unity-system-compositor locked up in __libc_do_syscall()

Stacktrace:
 #0 0xb6d89d44 in ?? ()
 No symbol table info available.
 #1 0xb6d8795c in ?? ()
 No symbol table info available.
 Backtrace stopped: previous frame identical to this frame (corrupt stack?)
StacktraceTop:
 ?? ()
 ?? ()

Thank you for your report!

However, processing it in order to get sufficient information for the
developers failed (it does not generate a useful symbolic stack trace). This
might be caused by some outdated packages which were installed on your system
at the time of the report:

package libmirplatform11 does not exist, ignoring
no debug symbol package found for libusb-0.1-4
systemd version 219-7ubuntu6vividtouch1 required, but 219-7ubuntu6 is available
libsystemd0 version 219-7ubuntu6vividtouch1 required, but 219-7ubuntu6 is available
libandroid-properties1 version 0.1.0+git20151016+6d424c9-0ubuntu5~overlay1 required, but 0.1.0+git20131207+e452e83-0ubuntu39 is available
no debug symbol package found for libandroid-properties1
package libmircookie2 does not exist, ignoring
package libmirserver37 does not exist, ignoring
no debug symbol package found for cgmanager
unity-system-compositor version 0.4.1+15.04.20160203-0ubuntu1 required, but 0.0.5+15.04.20150227-0ubuntu1 is available
no debug symbol package found for unity-system-compositor
no debug symbol package found for libgpg-error0
no debug symbol package found for dmsetup
no debug symbol package found for libisc-export95
package libmirprotobuf3 does not exist, ignoring
no debug symbol package found for shared-mime-info
udev version 219-7ubuntu6vividtouch1 required, but 219-7ubuntu6 is available
no debug symbol package found for sysvinit-utils
no debug symbol package found for libcgmanager0
libpam-systemd version 219-7ubuntu6vividtouch1 required, but 219-7ubuntu6 is available
no debug symbol package found for libselinux1
libudev1 version 219-7ubuntu6vividtouch1 required, but 219-7ubuntu6 is available
no debug symbol package found for libdevmapper1.02.1
no debug symbol package found for gpgv
no debug symbol package found for libbz2-1.0
no debug symbol package found for debianutils
no debug symbol package found for libelf1
no debug symbol package found for libapparmor1
no debug symbol package found for libisccfg-export90
no debug symbol package found for initscripts
no debug symbol package found for libdns-export100
no debug symbol package found for gnupg
package libmirclient9 does not exist, ignoring
no debug symbol package found for ifupdown
no debug symbol package found for libcryptsetup4
no debug symbol package found for libprotobuf-lite9
no debug symbol package found for libaudit1
no debug symbol package found for libsemanage1
no debug symbol package found for libkmod2
no debug symbol package found for libxkbcommon0
no debug symbol package found for libirs-export91
package libmircommon5 does not exist, ignoring
no debug symbol package found for perl-base
no debug symbol package found for iproute2
no debug symbol package found for libhybris
no debug symbol package found for liblttng-ust0
libudev1 version 219-7ubuntu6vividtouch1 required, but 219-7ubuntu6 is available
no debug symbol package found for libhardware2
no debug symbol package found for libhybris-common1
libandroid-properties1 version 0.1.0+git20151016+6d424c9-0ubuntu5~overlay1 required, but 0.1.0+git20131207+e452e83-0ubuntu39 is available
no debug symbol package found for libandroid-properties1
no debug symbol package found for...

One of the threads is waiting on a lock in Mir's SystemCompositorWindowManager::add_display() - I see no other thread touching that lock, and there's a bug in the lock handling of that class. (See linked branch.)

The SystemCompositorWindowManager::remove_surface() bug may not be the whole problem but needs to be eliminated.

Bug 1536662 would manifest similarly if you didn't wait the full 30 seconds. Although I can't yet see evidence of bug 1536662 in the stack traces.

Can you point out the branch or revision where this was fixed?

lp:mir r3288