Answers to your questions follow: On 02/21/2011 12:08 AM, Phillip Lougher wrote: > "As far as mksquashfs is concerned, it is being invoked in the usual way > as an independent subprocess." > > What is the exact command line passed to Mksquashfs? (from looking at > the Transparent Archivist tool's source code it doesn't seem to be > passing any non-standard options). Right. No options were being passed during these tests, just the source directory and the target filepath. Then I tried -no-sparse which is, as you noted, irrelevant. Then I tried -noappend, which may or may not have solved the immediate problem. > "Sometimes -- not very often, maybe once in 30-60 invocations -- > mksquashfs simply hangs." > > Is this 30-60 invocations of Mksquashfs (by the Transparent Archivist > tool) or 30-60 invocations of the Transparent Archivist tool (which is > expected to invoke Mksquashfs itself multiple times)? Invocations of mksquashfs by TA. TA does successive approximations until it's satisfied that it has put as much into a given squashfs filesystem as will fit on a DVD or CD or whatever. > "Having made some of the filesystem it's supposed to be making, It stops > making the filesystem for no apparent reason. It continues to use a wee > bit of processing power after that -- very occasionally rising to the > top of the "top" display -- but it makes no observable progress on the > filesystem that it's supposed to be making. Once I left it running for 4 > days; no progress, and no resumption of work occurred during all that > time." > > With difficult to track down bugs (as this will be if it is a threading > issue)
(ain't that the truth!) > , even the smallest amount of clues can be useful. The fact that > Mksquashfs when hung occasionally rises to the top of the top display > suggests it is doing something (even though it is making no progress). > This in turns suggests the hang is a "livelock" issue rather than a > "deadlock" issue (in which case Mksquashfs will consume no CPU). When > Mksquashfs rises to the top of the top display how much CPU is it using? > and how often does it rise to the top of the top display? Not much CPU, but enough to be noticed on the top display maybe once a minute when the computer is otherwise idle. I don't know the % figure; I watched it flash by a couple of times and wasn't impressed by it. Maybe 5% or less for one top iteration, among many others in which it was effectively 0%. > As you've proved to be comfortable with modifying the Transparent > Archivist tool's source code to alter the Mksquashfs invocation > parameters, it would to useful to add the following options > > -no-progress -info > > This addresses two issues: > > First it gets rid of the progress bar (with the twirling progress > indicator), which as this is handled by a separate thread could be > completely responsible for Mksquashfs occasionally appearing in the top > of top - this is unlikely unless your system is doing absolutely nothing > else, but -no-progress eliminates that potential red herring. Ah. Good idea. Thanks! > Second it makes Mksquashfs display files as they are processed, in > particular it will show the files processed immediately before > Mksquashfs hangs. If over a number of hangs, the files processed before > the hang are identical it will strongly suggest there is something about > these files which are causing Mksquashfs to hang. This information will > be extremely useful. OK. I'll do this and send you a report. (Warning: each run takes over 24 hours, so don't expect immediate feedback.) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/722168 Title: mksquashfs hangs -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
