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>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 59de2525d303..d4e8b213a462 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -289,7 +289,7 @@ static struct sysrq_key_op sysrq_showstate_blocked_op = {
 
 static void sysrq_ftrace_dump(int key, struct tty_struct *tty)
 {
-        ftrace_dump();
+        ftrace_dump(DUMP_ALL);
 }
 static struct sysrq_key_op sysrq_ftrace_dump_op = {
         .handler        = sysrq_ftrace_dump,