[PARISC] be more defensive in process.c::get_wchan

While debugging, I noticed we don't check the task_struct arg passed to
get_wchan, whereas everyone else does.

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 0dd3847f494c..355664812b83 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -381,6 +381,10 @@ get_wchan(struct task_struct *p)
         struct unwind_frame_info info;
         unsigned long ip;
         int count = 0;
+
+        if (!p || p == current || p->state == TASK_RUNNING)
+                return 0;
+
         /*
          * These bracket the sleeping functions..
          */