From drsalists at gmail.com Fri Mar 2 09:29:50 2012 From: drsalists at gmail.com (Dan Stromberg) Date: Thu, 1 Mar 2012 15:29:50 -0800 Subject: [TUHS] "Slow system call" and EINTR Message-ID: I gather system calls can return EINTR only when they are "slow". True? What makes a system call "slow"? Is it the ability to block for a while? But I wouldn't think dup(2) would block, for example. (I -=Love=- *ix!) -------------- next part -------------- An HTML attachment was scrubbed... URL: From ramble1035 at dslextreme.com Fri Mar 2 09:59:53 2012 From: ramble1035 at dslextreme.com (ramble1035 @dslextreme.com) Date: Thu, 1 Mar 2012 15:59:53 -0800 Subject: [TUHS] "Slow system call" and EINTR In-Reply-To: References: Message-ID: On Thu, Mar 1, 2012 at 3:29 PM, Dan Stromberg wrote: > > I gather system calls can return EINTR only when they are "slow".  True? For a unique definition of "slow"... :) > What makes a system call "slow"?  Is it the ability to block for a while? > But I wouldn't think dup(2) would block, for example. >From my experience, a slow vs fast call is only partially based on time. It's more based on obtaining and releasing resources. A slow system call is one that might take a long time, and any resource allocations requested during the system call processing can be easily undone (returned). TTY input, as an example. Things like a disk request are *supposed* to be quick, but even if they're not, they involve allocating buffers, queueing disk requests, setting up possible interrupts or DMA, and other messy internal details. Aborting a pending disk request would be a substantial amount of effort. Thus, a disk request cannot be interrupted and it's classified as "fast". (or "not slow") This presents a few difficulties when you consider something like NFS, which acts like a disk request until it gets down to the network layer, where things might well take a long time. But interrupting and aborting this is not easy, which is why some NFS requests, when hung, stay hung even when you bang on Control-C for a while. Really simple things like dup, which involves a simple copy, would probably not block unless there were extreme issues with memory allocation or something. -- Chris From jfoust at threedee.com Wed Mar 14 02:09:04 2012 From: jfoust at threedee.com (John Foust) Date: Tue, 13 Mar 2012 11:09:04 -0500 Subject: [TUHS] ASR 37 teletype desired by LCM / Vulcan.com In-Reply-To: References: <20120201121214.55c73577@cnb.csic.es> <4F2A907D.9000000@fastmail.us> <89159FF1-5521-4890-A5F0-30DC9E5B7EC9@bsdimp.com> <20120202173623.GQ30634@mercury.ccil.org> <52BD3851-95AF-4DFC-8728-9F2DB1E1614C@bsdimp.com> Message-ID: <20120313170240.00A7C28E3D@minnie.tuhs.org> I forward a request from the Greenkeys (teletype) mailing list. The ASR 37 did upper- and lower-case. - John From: Cynde Moya To: greenkeys Date: Mon, 12 Mar 2012 22:01:51 +0000 Subject: [GreenKeys] Wanted : ASR 37 The Living Computer Museum is looking to purchase a working or restorable ASR 37 teletype. Do you have any leads? Thanks very much. Cynde Moya Librarian/Archivist, Vintage Computing Vulcan Inc 206 342-2385 http://www.vulcan.com http://www.LivingComputerMuseum.org