From: jmk@plan9.bell-labs.com
To: 9fans@cse.psu.edu
Subject: Re: [9fans] Performance
Date: Thu, 10 May 2001 13:21:40 -0400 [thread overview]
Message-ID: <20010510172143.06C70199F9@mail.cse.psu.edu> (raw)
On Thu May 10 11:31:55 EDT 2001, DAGwyn@null.net wrote:
> Richard Miller wrote:
> > Isn't there a race condition here even on a uniprocessor? The scan
> > of the run queue and call to HLT are done with interrupts enabled:
>
> Yes, the canonical solution, which addresses HLT on MP systems
> as well, is that whatever modifies the run queue always as a side
> effect wakes up all the dispatchers. Some platforms support use
> of a software interrupt just as though it were a hardware
> interrupt; on others a kludge would be required, or else just
> leave it up to the clock interrupt.
Waking up other processors would require interprocessor interrupts
and that way lies madness.
A software interrupt on a uniprocessor wouldn't fix the race.
I think the correct kludge is to wait for the clock interrupt.
next reply other threads:[~2001-05-10 17:21 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-05-10 17:21 jmk [this message]
2001-05-11 8:33 ` Douglas A. Gwyn
-- strict thread matches above, loose matches on Subject: below --
2001-05-11 13:52 jmk
2001-05-09 14:47 Richard Miller
2001-05-10 15:14 ` Douglas A. Gwyn
2001-05-09 13:03 presotto
2001-05-09 12:57 jmk
2001-05-09 8:58 forsyth
2001-05-09 6:03 nemo
2001-05-08 21:33 Russ Cox
2001-05-09 2:09 ` Ronald G Minnich
2001-05-10 15:15 ` Douglas A. Gwyn
2001-05-08 21:25 jmk
2001-05-08 18:20 jmk
2001-05-09 8:29 ` Peter Schay
2001-05-08 17:54 nemo
2001-05-08 18:46 ` Scott Schwartz
2001-05-08 17:42 Fariborz 'Skip' Tavakkolian
2001-05-08 18:07 ` aam396
2001-05-08 22:38 ` Boyd Roberts
2001-05-08 17:40 presotto
2001-05-08 18:45 ` Scott Schwartz
2001-05-09 5:35 ` Franklin Robert Araujo Frana
2001-05-10 8:43 ` Juhani Forsman
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