Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls

Peter Zijlstra
2021-11-26T22:09:44Z

On Fri, Nov 26, 2021 at 10:59:44PM +0100, Peter Zijlstra wrote:

> That seems to loose the freezable crud.. then again, since we're
> interruptible, that shouldn't matter. Lemme go do that.

---

--- a/kernel/sched/umcg.c
+++ b/kernel/sched/umcg.c
@@ -52,7 +52,7 @@ static int umcg_pin_pages(void)

server = umcg_get_task(server_tid);
if (!server)
- return -EINVAL;
+ return -ESRCH;

if (pin_user_pages_fast((unsigned long)self, 1, 0,
&tsk->umcg_worker_page) != 1)
@@ -358,18 +358,10 @@ int umcg_wait(u64 timo)
{
struct task_struct *tsk = current;
struct umcg_task __user *self = tsk->umcg_task;
- struct hrtimer_sleeper timeout;
struct page *page = NULL;
u32 state;
int ret;

- if (timo) {
- hrtimer_init_sleeper_on_stack(&timeout, tsk->umcg_clock,
- HRTIMER_MODE_ABS);
- hrtimer_set_expires_range_ns(&timeout.timer, (s64)timo,
- tsk->timer_slack_ns);
- }
-
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);

@@ -415,22 +407,16 @@ int umcg_wait(u64 timo)
break;
}

- if (timo)
- hrtimer_sleeper_start_expires(&timeout, HRTIMER_MODE_ABS);
-
- freezable_schedule();
-
- ret = -ETIMEDOUT;
- if (timo && !timeout.task)
+ if (!schedule_hrtimeout_range_clock(timo ? &timo : NULL,
+ tsk->timer_slack_ns,
+ HRTIMER_MODE_ABS,
+ tsk->umcg_clock)) {
+ ret = -ETIMEDOUT;
break;
+ }
}
__set_current_state(TASK_RUNNING);

- if (timo) {
- hrtimer_cancel(&timeout.timer);
- destroy_hrtimer_on_stack(&timeout.timer);
- }
-
return ret;
}

@@ -515,7 +501,8 @@ void umcg_notify_resume(struct pt_regs *
goto done;

if (state & UMCG_TF_PREEMPT) {
- umcg_pin_pages();
+ if (umcg_pin_pages())
+ goto die;

if (umcg_update_state(tsk, UMCG_TASK_RUNNING,
UMCG_TASK_RUNNABLE, &next_tid))
@@ -586,7 +573,9 @@ SYSCALL_DEFINE2(umcg_wait, u32, flags, u
tsk->flags &= ~PF_UMCG_WORKER;

/* see umcg_sys_{enter,exit}() */
- umcg_pin_pages();
+ ret = umcg_pin_pages();
+ if (ret)
+ return ret;

ret = umcg_update_state(tsk, UMCG_TASK_RUNNING, UMCG_TASK_RUNNABLE, &next_tid);
if (ret)