The upstream patch in question in commit 72906e1 was cherry-picked into
Ubuntu's 3.16 kernel backport branch (called lts-utopic). The version
check should also include this branch.
The other backport branch, lts-vivid, and all following ones will be
covered by the standard
b02a8b7...
by
Martin Leisener <email address hidden>
Fix: Building the event list fails on fragmented memory
On a small arm imx6 solo with 256MB RAM it often happens that memory
becomes fragmented rather quickly, so that kmalloc will not be able to
get enough consecutive pages (enocuntered for example if you enable all
kernel events: lttng enable-event -k syscall --all).
This patch switches the allocation to vmalloc. Tested for x86 on Ubuntu
12.04 Lts and on imx6 solo 256MB RAM
If this patch is not applied, you can identify low and/or fragmented
memory failures by looking at the kernel ring buffer (please ignore DMA,
it is due to some memory setup misconfiguration, should read Normal):
Fix: use after free on metadata cache reallocation
When the metadata cache is expanded (reallocated) by
lttng_metadata_printf(), the metadata cache reader
(lttng_metadata_output_channel()) may use freed memory, because the
metadata cache is not protected from concurrent read accesses. The
metadata cache updates are protected from each other by the sessions
mutex, but metadata cache reads do not hold the sessions mutex.
Actually, the comment on top of lttng_metadata_output_channel() stating
"We have exclusive access to our metadata buffer (protected by the
sessions_mutex)" is simply wrong, because this mutex is never held when
calling lttng_metadata_output_channel().
Promote the per-stream lock to the metadata cache used by each of those
metadata streams, thus ensuring mutual exclusion between metadata cache
reallocation and readers.
