On Thu, Nov 03, 2022 at 04:03:43PM -0400, Mathieu Desnoyers wrote:
> +void sched_vcpu_exit_signals(struct task_struct *t)
> +{
> + struct mm_struct *mm = t->mm;
> + unsigned long flags;
> +
> + if (!mm)
> + return;
> + local_irq_save(flags);
> + mm_vcpu_put(mm, t->mm_vcpu);
> + t->mm_vcpu = -1;
> + t->mm_vcpu_active = 0;
> + local_irq_restore(flags);
> +}
> +
> +void sched_vcpu_before_execve(struct task_struct *t)
> +{
> + struct mm_struct *mm = t->mm;
> + unsigned long flags;
> +
> + if (!mm)
> + return;
> + local_irq_save(flags);
> + mm_vcpu_put(mm, t->mm_vcpu);
> + t->mm_vcpu = -1;
> + t->mm_vcpu_active = 0;
> + local_irq_restore(flags);
> +}
> +
> +void sched_vcpu_after_execve(struct task_struct *t)
> +{
> + struct mm_struct *mm = t->mm;
> + unsigned long flags;
> +
> + WARN_ON_ONCE((t->flags & PF_KTHREAD) || !t->mm);
> +
> + local_irq_save(flags);
> + t->mm_vcpu = mm_vcpu_get(mm);
> + t->mm_vcpu_active = 1;
> + local_irq_restore(flags);
> + rseq_set_notify_resume(t);
> +}
> +static inline void mm_vcpu_put(struct mm_struct *mm, int vcpu)
> +{
> + lockdep_assert_irqs_disabled();
> + if (vcpu < 0)
> + return;
> + spin_lock(&mm->vcpu_lock);
> + __cpumask_clear_cpu(vcpu, mm_vcpumask(mm));
> + spin_unlock(&mm->vcpu_lock);
> +}
> +
> +static inline int mm_vcpu_get(struct mm_struct *mm)
> +{
> + int ret;
> +
> + lockdep_assert_irqs_disabled();
> + spin_lock(&mm->vcpu_lock);
> + ret = __mm_vcpu_get(mm);
> + spin_unlock(&mm->vcpu_lock);
> + return ret;
> +}
This:
local_irq_disable()
spin_lock()
thing is a PREEMPT_RT anti-pattern.
At the very very least this should then be raw_spin_lock(), not in the
least because you're calling this from under rq->lock, which itself is a
raw_spin_lock_t.
