init, tracing: Add initcall trace events

Being able to trace the start and stop of initcalls is useful to see where
the timings are an issue. There is already an "initcall_debug" parameter,
but that can cause a large overhead itself, as the printing of the
information may take longer than the initcall functions.

Adding in a start and finish trace event around the initcall functions, as
well as a trace event that records the level of the initcalls, one can get a
much finer measurement of the times and interactions of the initcalls
themselves, as trace events are much lighter than printk()s.

Suggested-by: Abderrahmane Benbachir <abderrahmane.benbachir@polymtl.ca>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/include/trace/events/initcall.h b/include/trace/events/initcall.h
new file mode 100644 (file)
index 0000000..8d6cf10
--- /dev/null
+++ b/include/trace/events/initcall.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM initcall
+
+#if !defined(_TRACE_INITCALL_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_INITCALL_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(initcall_level,
+
+       TP_PROTO(const char *level),
+
+       TP_ARGS(level),
+
+       TP_STRUCT__entry(
+               __string(level, level)
+       ),
+
+       TP_fast_assign(
+               __assign_str(level, level);
+       ),
+
+       TP_printk("level=%s", __get_str(level))
+);
+
+TRACE_EVENT(initcall_start,
+
+       TP_PROTO(initcall_t func),
+
+       TP_ARGS(func),
+
+       TP_STRUCT__entry(
+               __field(initcall_t, func)
+       ),
+
+       TP_fast_assign(
+               __entry->func = func;
+       ),
+
+       TP_printk("func=%pS", __entry->func)
+);
+
+TRACE_EVENT(initcall_finish,
+
+       TP_PROTO(initcall_t func, int ret),
+
+       TP_ARGS(func, ret),
+
+       TP_STRUCT__entry(
+               __field(initcall_t,     func)
+               __field(int,            ret)
+       ),
+
+       TP_fast_assign(
+               __entry->func = func;
+               __entry->ret = ret;
+       ),
+
+       TP_printk("func=%pS ret=%d", __entry->func, __entry->ret)
+);
+
+#endif /* if !defined(_TRACE_GPIO_H) || defined(TRACE_HEADER_MULTI_READ) */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

diff --git a/init/main.c b/init/main.c
index 0ebdd5f..2af8f2b 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -97,6 +97,9 @@
 #include <asm/sections.h>
 #include <asm/cacheflush.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/initcall.h>
+
 static int kernel_init(void *);
 
 extern void init_IRQ(void);
@@ -827,10 +830,12 @@ int __init_or_module do_one_initcall(initcall_t fn)
        if (initcall_blacklisted(fn))
                return -EPERM;
 
+       trace_initcall_start(fn);
        if (initcall_debug)
                ret = do_one_initcall_debug(fn);
        else
                ret = fn();
+       trace_initcall_finish(fn, ret);
 
        msgbuf[0] = 0;
 
@@ -895,6 +900,7 @@ static void __init do_initcall_level(int level)
                   level, level,
                   NULL, &repair_env_string);
 
+       trace_initcall_level(initcall_level_names[level]);
        for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)
                do_one_initcall(*fn);
 }
@@ -929,6 +935,7 @@ static void __init do_pre_smp_initcalls(void)
 {
        initcall_t *fn;
 
+       trace_initcall_level("early");
        for (fn = __initcall_start; fn < __initcall0_start; fn++)
                do_one_initcall(*fn);
 }