Re: Add pselect, ppoll system calls.

["Mattias Engdegård" <mattias@virtutech.se>]

>> I don't have the POSIX specs handy, but I see no reason we could not let
>> it use a warpless monotonic clock.
>
>You have already one - the uptime of the system.

For example, yes. 

>Doing "Relative timeouts" with "gettimeofday()" is a strategic error.
>Specify the timeout und use (the return value of) times(2) for this.

Having an interface use absolute timeouts will avoid this strategic error,
simplify common code, and reduce the number of needed syscalls.

>Use "gettimeofday()" and similar just if (and only if) you communicate
>with the user (read: that is a pure user interface issue).

Of course, but it is not uncommon, perhaps because it's tedious to
convert between clock ticks and a struct timeval.
There is also the problem that the clock tick resolution has historically
been low (commonly 10 ms), which may cause bigger jitter in the longer term.
Also, a clock_t is frequently only 32 bits wide.