sleep forever in ACPI mode S3

echo 3 > /proc/acpi/sleep
 appears to work correctly on my IBM Thinkpad X20 -- except that it's
 impossible to wake the machine back up.
echo 1 > /proc/acpi/sleep
 has a similar problem -- ordinary keypresses don't wake the machine --
 but at least in this case the "power button" will bring the machine back.
 [neither the lid nor the sleep button do, though.]

Is this a known problem?  What keypresses are *supposed* to wake the
machine?  I looked through the code, but it looks like we punt off to the
ACPI firmware to do the actual sleep -- can anyone enlighten me on the
intended mechanism behind 'wake-from-sleep'?

[incidentally, i originally had the same problem others report with the
power button not only bringing the machine out of S1 but also rebooting
it: it was in fact acpid doing the reboot due to an easily-overlooked line
in its default.sh.  Previous posters have pointed to powerbtn.sh only.]
  --scott

[cc replies to me; i'm not on the list.]

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                         ( http://cscott.net/ )