ARC: Fix thread_saved_pc()

The old implementation assumed that SP at the time of __switch_to() is
right above pt_regs which is almost certainly not the case as there will
be some stack build up between entry into kernel and leading up to
__switch_to
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/processor.h

@@ -47,9 +47,6 @@ struct thread_struct {
 /* Forward declaration, a strange C thing */
 struct task_struct;
 
-/* Return saved PC of a blocked thread  */
-unsigned long thread_saved_pc(struct task_struct *t);
-
 #define task_pt_regs(p) \
 	((struct pt_regs *)(THREAD_SIZE + (void *)task_stack_page(p)) - 1)
 
@@ -86,6 +83,8 @@ unsigned long thread_saved_pc(struct task_struct *t);
 #define TSK_K_BLINK(tsk)	TSK_K_REG(tsk, 4)
 #define TSK_K_FP(tsk)		TSK_K_REG(tsk, 0)
 
+#define thread_saved_pc(tsk)	TSK_K_BLINK(tsk)
+
 extern void start_thread(struct pt_regs * regs, unsigned long pc,
 			 unsigned long usp);
 

arch/arc/kernel/process.c

@@ -192,29 +192,6 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 	return 0;
 }
 
-/*
- * API: expected by schedular Code: If thread is sleeping where is that.
- * What is this good for? it will be always the scheduler or ret_from_fork.
- * So we hard code that anyways.
- */
-unsigned long thread_saved_pc(struct task_struct *t)
-{
-	struct pt_regs *regs = task_pt_regs(t);
-	unsigned long blink = 0;
-
-	/*
-	 * If the thread being queried for in not itself calling this, then it
-	 * implies it is not executing, which in turn implies it is sleeping,
-	 * which in turn implies it got switched OUT by the schedular.
-	 * In that case, it's kernel mode blink can reliably retrieved as per
-	 * the picture above (right above pt_regs).
-	 */
-	if (t != current && t->state != TASK_RUNNING)
-		blink = *((unsigned int *)regs - 1);
-
-	return blink;
-}
-
 int elf_check_arch(const struct elf32_hdr *x)
 {
 	unsigned int eflags;