tracing/function-graph-tracer: append the tracing_graph_flag
Impact: Provide a way to pause the function graph tracer
As suggested by Steven Rostedt, the previous patch that prevented from
spinlock function tracing shouldn't use the raw_spinlock to fix it.
It's much better to follow lockdep with normal spinlock, so this patch
adds a new flag for each task to make the function graph tracer able
to be paused. We also can send an ftrace_printk whithout worrying of
the irrelevant traced spinlock during insertion.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 2971fe4..a12f80e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1998,6 +1998,7 @@
/* Make sure IRQs see the -1 first: */
barrier();
t->ret_stack = ret_stack_list[start++];
+ atomic_set(&t->tracing_graph_pause, 0);
atomic_set(&t->trace_overrun, 0);
}
} while_each_thread(g, t);
@@ -2077,6 +2078,7 @@
if (!t->ret_stack)
return;
t->curr_ret_stack = -1;
+ atomic_set(&t->tracing_graph_pause, 0);
atomic_set(&t->trace_overrun, 0);
} else
t->ret_stack = NULL;
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3354953..0b8659b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3590,14 +3590,7 @@
int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
{
- /*
- * Raw Spinlock because a normal spinlock would be traced here
- * and append an irrelevant couple spin_lock_irqsave/
- * spin_unlock_irqrestore traced by ftrace around this
- * TRACE_PRINTK trace.
- */
- static raw_spinlock_t trace_buf_lock =
- (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+ static DEFINE_SPINLOCK(trace_buf_lock);
static char trace_buf[TRACE_BUF_SIZE];
struct ring_buffer_event *event;
@@ -3618,8 +3611,8 @@
if (unlikely(atomic_read(&data->disabled)))
goto out;
- local_irq_save(flags);
- __raw_spin_lock(&trace_buf_lock);
+ pause_graph_tracing();
+ spin_lock_irqsave(&trace_buf_lock, irq_flags);
len = vsnprintf(trace_buf, TRACE_BUF_SIZE, fmt, args);
len = min(len, TRACE_BUF_SIZE-1);
@@ -3640,9 +3633,8 @@
ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
out_unlock:
- __raw_spin_unlock(&trace_buf_lock);
- local_irq_restore(flags);
-
+ spin_unlock_irqrestore(&trace_buf_lock, irq_flags);
+ unpause_graph_tracing();
out:
preempt_enable_notrace();