m68knommu: ColdFire add support for kernel preemption

As the subject says this patch adds the support for kernel preemption
on m68knommu Coldfire. I thing the same changes could be applied to
68360 & 68328 but since I don't have the HW for testing, I don't touch it.

Signed-off-by: Sebastian Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 17 insertions, 0 deletions

diff --git a/arch/m68knommu/kernel/asm-offsets.c b/arch/m68knommu/kernel/asm-offsets.c
index fd0c685a7f11..c785d07c02cc 100644
--- a/arch/m68knommu/kernel/asm-offsets.c
+++ b/arch/m68knommu/kernel/asm-offsets.c
@@ -87,6 +87,7 @@ int main(void)
         DEFINE(TI_TASK, offsetof(struct thread_info, task));
         DEFINE(TI_EXECDOMAIN, offsetof(struct thread_info, exec_domain));
         DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
+        DEFINE(TI_PREEMPTCOUNT, offsetof(struct thread_info, preempt_count));
         DEFINE(TI_CPU, offsetof(struct thread_info, cpu));
 
         return 0;
diff --git a/arch/m68knommu/platform/coldfire/entry.S b/arch/m68knommu/platform/coldfire/entry.S
index 111b66dc737b..1af7c1d650f6 100644
--- a/arch/m68knommu/platform/coldfire/entry.S
+++ b/arch/m68knommu/platform/coldfire/entry.S
@@ -106,6 +106,22 @@ ret_from_exception:
         btst    #5,%sp@(PT_SR)          /* check if returning to kernel */
         jeq     Luser_return            /* if so, skip resched, signals */
 
+#ifdef CONFIG_PREEMPT
+        movel   %sp,%d1                 /* get thread_info pointer */
+        andl    #-THREAD_SIZE,%d1       /* at base of kernel stack */
+        movel   %d1,%a0
+        movel   %a0@(TI_FLAGS),%d1      /* get thread_info->flags */
+        andl    #_TIF_NEED_RESCHED,%d1
+        jeq     Lkernel_return
+
+        movel   %a0@(TI_PREEMPTCOUNT),%d1
+        cmpl    #0,%d1
+        jne     Lkernel_return
+
+        pea     Lkernel_return
+        jmp     preempt_schedule_irq    /* preempt the kernel */
+#endif
+
 Lkernel_return:
         moveml  %sp@,%d1-%d5/%a0-%a2
         lea     %sp@(32),%sp            /* space for 8 regs */