25 Sep
2021
25 Sep
'21
12:08 p.m.
On Fri, Sep 24 2021 at 13:04, Thomas Gleixner wrote:
On Mon, Sep 13 2021 at 13:01, Sohil Mehta wrote:
+int uintr_receiver_wait(void) +{
- struct uintr_upid_ctx *upid_ctx;
- unsigned long flags;
- if (!is_uintr_receiver(current))
return -EOPNOTSUPP;- upid_ctx = current->thread.ui_recv->upid_ctx;
- upid_ctx->upid->nc.nv = UINTR_KERNEL_VECTOR;
- upid_ctx->waiting = true;
- spin_lock_irqsave(&uintr_wait_lock, flags);
- list_add(&upid_ctx->node, &uintr_wait_list);
- spin_unlock_irqrestore(&uintr_wait_lock, flags);
- set_current_state(TASK_INTERRUPTIBLE);
Because we have not enough properly implemented wait primitives you need to open code one which is blantantly wrong vs. a concurrent wake up?
- schedule();
How is that correct vs. a spurious wakeup? What takes care that the entry is removed from the list?
Again. We have proper wait primitives.
Aisde of that this is completely broken vs. CPU hotplug.
CPUX switchto(tsk) tsk->upid.ndst = apicid(smp_processor_id();
ret_to_user() ... sys_uintr_wait() ... schedule()
After that CPU X is unplugged which means the task won't be woken up by an user IPI which is issued after CPU X went down.
Thanks,
tglx