Updated trace-cmd packages that fix two bugs and add one enhancement are now available for Red Hat Enterprise Linux 6.
The trace-cmd packages contain a command-line tool that interfaces with the ftrace utility in the kernel.
- The trace-cmd extract command read a buffer multiple times even after an EOF condition. Consequently, the output of the trace-cmd command contained duplicate data. With this update, the trace-cmd utility has been modified to respect the EOF condition and avoid duplication of data in its output.
- When using the latency tracer, the start_threads() function was not called. Calling the stop_threads() function without first calling start_threads() caused the trace-cmd record command to terminate with a segmentation fault because PIDs were not initialized. Consequently, the trace.dat file was not generated. With this update, stop_threads() is not called unless start_threads() is called first. As a result, the segmentation fault no longer occurs.
- Previously, the trace-cmd record command was able to filter ftrace data based on a single PID only. With this update, multiple PIDs can be specified by using the "-P" option.
Users of trace-cmd are advised to upgrade to these updated packages, which fix these bugs and add this enhancement.