tracing: Kill unused and puzzled sample code in ftrace.h

#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)

/*

 * Define the insertion callback to perf events

 *

 * The job is very similar to ftrace_raw_event_<call> except that we don't

 * insert in the ring buffer but in a perf counter.

 *

 * static void ftrace_perf_<call>(proto)

 * {

 *	struct ftrace_data_offsets_<call> __maybe_unused __data_offsets;

 *	struct ftrace_event_call *event_call = &event_<call>;

 *	extern void perf_tp_event(int, u64, u64, void *, int);

 *	struct ftrace_raw_##call *entry;

 *	struct perf_trace_buf *trace_buf;

 *	u64 __addr = 0, __count = 1;

 *	unsigned long irq_flags;

 *	struct trace_entry *ent;

 *	int __entry_size;

 *	int __data_size;

 *	int __cpu

 *	int pc;

 *

 *	pc = preempt_count();

 *

 *	__data_size = ftrace_get_offsets_<call>(&__data_offsets, args);

 *

 *	// Below we want to get the aligned size by taking into account

 *	// the u32 field that will later store the buffer size

 *	__entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),

 *			     sizeof(u64));

 *	__entry_size -= sizeof(u32);

 *

 *	// Protect the non nmi buffer

 *	// This also protects the rcu read side

 *	local_irq_save(irq_flags);

 *	__cpu = smp_processor_id();

 *

 *	if (in_nmi())

 *		trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);

 *	else

 *		trace_buf = rcu_dereference_sched(perf_trace_buf);

 *

 *	if (!trace_buf)

 *		goto end;

 *

 *	trace_buf = per_cpu_ptr(trace_buf, __cpu);

 *

 * 	// Avoid recursion from perf that could mess up the buffer

 * 	if (trace_buf->recursion++)

 *		goto end_recursion;

 *

 * 	raw_data = trace_buf->buf;

 *

 *	// Make recursion update visible before entering perf_tp_event

 *	// so that we protect from perf recursions.

 *

 *	barrier();

 *

 *	//zero dead bytes from alignment to avoid stack leak to userspace:

 *	*(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;

 *	entry = (struct ftrace_raw_<call> *)raw_data;

 *	ent = &entry->ent;

 *	tracing_generic_entry_update(ent, irq_flags, pc);

 *	ent->type = event_call->id;

 *

 *	<tstruct> <- do some jobs with dynamic arrays

 *

 *	<assign>  <- affect our values

 *

 *	perf_tp_event(event_call->id, __addr, __count, entry,

 *		     __entry_size);  <- submit them to perf counter

 *

 * }

 */

#ifdef CONFIG_PERF_EVENTS