[Powerdevil] [Bug 378445] kscreenlocker_greet occasionally freezes in malloc in signal handler

bugzilla_noreply at kde.org bugzilla_noreply at kde.org
Fri Apr 21 17:45:32 UTC 2017


https://bugs.kde.org/show_bug.cgi?id=378445

--- Comment #10 from rlk at alum.mit.edu ---
Note that frame 5 is a signal handler, so it's hardly surprising that frame 4
and frame 7 are unrelated.

I don't know this code, but it sure looks to me like something (in the second
trace, isValidBusName; in the first case, probably something different but I
didn't have debug symbols installed) was in the middle of free'ing something,
during which time kscreenlocker_greet() received a signal, and the signal
handler did a new QQmlProperty while the memory allocator was locked by the
free() called synchronously above it, so we have a deadlock.

My own guess -- and obviously this isn't my code -- is that something in
kscreenlocker_greet has set a signal handler (possibly a timeout) that is
allocating memory -- a no-no, unless you're using a re-entrant version of
malloc.

I'm pretty certain I had the right -debuginfo packages installed; rpm does the
version checking quite well.  And I don't think it's bad memory either; the
problem is consistently within the signal handler within kscreenlocker_greet,
and I don't see any other indications of bad memory on the system.

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