nmi_backtrace: generate one-line reports for idle cpus

[cascardo/linux.git] / arch / x86 / kernel / process.c

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 0b9ed8e..28cea78 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -302,7 +302,7 @@ void arch_cpu_idle(void)
 /*
  * We use this if we don't have any better idle routine..
  */
-void default_idle(void)
+void __cpuidle default_idle(void)
 {
        trace_cpu_idle_rcuidle(1, smp_processor_id());
        safe_halt();
@@ -417,7 +417,7 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
  * with interrupts enabled and no flags, which is backwards compatible with the
  * original MWAIT implementation.
  */
-static void mwait_idle(void)
+static __cpuidle void mwait_idle(void)
 {
        if (!current_set_polling_and_test()) {
                trace_cpu_idle_rcuidle(1, smp_processor_id());
@@ -532,15 +532,18 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
  */
 unsigned long get_wchan(struct task_struct *p)
 {
-       unsigned long start, bottom, top, sp, fp, ip;
+       unsigned long start, bottom, top, sp, fp, ip, ret = 0;
        int count = 0;
 
        if (!p || p == current || p->state == TASK_RUNNING)
                return 0;
 
+       if (!try_get_task_stack(p))
+               return 0;
+
        start = (unsigned long)task_stack_page(p);
        if (!start)
-               return 0;
+               goto out;
 
        /*
         * Layout of the stack page:
@@ -564,16 +567,21 @@ unsigned long get_wchan(struct task_struct *p)
 
        sp = READ_ONCE(p->thread.sp);
        if (sp < bottom || sp > top)
-               return 0;
+               goto out;
 
        fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
        do {
                if (fp < bottom || fp > top)
-                       return 0;
+                       goto out;
                ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
-               if (!in_sched_functions(ip))
-                       return ip;
+               if (!in_sched_functions(ip)) {
+                       ret = ip;
+                       goto out;
+               }
                fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
        } while (count++ < 16 && p->state != TASK_RUNNING);
-       return 0;
+
+out:
+       put_task_stack(p);
+       return ret;
 }