tracing: add cpu_file intialization for ftrace_dump

Impact: fix to ftrace_dump output corruption

The commit: b04cc6b1f6398b0e0b60d37e27ce51b4899672ec
  tracing/core: introduce per cpu tracing files

added a new field to the iterator called cpu_file. This was a handle
to differentiate between the per cpu trace output files and the
all cpu "trace" file. The all cpu "trace" file required setting this
to TRACE_PIPE_ALL_CPU.

The problem is that the ftrace_dump sets up its own iterator but was
not updated to handle this change. The result was only CPU 0 printing
out on crash and a lot of "<0>"'s also being printed.

Reported-by: Thomas Gleixner <tglx@linuxtronix.de>
Tested-by: Darren Hart <dvhtc@us.ibm.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c8abbb0c8397..ab5cbcae43a1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3918,8 +3918,10 @@ void ftrace_dump(void)
 
         printk(KERN_TRACE "Dumping ftrace buffer:\n");
 
+        /* Simulate the iterator */
         iter.tr = &global_trace;
         iter.trace = current_trace;
+        iter.cpu_file = TRACE_PIPE_ALL_CPU;
 
         /*
          * We need to stop all tracing on all CPUS to read the