ftrace: Reverse what the RECURSION flag means in the ftrace_ops

Now that all callbacks are recursion safe, reverse the meaning of the
RECURSION flag and rename it from RECURSION_SAFE to simply RECURSION.
Now only callbacks that request to have recursion protecting it will
have the added trampoline to do so.

Also remove the outdated comment about "PER_CPU" when determining to
use the ftrace_ops_assist_func.

Link: https://lkml.kernel.org/r/20201028115613.742454631@goodmis.org
Link: https://lkml.kernel.org/r/20201106023547.904270143@goodmis.org

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh  Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 9 insertions, 11 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8185f7240095..39f2bba89b76 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -80,7 +80,7 @@ enum {
 
 struct ftrace_ops ftrace_list_end __read_mostly = {
 	.func		= ftrace_stub,
-	.flags		= FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_STUB,
+	.flags		= FTRACE_OPS_FL_STUB,
 	INIT_OPS_HASH(ftrace_list_end)
 };
 
@@ -866,7 +866,7 @@ static void unregister_ftrace_profiler(void)
 #else
 static struct ftrace_ops ftrace_profile_ops __read_mostly = {
 	.func		= function_profile_call,
-	.flags		= FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
+	.flags		= FTRACE_OPS_FL_INITIALIZED,
 	INIT_OPS_HASH(ftrace_profile_ops)
 };
 
@@ -1040,8 +1040,7 @@ struct ftrace_ops global_ops = {
 	.local_hash.notrace_hash	= EMPTY_HASH,
 	.local_hash.filter_hash		= EMPTY_HASH,
 	INIT_OPS_HASH(global_ops)
-	.flags				= FTRACE_OPS_FL_RECURSION_SAFE |
-					  FTRACE_OPS_FL_INITIALIZED |
+	.flags				= FTRACE_OPS_FL_INITIALIZED |
 					  FTRACE_OPS_FL_PID,
 };
 
@@ -2382,7 +2381,7 @@ static void call_direct_funcs(unsigned long ip, unsigned long pip,
 
 struct ftrace_ops direct_ops = {
 	.func		= call_direct_funcs,
-	.flags		= FTRACE_OPS_FL_IPMODIFY | FTRACE_OPS_FL_RECURSION_SAFE
+	.flags		= FTRACE_OPS_FL_IPMODIFY
 			  | FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS
 			  | FTRACE_OPS_FL_PERMANENT,
 	/*
@@ -6864,8 +6863,7 @@ void ftrace_init_trace_array(struct trace_array *tr)
 
 struct ftrace_ops global_ops = {
 	.func			= ftrace_stub,
-	.flags			= FTRACE_OPS_FL_RECURSION_SAFE |
-				  FTRACE_OPS_FL_INITIALIZED |
+	.flags			= FTRACE_OPS_FL_INITIALIZED |
 				  FTRACE_OPS_FL_PID,
 };
 
@@ -7023,11 +7021,11 @@ NOKPROBE_SYMBOL(ftrace_ops_assist_func);
 ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops)
 {
 	/*
-	 * If the function does not handle recursion, needs to be RCU safe,
-	 * or does per cpu logic, then we need to call the assist handler.
+	 * If the function does not handle recursion or needs to be RCU safe,
+	 * then we need to call the assist handler.
 	 */
-	if (!(ops->flags & FTRACE_OPS_FL_RECURSION_SAFE) ||
-	    ops->flags & FTRACE_OPS_FL_RCU)
+	if (ops->flags & (FTRACE_OPS_FL_RECURSION |
+			  FTRACE_OPS_FL_RCU))
 		return ftrace_ops_assist_func;
 
 	return ops->func;