alarm() bug in 4.2

[Keith Muller]

> Fortunately, there is an easy workaround; change the previous code
> to read:
>
>	for (...) {
>		oldmask = sigblock(1<<SIGALRM);
>		...
>		sigblock(oldmask);
>	}

This won't work, this will block off SIGTERM not SIGALRM. Sigblock()
requires that to block off signal i the i-th bit in the mask must
be set. (The bits are numbered from 1 to n). So that line must read:

		oldmask = sigblock(1 << (SIGALRM - 1));

Note this easily confused with select()'s mask which does NOT need to
have 1 subtracted since descriptors are numbered from 0 to n.

		Keith Muller
		UCSD Computer Center