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authorHiraku Toyooka <hiraku.toyooka.gu@hitachi.com>2012-12-26 11:52:52 +0900
committerSteven Rostedt <rostedt@goodmis.org>2013-01-30 11:02:05 -0500
commit2fd196ec1eab2623096e7fc7e6f3976160392bce (patch)
tree1994d70de20c1a1bc296e02d352142414484355b /kernel/trace
parent5e67b51e3fb22ad43faf9589e9019ad9c6a00413 (diff)
downloadop-kernel-dev-2fd196ec1eab2623096e7fc7e6f3976160392bce.zip
op-kernel-dev-2fd196ec1eab2623096e7fc7e6f3976160392bce.tar.gz
tracing: Replace static old_tracer check of tracer name
Currently the trace buffer read functions use a static variable "old_tracer" for detecting if the current tracer changes. This was suitable for a single trace file ("trace"), but to add a snapshot feature that will use the same function for its file, a check against a static variable is not sufficient. To use the output functions for two different files, instead of storing the current tracer in a static variable, as the trace iterator descriptor contains a pointer to the original current tracer's name, that pointer can now be used to check if the current tracer has changed between different reads of the trace file. Link: http://lkml.kernel.org/r/20121226025252.3252.9276.stgit@liselsia Signed-off-by: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.c22
1 files changed, 9 insertions, 13 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 90a1c71..2c72466 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,18 +1948,20 @@ void tracing_iter_reset(struct trace_iterator *iter, int cpu)
static void *s_start(struct seq_file *m, loff_t *pos)
{
struct trace_iterator *iter = m->private;
- static struct tracer *old_tracer;
int cpu_file = iter->cpu_file;
void *p = NULL;
loff_t l = 0;
int cpu;
- /* copy the tracer to avoid using a global lock all around */
+ /*
+ * copy the tracer to avoid using a global lock all around.
+ * iter->trace is a copy of current_trace, the pointer to the
+ * name may be used instead of a strcmp(), as iter->trace->name
+ * will point to the same string as current_trace->name.
+ */
mutex_lock(&trace_types_lock);
- if (unlikely(old_tracer != current_trace && current_trace)) {
- old_tracer = current_trace;
+ if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
- }
mutex_unlock(&trace_types_lock);
atomic_inc(&trace_record_cmdline_disabled);
@@ -3494,7 +3496,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
struct trace_iterator *iter = filp->private_data;
- static struct tracer *old_tracer;
ssize_t sret;
/* return any leftover data */
@@ -3506,10 +3507,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
/* copy the tracer to avoid using a global lock all around */
mutex_lock(&trace_types_lock);
- if (unlikely(old_tracer != current_trace && current_trace)) {
- old_tracer = current_trace;
+ if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
- }
mutex_unlock(&trace_types_lock);
/*
@@ -3665,7 +3664,6 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
.ops = &tracing_pipe_buf_ops,
.spd_release = tracing_spd_release_pipe,
};
- static struct tracer *old_tracer;
ssize_t ret;
size_t rem;
unsigned int i;
@@ -3675,10 +3673,8 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
/* copy the tracer to avoid using a global lock all around */
mutex_lock(&trace_types_lock);
- if (unlikely(old_tracer != current_trace && current_trace)) {
- old_tracer = current_trace;
+ if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
- }
mutex_unlock(&trace_types_lock);
mutex_lock(&iter->mutex);
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