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From: "saugustine at google dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug server/16168] New: Signal heavy execution + repeated breakpoint
 locks up gbserver
Date: Wed, 13 Nov 2013 20:28:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gdb
X-Bugzilla-Component: server
X-Bugzilla-Version: HEAD
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: saugustine at google dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P2
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http://sourceware.org/bugzilla/show_bug.cgi?id=16168

            Bug ID: 16168
           Summary: Signal heavy execution + repeated breakpoint locks up
                    gbserver
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: server
          Assignee: unassigned at sourceware dot org
          Reporter: saugustine at google dot com

Created attachment 7276
  --> http://sourceware.org/bugzilla/attachment.cgi?id=7276&action=edit
files to reproduce.

The attached tar file includes a source file, a bash script, and a gdb script
which exposes a bug in gdbserver's signal handling.

You can simply run sh doit.sh to reproduce the problem.

gdbserver attaches to a multi-threaded application, which is also taking
SIGPROF signals.

The program repeatedly hits a breakpoint in some of the threads, and continues.

At some point, the SIGPROF will trigger a situation where a thread has a
pending signal, so gdbserver elects not to restart all threads.

In the included gdbserver.log file, this is the line: "Not resuming, all-stop
and found an LWP with pending status."

The only thread ever restarted is the pending one. Eventually, this thread runs
out of work and the system locks up.

There is a race involved, so you may need to run it a couple of times.
Sometimes it happens very early, and these are the easiest logs to study.

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