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It's been reported that running an SSH-2 session through PuTTY causes ntpd to lose time in 10ms steps, as if 100Hz interrupts are being lost. The same problem doesn't affect Telnet connections, though. Ref <C5EA7C1F01A7D311A44700508B95196C0730D8AB@004-h00028.wugo.intranet.wegener.nl> et seq., which mentions the platform as
PC DELL Latitude 610 with w2k pro Dutch with SP3 on AC Power.
As far as I can tell, noise_ultralight() and
noise_regular() are called even during a Telnet
session (they're stubs in PuTTYtel, but in PuTTY they go out
and hunt for noise even if no-one's ever going to consume it).
noise_get_heavy() is only called at the start of an SSH
session, so it shouldn't cause continuing problems, especially not ones
that go away when the session ends.
I think this narrows us down to noise_get_light(),
which is called every time the random pool is used, which
looks like being most packets in an SSH session, but never
in a Telnet session. noise_get_light() calls
GetSystemTime(), GetSystemTimeAdjustment()
and GetSystemPowerStatus().
By use of diagnostic builds we've narrowed the problem down to use
of GetSystemPowerStatus(), which is likely to be calling
the APM BIOS, which ISTR has to be done with interrupts disabled.
Update, 2004-03-18: the GetSystemPowerStatus()
call has been removed in an attempt to fix
`hard-hangs'. With luck, that should
make this problem go away too.
Audit trail for this semi-bug.