Hello Will Berkeley, Tidy Bot, Mike Percy, Kudu Jenkins,

I'd like you to reexamine a change. Please visit


to look at the new patch set (#2).

Change subject: KUDU-2291 (part 5): allow collecting stack traces asynchronously

KUDU-2291 (part 5): allow collecting stack traces asynchronously

This removes the global variable previously used to communicate between
a stack trace collector and the stack trace target. The global variable
had the downside of allowing only a single stack trace operation in
flight at a time, which means that for use cases where we want to
capture the trace of a bunch of threads, we needed to do so serially.

For use cases like process-wide traces this could make debugging a bit
tricky. For example, because of the skew in time between collecting
the stack of thread A and the stack of thread B, it's possible that
the traces could show them holding the same lock, which we know to be
impossible. Getting the collection time as close as possible to
"simultaneous" can reduce the possibility of these kind of
strange-looking results.

The actual mechanism to do this is slightly tricky. Rather than
duplicate the full description here, check the comments in the
implementation. In particular, StackTraceCollector::RevokeSigData()
explains the complexity of not knowing whether our signal will ever be

A new unit test shows the pattern, and this also updates the stack
servlet to send the signals to all of the threads as close as possible
to "the same time".

Change-Id: Ie4d7789bb1272db033df4685f46eaf8483ec7be1
M src/kudu/server/default_path_handlers.cc
M src/kudu/util/debug-util-test.cc
M src/kudu/util/debug-util.cc
M src/kudu/util/debug-util.h
4 files changed, 306 insertions(+), 109 deletions(-)

  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/18/9318/2
To view, visit http://gerrit.cloudera.org:8080/9318
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Ie4d7789bb1272db033df4685f46eaf8483ec7be1
Gerrit-Change-Number: 9318
Gerrit-PatchSet: 2
Gerrit-Owner: Todd Lipcon <t...@apache.org>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Mike Percy <mpe...@apache.org>
Gerrit-Reviewer: Tidy Bot
Gerrit-Reviewer: Will Berkeley <wdberke...@gmail.com>

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