[PATCH 3/3] ftrace: Kill FTRACE_OPS_FL_PER_CPU

[Peter Zijlstra]

The one and only user of FTRACE_OPS_FL_PER_CPU is gone, remove the
lot.


Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 include/linux/ftrace.h |   57 +------------------------------------------------
 kernel/trace/ftrace.c  |   55 +++++------------------------------------------
 2 files changed, 8 insertions(+), 104 deletions(-)

--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -78,10 +78,7 @@ ftrace_func_t ftrace_ops_get_func(struct
  * ENABLED - set/unset when ftrace_ops is registered/unregistered
  * DYNAMIC - set when ftrace_ops is registered to denote dynamically
  *           allocated ftrace_ops which need special care
- * PER_CPU - set manualy by ftrace_ops user to denote the ftrace_ops
- *           could be controlled by following calls:
- *             ftrace_function_local_enable
- *             ftrace_function_local_disable
+ *
  * SAVE_REGS - The ftrace_ops wants regs saved at each function called
  *            and passed to the callback. If this flag is set, but the
  *            architecture does not support passing regs
@@ -125,7 +122,7 @@ ftrace_func_t ftrace_ops_get_func(struct
 enum {
 	FTRACE_OPS_FL_ENABLED			= 1 << 0,
 	FTRACE_OPS_FL_DYNAMIC			= 1 << 1,
-	FTRACE_OPS_FL_PER_CPU			= 1 << 2,
+
 	FTRACE_OPS_FL_SAVE_REGS			= 1 << 3,
 	FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED	= 1 << 4,
 	FTRACE_OPS_FL_RECURSION_SAFE		= 1 << 5,
@@ -172,7 +169,6 @@ struct ftrace_ops {
 	unsigned long			flags;
 	void				*private;
 	ftrace_func_t			saved_func;
-	int __percpu			*disabled;
 #ifdef CONFIG_DYNAMIC_FTRACE
 	struct ftrace_ops_hash		local_hash;
 	struct ftrace_ops_hash		*func_hash;
@@ -204,55 +200,6 @@ int register_ftrace_function(struct ftra
 int unregister_ftrace_function(struct ftrace_ops *ops);
 void clear_ftrace_function(void);
 
-/**
- * ftrace_function_local_enable - enable ftrace_ops on current cpu
- *
- * This function enables tracing on current cpu by decreasing
- * the per cpu control variable.
- * It must be called with preemption disabled and only on ftrace_ops
- * registered with FTRACE_OPS_FL_PER_CPU. If called without preemption
- * disabled, this_cpu_ptr will complain when CONFIG_DEBUG_PREEMPT is enabled.
- */
-static inline void ftrace_function_local_enable(struct ftrace_ops *ops)
-{
-	if (WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_PER_CPU)))
-		return;
-
-	(*this_cpu_ptr(ops->disabled))--;
-}
-
-/**
- * ftrace_function_local_disable - disable ftrace_ops on current cpu
- *
- * This function disables tracing on current cpu by increasing
- * the per cpu control variable.
- * It must be called with preemption disabled and only on ftrace_ops
- * registered with FTRACE_OPS_FL_PER_CPU. If called without preemption
- * disabled, this_cpu_ptr will complain when CONFIG_DEBUG_PREEMPT is enabled.
- */
-static inline void ftrace_function_local_disable(struct ftrace_ops *ops)
-{
-	if (WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_PER_CPU)))
-		return;
-
-	(*this_cpu_ptr(ops->disabled))++;
-}
-
-/**
- * ftrace_function_local_disabled - returns ftrace_ops disabled value
- *                                  on current cpu
- *
- * This function returns value of ftrace_ops::disabled on current cpu.
- * It must be called with preemption disabled and only on ftrace_ops
- * registered with FTRACE_OPS_FL_PER_CPU. If called without preemption
- * disabled, this_cpu_ptr will complain when CONFIG_DEBUG_PREEMPT is enabled.
- */
-static inline int ftrace_function_local_disabled(struct ftrace_ops *ops)
-{
-	WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_PER_CPU));
-	return *this_cpu_ptr(ops->disabled);
-}
-
 extern void ftrace_stub(unsigned long a0, unsigned long a1,
 			struct ftrace_ops *op, struct pt_regs *regs);
 
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -203,30 +203,6 @@ void clear_ftrace_function(void)
 	ftrace_trace_function = ftrace_stub;
 }
 
-static void per_cpu_ops_disable_all(struct ftrace_ops *ops)
-{
-	int cpu;
-
-	for_each_possible_cpu(cpu)
-		*per_cpu_ptr(ops->disabled, cpu) = 1;
-}
-
-static int per_cpu_ops_alloc(struct ftrace_ops *ops)
-{
-	int __percpu *disabled;
-
-	if (WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_PER_CPU)))
-		return -EINVAL;
-
-	disabled = alloc_percpu(int);
-	if (!disabled)
-		return -ENOMEM;
-
-	ops->disabled = disabled;
-	per_cpu_ops_disable_all(ops);
-	return 0;
-}
-
 static void ftrace_sync(struct work_struct *work)
 {
 	/*
@@ -262,8 +238,8 @@ static ftrace_func_t ftrace_ops_get_list
 	 * If this is a dynamic, RCU, or per CPU ops, or we force list func,
 	 * then it needs to call the list anyway.
 	 */
-	if (ops->flags & (FTRACE_OPS_FL_DYNAMIC | FTRACE_OPS_FL_PER_CPU |
-			  FTRACE_OPS_FL_RCU) || FTRACE_FORCE_LIST_FUNC)
+	if (ops->flags & (FTRACE_OPS_FL_DYNAMIC | FTRACE_OPS_FL_RCU) ||
+	    FTRACE_FORCE_LIST_FUNC)
 		return ftrace_ops_list_func;
 
 	return ftrace_ops_get_func(ops);
@@ -422,11 +398,6 @@ static int __register_ftrace_function(st
 	if (!core_kernel_data((unsigned long)ops))
 		ops->flags |= FTRACE_OPS_FL_DYNAMIC;
 
-	if (ops->flags & FTRACE_OPS_FL_PER_CPU) {
-		if (per_cpu_ops_alloc(ops))
-			return -ENOMEM;
-	}
-
 	add_ftrace_ops(&ftrace_ops_list, ops);
 
 	/* Always save the function, and reset at unregistering */
@@ -2727,11 +2698,6 @@ void __weak arch_ftrace_trampoline_free(
 {
 }
 
-static void per_cpu_ops_free(struct ftrace_ops *ops)
-{
-	free_percpu(ops->disabled);
-}
-
 static void ftrace_startup_enable(int command)
 {
 	if (saved_ftrace_func != ftrace_trace_function) {
@@ -2833,7 +2799,7 @@ static int ftrace_shutdown(struct ftrace
 		 * not currently active, we can just free them
 		 * without synchronizing all CPUs.
 		 */
-		if (ops->flags & (FTRACE_OPS_FL_DYNAMIC | FTRACE_OPS_FL_PER_CPU))
+		if (ops->flags & FTRACE_OPS_FL_DYNAMIC)
 			goto free_ops;
 
 		return 0;
@@ -2880,7 +2846,7 @@ static int ftrace_shutdown(struct ftrace
 	 * The same goes for freeing the per_cpu data of the per_cpu
 	 * ops.
 	 */
-	if (ops->flags & (FTRACE_OPS_FL_DYNAMIC | FTRACE_OPS_FL_PER_CPU)) {
+	if (ops->flags & (FTRACE_OPS_FL_DYNAMIC)) {
 		/*
 		 * We need to do a hard force of sched synchronization.
 		 * This is because we use preempt_disable() to do RCU, but
@@ -2903,9 +2869,6 @@ static int ftrace_shutdown(struct ftrace
 
  free_ops:
 		arch_ftrace_trampoline_free(ops);
-
-		if (ops->flags & FTRACE_OPS_FL_PER_CPU)
-			per_cpu_ops_free(ops);
 	}
 
 	return 0;
@@ -6066,10 +6029,7 @@ __ftrace_ops_list_func(unsigned long ip,
 		 * If any of the above fails then the op->func() is not executed.
 		 */
 		if ((!(op->flags & FTRACE_OPS_FL_RCU) || rcu_is_watching()) &&
-		    (!(op->flags & FTRACE_OPS_FL_PER_CPU) ||
-		     !ftrace_function_local_disabled(op)) &&
 		    ftrace_ops_test(op, ip, regs)) {
-		    
 			if (FTRACE_WARN_ON(!op->func)) {
 				pr_warn("op=%p %pS\n", op, op);
 				goto out;
@@ -6127,10 +6087,7 @@ static void ftrace_ops_assist_func(unsig
 
 	preempt_disable_notrace();
 
-	if (!(op->flags & FTRACE_OPS_FL_PER_CPU) ||
-	    !ftrace_function_local_disabled(op)) {
-		op->func(ip, parent_ip, op, regs);
-	}
+	op->func(ip, parent_ip, op, regs);
 
 	preempt_enable_notrace();
 	trace_clear_recursion(bit);
@@ -6154,7 +6111,7 @@ ftrace_func_t ftrace_ops_get_func(struct
 	 * or does per cpu logic, then we need to call the assist handler.
 	 */
 	if (!(ops->flags & FTRACE_OPS_FL_RECURSION_SAFE) ||
-	    ops->flags & (FTRACE_OPS_FL_RCU | FTRACE_OPS_FL_PER_CPU))
+	    ops->flags & FTRACE_OPS_FL_RCU)
 		return ftrace_ops_assist_func;
 
 	return ops->func;