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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2013-02-01 18:38:47 -0500
committerSteven Rostedt <rostedt@goodmis.org>2013-02-01 18:38:47 -0500
commitd840f718d28715a9833c1a8f46c2493ff3fd219b (patch)
tree6fb0115db3dabd5ce79563fb1412c98edc24088e /kernel/trace
parentc1043fcda1b9e8e5144cfdaee7be262c50dbdead (diff)
tracing: Init current_trace to nop_trace and remove NULL checks
On early boot up, when the ftrace ring buffer is initialized, the static variable current_trace is initialized to &nop_trace. Before this initialization, current_trace is NULL and will never become NULL again. It is always reassigned to a ftrace tracer. Several places check if current_trace is NULL before it uses it, and this check is frivolous, because at the point in time when the checks are made the only way current_trace could be NULL is if ftrace failed its allocations at boot up, and the paths to these locations would probably not be possible. By initializing current_trace to &nop_trace where it is declared, current_trace will never be NULL, and we can remove all these checks of current_trace being NULL which never needed to be checked in the first place. Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: 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.c30
1 files changed, 12 insertions, 18 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 70dce64b9ecf..5d520b7bb4c5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -249,7 +249,7 @@ static unsigned long trace_buf_size = TRACE_BUF_SIZE_DEFAULT;
static struct tracer *trace_types __read_mostly;
/* current_trace points to the tracer that is currently active */
-static struct tracer *current_trace __read_mostly;
+static struct tracer *current_trace __read_mostly = &nop_trace;
/*
* trace_types_lock is used to protect the trace_types list.
@@ -2100,8 +2100,7 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
unsigned long total;
const char *name = "preemption";
- if (type)
- name = type->name;
+ name = type->name;
get_total_entries(tr, &total, &entries);
@@ -2477,13 +2476,12 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
if (!iter->trace)
goto fail;
- if (current_trace)
- *iter->trace = *current_trace;
+ *iter->trace = *current_trace;
if (!zalloc_cpumask_var(&iter->started, GFP_KERNEL))
goto fail;
- if ((current_trace && current_trace->print_max) || snapshot)
+ if (current_trace->print_max || snapshot)
iter->tr = &max_tr;
else
iter->tr = &global_trace;
@@ -3037,10 +3035,7 @@ tracing_set_trace_read(struct file *filp, char __user *ubuf,
int r;
mutex_lock(&trace_types_lock);
- if (current_trace)
- r = sprintf(buf, "%s\n", current_trace->name);
- else
- r = sprintf(buf, "\n");
+ r = sprintf(buf, "%s\n", current_trace->name);
mutex_unlock(&trace_types_lock);
return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
@@ -3231,10 +3226,10 @@ static int tracing_set_tracer(const char *buf)
goto out;
trace_branch_disable();
- if (current_trace && current_trace->reset)
+ if (current_trace->reset)
current_trace->reset(tr);
- had_max_tr = current_trace && current_trace->allocated_snapshot;
+ had_max_tr = current_trace->allocated_snapshot;
current_trace = &nop_trace;
if (had_max_tr && !t->use_max_tr) {
@@ -3373,8 +3368,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
ret = -ENOMEM;
goto fail;
}
- if (current_trace)
- *iter->trace = *current_trace;
+ *iter->trace = *current_trace;
if (!alloc_cpumask_var(&iter->started, GFP_KERNEL)) {
ret = -ENOMEM;
@@ -3525,7 +3519,7 @@ 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(current_trace && iter->trace->name != current_trace->name))
+ if (unlikely(iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
mutex_unlock(&trace_types_lock);
@@ -3691,7 +3685,7 @@ 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(current_trace && iter->trace->name != current_trace->name))
+ if (unlikely(iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
mutex_unlock(&trace_types_lock);
@@ -4115,7 +4109,7 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
mutex_lock(&trace_types_lock);
- if (current_trace && current_trace->use_max_tr) {
+ if (current_trace->use_max_tr) {
ret = -EBUSY;
goto out;
}
@@ -5299,7 +5293,7 @@ __init static int tracer_alloc_buffers(void)
init_irq_work(&trace_work_wakeup, trace_wake_up);
register_tracer(&nop_trace);
- current_trace = &nop_trace;
+
/* All seems OK, enable tracing */
tracing_disabled = 0;