tracing/function-graph-tracer: prevent hangs during self-tests

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Impact: detect tracing related hangs

Sometimes, with some configs, the function graph tracer can make
the timer interrupt too much slow, hanging the kernel in an endless
loop of timer interrupts servicing.

As suggested by Ingo, this patch brings a watchdog which stops the
selftest after a defined number of functions traced, definitely
disabling this tracer.

For those who want to debug the cause of the function graph trace
hang, you can pass the ftrace_dump_on_oops kernel parameter to dump
the traces after this hang detection.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1237694675-23509-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

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This commit is contained in:

Frederic Weisbecker 2009-03-22 05:04:35 +01:00 • committed by Ingo Molnar

parent ac199db018

commit cf586b61f8

2 changed files with 60 additions and 4 deletions

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26

kernel/trace/trace.c

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38

kernel/trace/trace_selftest.c

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