[Desktop-packages] [Bug 967416] Re: inkscape crashed with SIGSEGV in file_save()
@jazzynico Thanks, I think that would solve the crash, however some issues come to mind with that solution: 1. It would introduce some global state, which would be tricky to reason about for anyone not familiar with the specifics. This is particularly complicated since it appears from the code everything is on the same thread. 2. Other UI actions aside from saving are likely to be affected, any changes in each may silently trigger unsuspecting behavior due to this in the future (this may actually be causing some other bugs after saving as well?) I didn't mention, but this main_loop can also cause multiple script saves to chain on the call stack: for example, if another save is performed instead of an exit, that save is actually running yet another file_save call (and thus running another g_main_loop_run). At this point there's 3 different entry points on the stack into file_save from the same thread, and although it may technically work, to me it seems brittle. I think the culprit here is the extra main loop being run in the script, and I think the only clean solution would be to remove it completely. Upon closer investigation I think the only time it's actually stopped (in the context of saving) is if the appropriate file_listeners (stdout, stderr) have read data from the spawned script process. Although there is a Script::cancelProcessing, I think this is only called from an Extension Effect. Would displaying a dialog window (replacing the _main_loop entirely) here instead work? This should block and the file_listeners and cancellation could then simply close it when completed. I'll see if I can play around with a solution, again my GTK experience is very basic so maybe there's a better approach. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to inkscape in Ubuntu. https://bugs.launchpad.net/bugs/967416 Title: inkscape crashed with SIGSEGV in file_save() Status in Inkscape: A Vector Drawing Tool: Triaged Status in inkscape package in Ubuntu: Triaged Bug description: Occurred when I closed Inkscape. ProblemType: Crash DistroRelease: Ubuntu 12.04 Package: inkscape 0.48.3.1-0ubuntu2 ProcVersionSignature: Ubuntu 3.2.0-20.33-generic 3.2.12 Uname: Linux 3.2.0-20-generic x86_64 ApportVersion: 1.95-0ubuntu1 Architecture: amd64 CrashCounter: 1 Date: Wed Mar 28 15:01:15 2012 ExecutablePath: /usr/bin/inkscape InstallationMedia: Ubuntu 12.04 LTS Precise Pangolin - Alpha amd64 (2029.1) ProcCmdline: inkscape /home/username/MyKaryotes/graphics/cell.svg ProcEnviron: LANG=en_US.UTF-8 SHELL=/bin/bash SegvReason: reading NULL VMA Signal: 11 SourcePackage: inkscape Title: inkscape crashed with SIGSEGV in sp_file_save_dialog() UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo To manage notifications about this bug go to: https://bugs.launchpad.net/inkscape/+bug/967416/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
[Desktop-packages] [Bug 967416] Re: inkscape crashed with SIGSEGV in file_save()
I've attached a proposed patch. One thing of note is that this actually keeps the Glib::MainLoop, after reading more into it, it appears that a recursive call to running a main loop is supported. The actual problem is that this was reusing the default MainContext which had all of the original input sources. This patch builds a new MainContext for the new MainLoop, and with each file_listener::init connects the stdout and stderr it to this new context. This causes the expected blocking UI behavior until the script has completed saving since the new context shouldn't have any other sources. Unfortunately this does cause the UI to appear to be hung until the script completes the save, but given Johan's statement it sounds like it might be a reasonable fix until multithreading can be added. ** Patch added: bug967416.patch https://bugs.launchpad.net/ubuntu/+source/inkscape/+bug/967416/+attachment/4296282/+files/bug967416.patch -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to inkscape in Ubuntu. https://bugs.launchpad.net/bugs/967416 Title: inkscape crashed with SIGSEGV in file_save() Status in Inkscape: A Vector Drawing Tool: Triaged Status in inkscape package in Ubuntu: Triaged Bug description: Occurred when I closed Inkscape. ProblemType: Crash DistroRelease: Ubuntu 12.04 Package: inkscape 0.48.3.1-0ubuntu2 ProcVersionSignature: Ubuntu 3.2.0-20.33-generic 3.2.12 Uname: Linux 3.2.0-20-generic x86_64 ApportVersion: 1.95-0ubuntu1 Architecture: amd64 CrashCounter: 1 Date: Wed Mar 28 15:01:15 2012 ExecutablePath: /usr/bin/inkscape InstallationMedia: Ubuntu 12.04 LTS Precise Pangolin - Alpha amd64 (2029.1) ProcCmdline: inkscape /home/username/MyKaryotes/graphics/cell.svg ProcEnviron: LANG=en_US.UTF-8 SHELL=/bin/bash SegvReason: reading NULL VMA Signal: 11 SourcePackage: inkscape Title: inkscape crashed with SIGSEGV in sp_file_save_dialog() UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo To manage notifications about this bug go to: https://bugs.launchpad.net/inkscape/+bug/967416/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
[Desktop-packages] [Bug 967416] Re: inkscape crashed with SIGSEGV in file_save()
I thought I might take a crack at this since it looked interesting. I apologize for the length, I've added debugging details so hopefully it's clear. I'm new to the codebase and GTK, so I've added a lot so it can be double-checked. I don't think this is a threading problem. Rather, it looks like a reentrant issue with with running a script. I've attached two full stacktraces that give some more details prior to the actual crash, I reference them below: The first, stacktrace_remove_desktop.txt, shows the backtrace at the point where the last desktop is destroyed, SP_ACTIVE_DESKTOP is effectively set to NULL. For brevity I'm posting a snippet: #0 Inkscape::Application::remove_desktop #1 sp_desktop_widget_dispose ~snip~ #14 sp_ui_close_all ~snip~ #34 g_main_loop_run ~snip~ #35 Inkscape::Extension::Implementation::Script::execute #36Inkscape::Extension::Implementation::Script::save #37 Inkscape::Extension::Output::save #38 Inkscape::Extension::save #39 file_save at file.cpp:666 #40 sp_file_save_dialog ~snip~ #60 g_main_loop_run #61 IA__gtk_main #62 sp_main_gui #63 __libc_start_main At this point it starts becoming clear that the Extension::Script::execute has launched another main loop while it waits on the child python script to complete execution, or at least Script::cancelProcessing is called. I believe the script has not completed, therefore the input handler is run in the context of this new main loop, the UI saves and deletes the desktops (including SP_ACTIVE_DESKTOP). At some point the inner g_main_loop_run then returns, and eventually unwinds back to file_save, this then continues and hits the failure at the added debug messages and segfaults when dereferencing in file_save. I've also added a stacktrace_after_initial_save_xcf.txt where I simply saved to a XCF file, waited a second then grabbed a backtrace to verify that a second g_main_loop was still executing. Again, I'm not familiar enough with GTK, but I suspect this second loop is handling the window events, so it actually appears that the UI thread has returned from the file save and is handling event in the real loop, but in fact the stack is still sitting deep within the file_save call. I think this explains the problems where it happens to only occur when initially saving with certain formats (those that run scripts). I believe it also explains what appeared to be a threading issue since it was not 100% reproducible, actually it's more of a process-race on whether the script can complete before exiting. I'm not really sure of the fix here, again I'm new to the codebase and I don't know the Extension/Scripts requirements. I'm not entirely sure why there's a need for a Glib::MainLoop in the script - as I would think that any script work would be done in the spawn_async_with_pipes. Or, maybe this intentionally/cleverly hides blocking on the UI thread for script results. ** Attachment added: stacktrace.zip https://bugs.launchpad.net/inkscape/+bug/967416/+attachment/4295626/+files/stacktrace.zip -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to inkscape in Ubuntu. https://bugs.launchpad.net/bugs/967416 Title: inkscape crashed with SIGSEGV in file_save() Status in Inkscape: A Vector Drawing Tool: Triaged Status in inkscape package in Ubuntu: Triaged Bug description: Occurred when I closed Inkscape. ProblemType: Crash DistroRelease: Ubuntu 12.04 Package: inkscape 0.48.3.1-0ubuntu2 ProcVersionSignature: Ubuntu 3.2.0-20.33-generic 3.2.12 Uname: Linux 3.2.0-20-generic x86_64 ApportVersion: 1.95-0ubuntu1 Architecture: amd64 CrashCounter: 1 Date: Wed Mar 28 15:01:15 2012 ExecutablePath: /usr/bin/inkscape InstallationMedia: Ubuntu 12.04 LTS Precise Pangolin - Alpha amd64 (2029.1) ProcCmdline: inkscape /home/username/MyKaryotes/graphics/cell.svg ProcEnviron: LANG=en_US.UTF-8 SHELL=/bin/bash SegvReason: reading NULL VMA Signal: 11 SourcePackage: inkscape Title: inkscape crashed with SIGSEGV in sp_file_save_dialog() UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo To manage notifications about this bug go to: https://bugs.launchpad.net/inkscape/+bug/967416/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
