tree e8a9ded926402162b0e0cd6cd2136f05f28862dd
parent 9ed19c7695670d00455c1de4682d5c7f14618689
author Steven Rostedt (VMware) <rostedt@goodmis.org> 1492618028 -0400
committer Steven Rostedt (VMware) <rostedt@goodmis.org> 1492625948 -0400

tracing: Allocate the snapshot buffer before enabling probe

Currently the snapshot trigger enables the probe and then allocates the
snapshot. If the probe triggers before the allocation, it could cause the
snapshot to fail and turn tracing off. It's best to allocate the snapshot
buffer first, and then enable the trigger. If something goes wrong in the
enabling of the trigger, the snapshot buffer is still allocated, but it can
also be freed by the user by writting zero into the snapshot buffer file.

Also add a check of the return status of alloc_snapshot().

Cc: stable@vger.kernel.org
Fixes: 77fd5c15e3 ("tracing: Add snapshot trigger to function probes")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>