[PATCH] tracing: erase irqsoff trace with empty write

From: Bo Yan
Date: Mon Sep 11 2017 - 14:18:33 EST


One convenient way to erase trace is "echo > trace". However, this
is currently broken if the current tracer is irqsoff tracer. This
is because irqsoff tracer use max_buffer as the default trace
buffer.

Set the max_buffer as the one to be cleared when it's the trace
buffer currently in use.

Signed-off-by: Bo Yan <byan@xxxxxxxxxx>
---
kernel/trace/trace.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5360b7aec57a..1f91bdd9365b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4020,11 +4020,17 @@ static int tracing_open(struct inode *inode, struct file *file)
/* If this file was open for write, then erase contents */
if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
int cpu = tracing_get_cpu(inode);
+ struct trace_buffer *tr_buf = &tr->trace_buffer;
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+ if (tr->current_trace->print_max)
+ tr_buf = &tr->max_buffer;
+#endif

if (cpu == RING_BUFFER_ALL_CPUS)
- tracing_reset_online_cpus(&tr->trace_buffer);
+ tracing_reset_online_cpus(tr_buf);
else
- tracing_reset(&tr->trace_buffer, cpu);
+ tracing_reset(tr_buf, cpu);
}

if (file->f_mode & FMODE_READ) {
--
2.7.4