MIPS: Add LATENCYTOP support

Add LATENCYTOP support for MIPS. Tested on OCTEON.
Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11353/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -2759,6 +2759,10 @@ config STACKTRACE_SUPPORT
 	bool
 	default y
 
+config HAVE_LATENCYTOP_SUPPORT
+	bool
+	default y
+
 config PGTABLE_LEVELS
 	int
 	default 3 if 64BIT && !PAGE_SIZE_64KB

arch/mips/kernel/stacktrace.c

@@ -12,14 +12,15 @@
  * Save stack-backtrace addresses into a stack_trace buffer:
  */
 static void save_raw_context_stack(struct stack_trace *trace,
-	unsigned long reg29)
+	unsigned long reg29, int savesched)
 {
 	unsigned long *sp = (unsigned long *)reg29;
 	unsigned long addr;
 
 	while (!kstack_end(sp)) {
 		addr = *sp++;
-		if (__kernel_text_address(addr)) {
+		if (__kernel_text_address(addr) &&
+		    (savesched || !in_sched_functions(addr))) {
 			if (trace->skip > 0)
 				trace->skip--;
 			else
@@ -31,7 +32,7 @@ static void save_raw_context_stack(struct stack_trace *trace,
 }
 
 static void save_context_stack(struct stack_trace *trace,
-	struct task_struct *tsk, struct pt_regs *regs)
+	struct task_struct *tsk, struct pt_regs *regs, int savesched)
 {
 	unsigned long sp = regs->regs[29];
 #ifdef CONFIG_KALLSYMS
@@ -43,20 +44,22 @@ static void save_context_stack(struct stack_trace *trace,
 			(unsigned long)task_stack_page(tsk);
 		if (stack_page && sp >= stack_page &&
 		    sp <= stack_page + THREAD_SIZE - 32)
-			save_raw_context_stack(trace, sp);
+			save_raw_context_stack(trace, sp, savesched);
 		return;
 	}
 	do {
+		if (savesched || !in_sched_functions(pc)) {
 			if (trace->skip > 0)
 				trace->skip--;
 			else
 				trace->entries[trace->nr_entries++] = pc;
 			if (trace->nr_entries >= trace->max_entries)
 				break;
+		}
 		pc = unwind_stack(tsk, &sp, pc, &ra);
 	} while (pc);
 #else
-	save_raw_context_stack(trace, sp);
+	save_raw_context_stack(trace, sp, savesched);
 #endif
 }
 
@@ -82,6 +85,6 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 		regs->cp0_epc = tsk->thread.reg31;
 	} else
 		prepare_frametrace(regs);
-	save_context_stack(trace, tsk, regs);
+	save_context_stack(trace, tsk, regs, tsk == current);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);