interruptible_sleep_on_timeout replacement

Hello Arnd,

I have to port /ancient/ code to v4.1
The problematic line is:

  long timeout_jiffies = US_TO_JIFFIES(wait_param->timeout_microsecond);
  ...
  timeout_jiffies = interruptible_sleep_on_timeout(&(llad_context.irq_queue), timeout_jiffies);
  wait_param->timeout_microsecond = JIFFIES_TO_US(timeout_jiffies);

IIUC, the appropriate replacement is

wait_event_interruptible_timeout(wq, condition, timeout)

where wq and timeout are the original parameters?

To determine the condition... do I have to examine the corresponding wake_up_interruptible() calls? I do see several

	if (status & SOME_VAL) {
		if (!test_and_set_bit(LOG2_SOME_VAL, &(llad_context.irq_bits)))
			wake_up_interruptible(&(llad_context.irq_queue));
	}

Also I'm not sure the return value is a direct match?

Regards.

Right, so it's most probably buggy (anything using *_sleep_on* is buggy almost by definition.)

wait_event_interruptible_timeout is documented very well in include/linux/wait.h.

Quoting random bits of out of context code really doesn't help anyone, especially with something this complex. We really need to see the whole driver to comment properly.

Condition is, as the documentation says, is the condition to be waited for, which should evaluate to true to terminate the wait prior to the timeout.

It doesn't. You're expected to know how much longer you need to wait. So, you need something like:

I think you will want something like this:

	long timeout_jiffies = US_TO_JIFFIES(wait_param->timeout_microsecond);
	long target_jiffies = jiffies + timeout_jiffies;
	long ret;
	...

	ret = wait_event_interruptible_timeout(&llad_context.irq_queue,
					       ... some condition ...
					       timeout_jiffies);

	if (ret < 0) {
		long now = jiffies;

		if (time_before_eq(now, target_jiffies))
			wait_param->timeout_microsecond =
				JIFFIES_TO_US(target_jiffies - now);
		else
			wait_param->timeout_microsecond = 0;

		return ret;
	}

	if (ret == 0) {
		timed out
	} else {
		condition was satisfied
	}

Even better, change the API so that 'timeout_microsecond' is an absolute time so you don't have accumulated errors if you're repeatedly interrupted.

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