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tracing: Move enabling tracepoints to just after rcu_init()

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Enabling tracepoints at boot up can be very useful. The tracepoint
can be initialized right after RCU has been. There's no need to
wait for the early_initcall() to be called. That's too late for some
things that can use tracepoints for debugging. Move the logic to
enable tracepoints out of the initcalls and into init/main.c to
right after rcu_init().

This also allows trace_printk() to be used early too.

Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1412121539300.16494@nanos
Link: http://lkml.kernel.org/r/20141214164104.307127356@goodmis.org

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2014-12-12 20:05:10 -05:00 committed by Steven Rostedt
parent aee4e5f3d3
commit 5f893b2639
6 changed files with 40 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
include/linux/ftrace.h
View file

@ -39,6 +39,12 @@
# define FTRACE_FORCE_LIST_FUNC 0
#endif
/* Main tracing buffer and events set up */
#ifdef CONFIG_TRACING
void trace_init(void);
#else
static inline void trace_init(void) { }
#endif
struct module;
struct ftrace_hash;

4
init/main.c
View file

@ -577,6 +577,10 @@ asmlinkage __visible void __init start_kernel(void)
local_irq_disable();
idr_init_cache();
rcu_init();
/* trace_printk() and trace points may be used after this */
trace_init();
context_tracking_init();
radix_tree_init();
/* init some links before init_ISA_irqs() */

8
kernel/trace/trace.c
View file

@ -6876,6 +6876,13 @@ __init static int tracer_alloc_buffers(void)
return ret;
}
void __init trace_init(void)
{
tracer_alloc_buffers();
init_ftrace_syscalls();
trace_event_init();
}
__init static int clear_boot_tracer(void)
{
/*
@ -6895,6 +6902,5 @@ __init static int clear_boot_tracer(void)
return 0;
}
early_initcall(tracer_alloc_buffers);
fs_initcall(tracer_init_debugfs);
late_initcall(clear_boot_tracer);

13
kernel/trace/trace.h
View file

@ -1301,4 +1301,17 @@ int perf_ftrace_event_register(struct ftrace_event_call *call,
#define perf_ftrace_event_register NULL
#endif
#ifdef CONFIG_FTRACE_SYSCALLS
void init_ftrace_syscalls(void);
#else
static inline void init_ftrace_syscalls(void) { }
#endif
#ifdef CONFIG_EVENT_TRACING
void trace_event_init(void);
#else
static inline void __init trace_event_init(void) { }
#endif
#endif /* _LINUX_KERNEL_TRACE_H */

10
kernel/trace/trace_events.c
View file

@ -2477,8 +2477,14 @@ static __init int event_trace_init(void)
#endif
return 0;
}
early_initcall(event_trace_memsetup);
core_initcall(event_trace_enable);
void __init trace_event_init(void)
{
event_trace_memsetup();
init_ftrace_syscalls();
event_trace_enable();
}
fs_initcall(event_trace_init);
#ifdef CONFIG_FTRACE_STARTUP_TEST

7
kernel/trace/trace_syscalls.c
View file

@ -514,7 +514,7 @@ unsigned long __init __weak arch_syscall_addr(int nr)
return (unsigned long)sys_call_table[nr];
}
static int __init init_ftrace_syscalls(void)
void __init init_ftrace_syscalls(void)
{
struct syscall_metadata *meta;
unsigned long addr;
@ -524,7 +524,7 @@ static int __init init_ftrace_syscalls(void)
GFP_KERNEL);
if (!syscalls_metadata) {
WARN_ON(1);
return -ENOMEM;
return;
}
for (i = 0; i < NR_syscalls; i++) {
@ -536,10 +536,7 @@ static int __init init_ftrace_syscalls(void)
meta->syscall_nr = i;
syscalls_metadata[i] = meta;
}
return 0;
}
early_initcall(init_ftrace_syscalls);
#ifdef CONFIG_PERF_EVENTS