tracing: Enable comm recording if trace_printk() is used
If comm recording is not enabled when trace_printk() is used then
you just get this type of output:
[ adding trace_printk("hello! %d", irq); in do_IRQ ]
<...>-2843 [001] d.h. 80.812300: do_IRQ: hello! 14
<...>-2734 [002] d.h2 80.824664: do_IRQ: hello! 14
<...>-2713 [003] d.h. 80.829971: do_IRQ: hello! 14
<...>-2814 [000] d.h. 80.833026: do_IRQ: hello! 14
By enabling the comm recorder when trace_printk is enabled:
hackbench-6715 [001] d.h. 193.233776: do_IRQ: hello! 21
sshd-2659 [001] d.h. 193.665862: do_IRQ: hello! 21
<idle>-0 [001] d.h1 193.665996: do_IRQ: hello! 21
Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a5411b7..b90a827 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1559,10 +1559,10 @@
return -ENOMEM;
}
+static int buffers_allocated;
+
void trace_printk_init_buffers(void)
{
- static int buffers_allocated;
-
if (buffers_allocated)
return;
@@ -1575,6 +1575,34 @@
tracing_update_buffers();
buffers_allocated = 1;
+
+ /*
+ * trace_printk_init_buffers() can be called by modules.
+ * If that happens, then we need to start cmdline recording
+ * directly here. If the global_trace.buffer is already
+ * allocated here, then this was called by module code.
+ */
+ if (global_trace.buffer)
+ tracing_start_cmdline_record();
+}
+
+void trace_printk_start_comm(void)
+{
+ /* Start tracing comms if trace printk is set */
+ if (!buffers_allocated)
+ return;
+ tracing_start_cmdline_record();
+}
+
+static void trace_printk_start_stop_comm(int enabled)
+{
+ if (!buffers_allocated)
+ return;
+
+ if (enabled)
+ tracing_start_cmdline_record();
+ else
+ tracing_stop_cmdline_record();
}
/**
@@ -2797,6 +2825,9 @@
if (mask == TRACE_ITER_OVERWRITE)
ring_buffer_change_overwrite(global_trace.buffer, enabled);
+
+ if (mask == TRACE_ITER_PRINTK)
+ trace_printk_start_stop_comm(enabled);
}
static ssize_t
@@ -5099,6 +5130,7 @@
/* Only allocate trace_printk buffers if a trace_printk exists */
if (__stop___trace_bprintk_fmt != __start___trace_bprintk_fmt)
+ /* Must be called before global_trace.buffer is allocated */
trace_printk_init_buffers();
/* To save memory, keep the ring buffer size to its minimum */