Messages in this thread | | | Date | Fri, 08 Feb 2002 20:19:15 +0000 | From | Anton Altaparmakov <> | Subject | Linus' email account is full. - Fwd: Mail System Error - Returned Mail |
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Linus' email account appears to be full if we can believe this returned email:
>Envelope-to: aia21@cus.cam.ac.uk >To: aia21@cam.ac.uk >From: Mail Administrator <Postmaster@transmet.com> >Reply-To: Mail Administrator <Postmaster@transmet.com> >Subject: Mail System Error - Returned Mail >Date: Fri, 8 Feb 2002 15:14:23 -0500 > >This Message was undeliverable due to the following reason: > >The user(s) account is temporarily over quota. > ><usr3189@transmet.com> > >Please reply to Postmaster@transmet.com >if you feel this message to be in error. >Reporting-MTA: dns; imta04a2.registeredsite.com >Arrival-Date: Fri, 8 Feb 2002 15:14:23 -0500 >Received-From-MTA: dns; orange.csi.cam.ac.uk (131.111.8.77) > >Final-Recipient: RFC822; <torvalds@transmet.com> >Action: failed >Status: 4.2.2 >X-Actual-Recipient: RFC822; <usr3189@transmet.com> >Received: from orange.csi.cam.ac.uk ([131.111.8.77]) > by imta04a2.registeredsite.com with ESMTP > id > <20020208201423.QUCD3217.imta04a2.registeredsite.com@orange.csi.cam.ac.uk> > for <torvalds@transmet.com>; Fri, 8 Feb 2002 15:14:23 -0500 >Received: from tmd.christs.cam.ac.uk ([131.111.219.75] helo=tmd.cam.ac.uk) > by orange.csi.cam.ac.uk with esmtp (Exim 3.34 #1) > id 16ZHOo-0007Tk-00; Fri, 08 Feb 2002 20:13:34 +0000 >Message-Id: <5.1.0.14.2.20020208174632.00b0dad0@pop.cus.cam.ac.uk> >X-Sender: aia21@pop.cus.cam.ac.uk >X-Mailer: QUALCOMM Windows Eudora Version 5.1 >Date: Fri, 08 Feb 2002 20:14:32 +0000 >To: nigel@nrg.org >From: Anton Altaparmakov <aia21@cam.ac.uk> >Subject: Re: [RFC] New locking primitive for 2.5 >Cc: Christoph Hellwig <hch@ns.caldera.de>,Ingo Molnar <mingo@elte.hu>, > yodaiken <yodaiken@fsmlabs.com>,Martin Wirth <Martin.Wirth@dlr.de>, > linux-kernel <linux-kernel@vger.kernel.org>,akpm <akpm@zip.com.au>, > torvalds <torvalds@transmet.com>,rml <rml@tech9.net> >In-Reply-To: <Pine.LNX.4.40.0202080838230.3883-100000@cosmic.nrg.org> >References: <200202081231.g18CV7e31341@ns.caldera.de> >Mime-Version: 1.0 >Content-Type: text/plain; charset="us-ascii"; format=flowed > >At 16:51 08/02/02, Nigel Gamble wrote: >> > No. i_sem should be split into a spinlock for short-time accessed >> > fields that get written to even if the file content is only read (i.e. >> > atime) and a read-write semaphore. >> >>Read-write semaphores should never be used. As others have pointed out, >>they cause really intractable priority inversion problems (because a >>high priority writer will often have to wait for an unbounded number of >>lower priority readers, some of which may have called a blocking >>function while holding the read lock). >> >>Note that I'm not talking about read-write spinlocks, which are (or >>should be) held for a short, bounded time and can't be held over a >>blocking call, so they are not quite so problematic. > >Read-write semaphores have their use and the current Linux implementation >(big reader/occasional writer) guarantees that the writer is not starved >as incoming read locks are put to sleep as soon as a write lock request >comes in, even if that is sleeping waiting for the old readlocks to be >released (unless the readers are holding the semaphore forever in which >case this is the programmers fault and not the rw semaphore >implementations fault). [I should add I only am familliar with the i386 >implementation but I assume the others are the same.] > >The value of allowing multiple cpus to read the same data simultaneously >by far offsets the priority problems IMVHO. At least the way I am using rw >semaphores in ntfs it is. Readlocks are grabbed loads and loads of times >to serialize meta data access in the page cache while writelocks are a >minute number in comparison and because the data required to be accessed >may not be cached in memory (page cache page is not read in, is swapped >out, whatever) a disk access may be required which means a rw spin lock is >no good. In fact ntfs would be the perfect candidate for automatic rw >combi locks where the locking switches from spinning to sleeping if the >code path reaches a disk access. I can't use a manually controlled lock as >the page cache lookups are done via the mm/filemap.c access functions >which are the only ones who can know if a disk access is required or not >so ntfs would never know if it is going to sleep or not so unless the >locks had autodetection of whether to spin or sleep they would be useless. > >I guess the point I am trying to make is that both rw semaphores and combi >locks are not bad per se but, as all other locking mechanisms, they should >be used in situations appropriate for their locktype and their >implementation... > >Anton > > >-- > "I've not lost my mind. It's backed up on tape somewhere." - Unknown >-- >Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) >Linux NTFS Maintainer / WWW: http://linux-ntfs.sf.net/ >ICQ: 8561279 / WWW: http://www-stu.christs.cam.ac.uk/~aia21/ >
-- "I've not lost my mind. It's backed up on tape somewhere." - Unknown -- Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) Linux NTFS Maintainer / WWW: http://linux-ntfs.sf.net/ ICQ: 8561279 / WWW: http://www-stu.christs.cam.ac.uk/~aia21/
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