[IA64] Only unwind non-running tasks.

Unwinding a running task has proven problematic.

In one instance, the running task was attempting to unwind itself and
received an interrupt between when get_wchan allocated local variables on
the stack and when unw_init_from_blocked_task was called which resulted
in unw_init_frame_info to place this tasks task_struct pointer over the
switch stack's ar_bspstore entry.

Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index d1c3ed9943e5..af73b8dfde28 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -763,6 +763,9 @@ get_wchan (struct task_struct *p)
         unsigned long ip;
         int count = 0;
 
+        if (!p || p == current || p->state == TASK_RUNNING)
+                return 0;
+
         /*
          * Note: p may not be a blocked task (it could be current or
          * another process running on some other CPU.  Rather than
@@ -773,6 +776,8 @@ get_wchan (struct task_struct *p)
          */
         unw_init_from_blocked_task(&info, p);
         do {
+                if (p->state == TASK_RUNNING)
+                        return 0;
                 if (unw_unwind(&info) < 0)
                         return 0;
                 unw_get_ip(&info, &ip);