Date: Wed, 30 Jun 1999 19:19:18 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Terry Lambert <tlambert@primenet.com>, bright@rush.net (Alfred Perlstein), smp@FreeBSD.ORG, tlambert@primenet.com Subject: Re: async call gates Message-ID: <199907010219.TAA42502@apollo.backplane.com> References: <199907010100.SAA13352@usr09.primenet.com> <199907010154.SAA42283@apollo.backplane.com>
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: So in my embedded OS I had a domsg() and a sendmsg() API. The user
: process constructs the message and calls one or the other entry point.
: If the user requested a synchronous call AND the device happens to run
: the request synchronously, the OS doesn't bother even queueing the
: message up to the device. It calls the device entry, sees that the
: device ran the message synchronously, and returns. The result is an
: operation that runs just as quickly as a normal system call might since
: the added complexity of queueing and dequeueing the message just doesn't
: happen.
Plus it would be fairly easy to make the message-entry itself SMP-capable
(i.e. allow several threads to attempt to sendmsg() the same message
simultaniously, in which one succeeds and the other fails due to the
message being in-progress. This would be useful for dispatching
software interrupts).
-Matt
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