Re: [PATCH 07/18] sched/fair: Add push task mechanism for fair

[Shrikanth Hegde]

> > > +static int
> > > +select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags);
> > > +
> > > +/*
> > > + * See if the non running fair tasks on this rq can be sent on other CPUs
> > > + * that fits better with their profile.
> > > + */
> > > +static bool fair_push_task(struct rq *rq)
> > > +{
> > > +     struct task_struct *next_task;
> > > +     int prev_cpu, new_cpu;
> > > +     struct rq_flags rf;
> > > +     struct rq *cur_rq;
> >
> > You likely need below to keep clang's context tracking to be happy.
> >
> >          context_unsafe_alias(rq);
>
> I just noticed that I didn't answer to this one
>
> Why should I need this ?
>
> rq remains the same in fair_push_task(). I'm using rq and new_rq to
> differentiate both current and new rq
>
> >
I tried to use clang-23 and get below with the series applied.
It may not be exactly here. But somewhere.

make LLVM=/opt/llvm-23/bin/ \
        KCFLAGS="-Werror=thread-safety-analysis" \
        V=1 kernel/sched/fair.o

kernel/sched/fair.c:9971:2: error: releasing raw_spinlock 'rq_lockp(rq)' that was not held [-Werror,-Wthread-safety-analysis]
 9971 |         raw_spin_rq_unlock(rq);
      |         ^
kernel/sched/fair.c:9983:2: error: raw_spinlock 'rq_lockp(rq)' is not held on every path through here [-Werror,-Wthread-safety-analysis]
 9983 |         raw_spin_unlock(&next_task->pi_lock);
      |         ^
./include/linux/spinlock.h:279:32: note: expanded from macro 'raw_spin_unlock'
  279 | #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
      |                                         ^
kernel/sched/fair.c:9980:2: note: raw_spinlock acquired here
 9980 |         raw_spin_rq_lock(rq);
      |         ^
kernel/sched/fair.c:10085:2: error: releasing raw_spinlock 'rq_lockp(rq)' that was not held [-Werror,-Wthread-safety-analysis]
 10085 |         rq_unlock(rq, rf);
       |         ^
kernel/sched/fair.c:10093:1: error: raw_spinlock 'rq_lockp(rq)' is not held on every path through here
      [-Werror,-Wthread-safety-analysis]
 10093 | }
       | ^
kernel/sched/fair.c:10090:2: note: raw_spinlock acquired here
 10090 |         rq_lock(rq, rf);
       |         ^