path: root/Documentation/trace
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authorFrederic Weisbecker <fweisbec@gmail.com>2010-04-18 19:08:41 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2010-04-21 23:11:42 +0200
commitcecbca96da387428e220e307a9c945e37e2f4d9e (patch)
tree2edefda983658c19a8f2b38ff951a3046597a4f7 /Documentation/trace
parentb15c7b1cee119999e9eafcd602d24a595e77adac (diff)
tracing: Dump either the oops's cpu source or all cpus buffers
The ftrace_dump_on_oops kernel parameter, sysctl and sysrq let one dump every cpu buffers when an oops or panic happens. It's nice when you have few cpus but it may take ages if have many, plus you miss the real origin of the problem in all the cpu traces. Sometimes, all you need is to dump the cpu buffer that triggered the opps, most of the time it is our main interest. This patch modifies ftrace_dump_on_oops to handle this choice. The ftrace_dump_on_oops kernel parameter, when it comes alone, has the same behaviour than before. But ftrace_dump_on_oops=orig_cpu will only dump the buffer of the cpu that oops'ed. Similarly, sysctl kernel.ftrace_dump_on_oops=1 and echo 1 > /proc/sys/kernel/ftrace_dump_on_oops keep their previous behaviour. But setting 2 jumps into cpu origin dump mode. v2: Fix double setup v3: Fix spelling issues reported by Randy Dunlap v4: Also update __ftrace_dump in the selftests Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Diffstat (limited to 'Documentation/trace')
1 files changed, 4 insertions, 2 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 03485bfbd79..52011815c90 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1337,12 +1337,14 @@ ftrace_dump_on_oops must be set. To set ftrace_dump_on_oops, one
can either use the sysctl function or set it via the proc system
- sysctl kernel.ftrace_dump_on_oops=1
+ sysctl kernel.ftrace_dump_on_oops=n
- echo 1 > /proc/sys/kernel/ftrace_dump_on_oops
+ echo n > /proc/sys/kernel/ftrace_dump_on_oops
+If n = 1, ftrace will dump buffers of all CPUs, if n = 2 ftrace will
+only dump the buffer of the CPU that triggered the oops.
Here's an example of such a dump after a null pointer
dereference in a kernel module: