[PATCH v1 1/1] sched/fair: Mark cfs_bandwidth_used() and m*_vruntime() with __maybe_unused

[PATCH v1 1/1] sched/fair: Mark cfs_bandwidth_used() and m*_vruntime() with __maybe_unused

[Andy Shevchenko]

When cfs_bandwidth_used() is unused, it prevents kernel builds
with clang, `make W=1` and CONFIG_WERROR=y:

kernel/sched/fair.c:526:19: error: unused function 'max_vruntime' [-Werror,-Wunused-function]
  526 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
      |                   ^~~~~~~~~~~~
kernel/sched/fair.c:6580:20: error: unused function 'cfs_bandwidth_used' [-Werror,-Wunused-function]
 6580 | static inline bool cfs_bandwidth_used(void)
      |                    ^~~~~~~~~~~~~~~~~~

Fix this by marking them with __maybe_unused (all cases for the sake of
symmetry).

See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 kernel/sched/fair.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9057584ec06d..b9d35675db50 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -523,7 +523,7 @@ void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
  * Scheduling class tree data structure manipulation methods:
  */
 
-static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
+static inline __maybe_unused u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 {
 	s64 delta = (s64)(vruntime - max_vruntime);
 	if (delta > 0)
@@ -532,7 +532,7 @@ static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 	return max_vruntime;
 }
 
-static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
+static inline __maybe_unused u64 min_vruntime(u64 min_vruntime, u64 vruntime)
 {
 	s64 delta = (s64)(vruntime - min_vruntime);
 	if (delta < 0)
@@ -5547,7 +5547,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 #ifdef CONFIG_JUMP_LABEL
 static struct static_key __cfs_bandwidth_used;
 
-static inline bool cfs_bandwidth_used(void)
+static inline __maybe_unused bool cfs_bandwidth_used(void)
 {
 	return static_key_false(&__cfs_bandwidth_used);
 }
@@ -5562,7 +5562,7 @@ void cfs_bandwidth_usage_dec(void)
 	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
 }
 #else /* CONFIG_JUMP_LABEL */
-static bool cfs_bandwidth_used(void)
+static inline __maybe_unused bool cfs_bandwidth_used(void)
 {
 	return true;
 }
@@ -6577,7 +6577,7 @@ static void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p)
 
 #else /* CONFIG_CFS_BANDWIDTH */
 
-static inline bool cfs_bandwidth_used(void)
+static inline __maybe_unused bool cfs_bandwidth_used(void)
 {
 	return false;
 }
-- 
2.43.0.rc1.1336.g36b5255a03ac

Re: [PATCH v1 1/1] sched/fair: Mark cfs_bandwidth_used() and m*_vruntime() with __maybe_unused

[Andy Shevchenko]

On Thu, Sep 05, 2024 at 08:12:10PM +0300, Andy Shevchenko wrote:
> When cfs_bandwidth_used() is unused, it prevents kernel builds
> with clang, `make W=1` and CONFIG_WERROR=y:
> 
> kernel/sched/fair.c:526:19: error: unused function 'max_vruntime' [-Werror,-Wunused-function]
>   526 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
>       |                   ^~~~~~~~~~~~
> kernel/sched/fair.c:6580:20: error: unused function 'cfs_bandwidth_used' [-Werror,-Wunused-function]
>  6580 | static inline bool cfs_bandwidth_used(void)
>       |                    ^~~~~~~~~~~~~~~~~~
> 
> Fix this by marking them with __maybe_unused (all cases for the sake of
> symmetry).
> 
> See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static
> inline functions for W=1 build").

Any comments on this? Can it be eventually applied, please?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 1/1] sched/fair: Mark cfs_bandwidth_used() and m*_vruntime() with __maybe_unused

[Valentin Schneider]

On 05/09/24 20:12, Andy Shevchenko wrote:
> When cfs_bandwidth_used() is unused, it prevents kernel builds
> with clang, `make W=1` and CONFIG_WERROR=y:
>
> kernel/sched/fair.c:526:19: error: unused function 'max_vruntime' [-Werror,-Wunused-function]
>   526 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
>       |                   ^~~~~~~~~~~~
> kernel/sched/fair.c:6580:20: error: unused function 'cfs_bandwidth_used' [-Werror,-Wunused-function]
>  6580 | static inline bool cfs_bandwidth_used(void)
>       |                    ^~~~~~~~~~~~~~~~~~
>
> Fix this by marking them with __maybe_unused (all cases for the sake of
> symmetry).
>

I assume that's with CONFIG_CFS_BANDWIDTH=n? Looks like
cfs_bandwidth_used() uses are tucked away under helpers that themselves
only really do something for CONFIG_CFS_BANDWIDTH=y, so you could remove
the CONFIG_CFS_BANDWIDTH=n definition of cfs_bandwidth_used() directly.

This compiles:
---
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2d16c8545c71e..57abb4ae8af39 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5373,8 +5373,6 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq);
 
-static inline bool cfs_bandwidth_used(void);
-
 static void
 requeue_delayed_entity(struct sched_entity *se);
 
@@ -6754,11 +6752,6 @@ static void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p)
 
 #else /* CONFIG_CFS_BANDWIDTH */
 
-static inline bool cfs_bandwidth_used(void)
-{
-	return false;
-}
-
 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}

Re: [PATCH v1 1/1] sched/fair: Mark cfs_bandwidth_used() and m*_vruntime() with __maybe_unused

[Andy Shevchenko]

On Tue, Nov 12, 2024 at 12:48:42PM +0100, Valentin Schneider wrote:
> On 05/09/24 20:12, Andy Shevchenko wrote:
> > When cfs_bandwidth_used() is unused, it prevents kernel builds
> > with clang, `make W=1` and CONFIG_WERROR=y:
> >
> > kernel/sched/fair.c:526:19: error: unused function 'max_vruntime' [-Werror,-Wunused-function]
> >   526 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
> >       |                   ^~~~~~~~~~~~
> > kernel/sched/fair.c:6580:20: error: unused function 'cfs_bandwidth_used' [-Werror,-Wunused-function]
> >  6580 | static inline bool cfs_bandwidth_used(void)
> >       |                    ^~~~~~~~~~~~~~~~~~
> >
> > Fix this by marking them with __maybe_unused (all cases for the sake of
> > symmetry).
> >
> 
> I assume that's with CONFIG_CFS_BANDWIDTH=n? Looks like
> cfs_bandwidth_used() uses are tucked away under helpers that themselves
> only really do something for CONFIG_CFS_BANDWIDTH=y, so you could remove
> the CONFIG_CFS_BANDWIDTH=n definition of cfs_bandwidth_used() directly.

Thanks for looking into this!

> This compiles:

okay, consider then my patch as a report. Can you submit your version as you
seems much more familiar with this code than me?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 1/1] sched/fair: Mark cfs_bandwidth_used() and m*_vruntime() with __maybe_unused

[Valentin Schneider]

On 12/11/24 17:18, Andy Shevchenko wrote:
> On Tue, Nov 12, 2024 at 12:48:42PM +0100, Valentin Schneider wrote:
>> On 05/09/24 20:12, Andy Shevchenko wrote:
>> > When cfs_bandwidth_used() is unused, it prevents kernel builds
>> > with clang, `make W=1` and CONFIG_WERROR=y:
>> >
>> > kernel/sched/fair.c:526:19: error: unused function 'max_vruntime' [-Werror,-Wunused-function]
>> >   526 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
>> >       |                   ^~~~~~~~~~~~
>> > kernel/sched/fair.c:6580:20: error: unused function 'cfs_bandwidth_used' [-Werror,-Wunused-function]
>> >  6580 | static inline bool cfs_bandwidth_used(void)
>> >       |                    ^~~~~~~~~~~~~~~~~~
>> >
>> > Fix this by marking them with __maybe_unused (all cases for the sake of
>> > symmetry).
>> >
>> 
>> I assume that's with CONFIG_CFS_BANDWIDTH=n? Looks like
>> cfs_bandwidth_used() uses are tucked away under helpers that themselves
>> only really do something for CONFIG_CFS_BANDWIDTH=y, so you could remove
>> the CONFIG_CFS_BANDWIDTH=n definition of cfs_bandwidth_used() directly.
>
> Thanks for looking into this!
>
>> This compiles:
>
> okay, consider then my patch as a report. Can you submit your version as you
> seems much more familiar with this code than me?

Sure, I'll add this to my todolist.