From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <68313859d562920ef34e99b7dc1a4046@plan9.jp>
To: 9fans@cse.psu.edu
From: Joel Salomon <chesky@plan9.jp>
Date: Tue, 12 Dec 2006 22:39:25 -0500
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Subject: [9fans] Interrupted alarm(2)
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I=E2=80=99ve been simulating preemptive multithreading using alarm(2) not=
es
and lots of stack smashing.  (I=E2=80=99ll have some questions about that
later, if things don=E2=80=99t go smooth.)

Anyhow, my taskfork looks like:
	void
	taskfork(ulong flags)
	{
		long	quantum;

		...

		quantum =3D alarm(0);	// stop timer and save time left

		...

		// back to our regularly scheduled programming...
		alarm(quantum =3D=3D 0 ? 1 : quantum);
	}
I included that ugly last line on the off chance that taskfork() is
called with less than a millisecond left and so alarm(0) will return
0.  Is this neccessary, or can alarm(0) not ever return 0?  Would it
be better to write:
		if(quantum)
			alarm(quantum);
		else
			postnote(PNPROC, getpid(), "alarm");
	}

--Joel