waitpid() with WUNTRACED flag? (was Re: Hang on ctrl+Z after the MPSAFE tsleep/wakeup commit)

[Matthew Dillon]

:While this has been fixed, I realized that I overlooked another
:similar problem; try running vipw, suspend it with ctrl-Z and
:continue with `fg'; the shell immediately reports that vipw has been
:suspended(processes are marked as `TL' by ps command); another `fg'
:seems to continue it, but vi(or whatever editor invoked by vipw)
:doesn't handle the screen properly, even though it's responding to
:the keystrokes.
:Attached is a small code fragment that demonstrates the problem.
:BTW, it behaves differently on -CURRENT and 1.2.6-RELEASE;
:on -CURRENT, waitpid() returns after `fg' command followed by a ctrl-Z,
:while on 1.2.6-RELEASE it never returns when suspended or continued.
:Without WUNTRACED flag, the code seems to work the same way on both
:versions of the OS.
:Too bad I couldn't find it before the new release.

    We haven't released yet!  I can reproduce the same problem so I'll
    track it down and get it fixed before the release.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>