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Message #06564
[Bug 1576989] Re: stale lock files freeze apps
QA managed to reproduce it still. However, from going through the git
still, there is a untried combination of patches that we haven't yet
backported so I will rebuild the silo.
** Also affects: qtbase-opensource-src (Ubuntu RTM)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1576989
Title:
stale lock files freeze apps
Status in Canonical System Image:
Confirmed
Status in qtbase-opensource-src package in Ubuntu:
Confirmed
Status in qtbase-opensource-src package in Ubuntu RTM:
New
Bug description:
Debugging why the Notes app would freeze for some people, I found
there were some stale .lock files around. Those .lock files are
autocreated by QSettings (with QLockFile) when this file is edited.
Problem is, that it sometimes seems to happen that the app is
suspended by our lifecycle and then killed (either by closing from
spread or OOM killed) and those .lock files stick around. I have
implemented a workaround in the notes app[1] to clear up those stale
locks when the app starts app, however, today I ran twice in a row
into the issue that the very same happened to music app. It would just
freeze on startup and never come back. Digging around a bit I found
such a stale lock file on its config file which is created with the
QML Settings element. This implies that every app using QSettings or
QML Settings {} are potentially affected. I suspect many more app
freezes can be traced down to this.
Now, there is some code in Qt to detect stale lock files [2], however,
not sure why it doesn't detect those lock files as stale ones and
decides to wait on them forever though. Probably a bug in the code or
some of the wrong #ifdefs are triggered for our package builds.
[1] https://code.launchpad.net/~mzanetti/reminders-app/remove-stale-lock-files/+merge/293355
[2] http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/io/qlockfile_unix.cpp
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References