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
+		(void)smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
 
 	/*
 	 * take ownership and clear the pending bit.
@@ -380,7 +380,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
 		/* Link @node into the waitqueue. */
 		WRITE_ONCE(prev->next, node);
 
-		arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
+		(void)arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
 
 		/*
 		 * While waiting for the MCS lock, the next pointer may have
-- 
2.50.1

Re: [PATCH bpf-next v3 2/2] selftests/bpf: Fix "expression result unused" warnings with icecc

[Yonghong Song]

On 8/27/25 12:46 PM, Ilya Leoshkevich wrote:
> icecc is a compiler wrapper that distributes compile jobs over a build
> farm [1]. It works by sending toolchain binaries and preprocessed
> source code to remote machines.
>
> Unfortunately using it with BPF selftests causes build failures due to
> a clang bug [2]. The problem is that clang suppresses the
> -Wunused-value warning if the unused expression comes from a macro
> expansion. Since icecc compiles preprocessed source code, this
> information is not available. This leads to -Wunused-value false
> positives.
>
> arena_spin_lock_slowpath() uses two macros that produce values and
> ignores the results. Add (void) cast to explicitly indicate that this
> is intentional and suppress the warning.
>
> An alternative solution is to change the macros to not produce values.
> This would work today, but in the future there may appear users who
> need them. Another potential solution is to replace these macros with
> functions. Unfortunately this would not work, because these macros
> work with unknown types and control flow.
>
> [1] https://github.com/icecc/icecream
> [2] https://github.com/llvm/llvm-project/issues/142614

As you described in [1] and [2]. The failure is due to the compilation from .i file to .o file.

$ cat run2.sh
echo '.c -> .i -> .o'
clang  -g -Wall -Werror -D__TARGET_ARCH_x86 -mlittle-endian -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf -I/home/yhs/work/bpf-next/tools/include/uapi -I/home/yhs/work/bpf-next/tools/testing/selftests/usr/include -std=gnu11 -fno-strict-aliasing -Wno-compare-distinct-pointer-types -idirafter /home/yhs/work/llvm-project/llvm/build.21/Release/lib/clang/21/include -idirafter /usr/local/include -idirafter /usr/include    -DENABLE_ATOMICS_TESTS   -O2 --target=bpfel -E progs/arena_spin_lock.c -mcpu=v4 -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/arena_spin_lock.i
clang  -g -Wall -Werror -mlittle-endian -std=gnu11 -fno-strict-aliasing -Wno-compare-distinct-pointer-types -O2 --target=bpfel -c arena_spin_lock.i -mcpu=v4 -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/cpuv4/arena_spin_lock.bpf.o

echo '.c -> .o'
clang  -g -Wall -Werror -D__TARGET_ARCH_x86 -mlittle-endian -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf -I/home/yhs/work/bpf-next/tools/include/uapi -I/home/yhs/work/bpf-next/tools/testing/selftests/usr/include -std=gnu11 -fno-strict-aliasing -Wno-compare-distinct-pointer-types -idirafter /home/yhs/work/llvm-project/llvm/build.21/Release/lib/clang/21/include -idirafter /usr/local/include -idirafter /usr/include    -DENABLE_ATOMICS_TESTS   -O2 --target=bpfel -c progs/arena_spin_lock.c -mcpu=v4 -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/cpuv4/arena_spin_lock.bpf.o

$ ./run2.sh
.c -> .i -> .o
In file included from progs/arena_spin_lock.c:7:
progs/bpf_arena_spin_lock.h:305:1765: error: expression result unused [-Werror,-Wunused-value]
   305 |   ...unsigned long __val; __sync_fetch_and_add(&__val, 0); }); else asm volatile("" ::: "memory"); }); }); (typeof(*(&lock->locked)))__val; });
       |                                                                                                            ^                         ~~~~~
progs/bpf_arena_spin_lock.h:383:1769: error: expression result unused [-Werror,-Wunused-value]
   383 |   ...unsigned long __val; __sync_fetch_and_add(&__val, 0); }); else asm volatile("" ::: "memory"); }); }); (typeof(*(&node->locked)))__val; });
       |                                                                                                            ^                         ~~~~~
2 errors generated.
.c -> .o
$

I am not sure whether we should do anything with pahole or libbpf. Essentially this is a clang
bug. We should push clang community to fix the problem.

>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>   tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h b/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h
> index d67466c1ff77..f90531cf3ee5 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h
> +++ b/tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h
> @@ -302,7 +302,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
>   	 * barriers.
>   	 */
>   	if (val & _Q_LOCKED_MASK)
> -		smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
> +		(void)smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
>   
>   	/*
>   	 * take ownership and clear the pending bit.
> @@ -380,7 +380,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
>   		/* Link @node into the waitqueue. */
>   		WRITE_ONCE(prev->next, node);
>   
> -		arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
> +		(void)arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
>   
>   		/*
>   		 * While waiting for the MCS lock, the next pointer may have