On 6/17/21 6:05 PM, Charan Teja Kalla wrote:

The wait_event/freezable_timeout() documentation says that:
 * Returns:
 * 0 if the @condition evaluated to %false after the @timeout elapsed,
			or
 * 1 if the @condition evaluated to %true after the @timeout elapsed,
 * or the remaining jiffies (at least 1) if the @condition evaluated
 * to %true before the @timeout elapsed.

which means the condition must be evaluated to true or timeout should be
elapsed for the function wait_event_freezable_timeout() to return.

Please check the macro implementation of __wait_event, where it will be
in for(;;) till the condition is evaluated to true or timeout happens.
#define __wait_event_freezable_timeout(wq_head, condition, timeout)

        ___wait_event(wq_head, ___wait_cond_timeout(condition),

                      TASK_INTERRUPTIBLE, 0, timeout,

                      __ret = freezable_schedule_timeout(__ret))

Thus the plain wakeup of kcompactd don't do the proactive compact work.
And so we should identify its wakeup for proactive work with a separate
flag.

OK, you're right, I forgot that the macro has the for loop to guard against
spurious wakeups.