Tentative fix for bug #985.

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@12416 110e8d01-0319-4d1e-a829-52ad28d1bb01

os/common/ports/ARMCMx/chcore_v6m.c

@@ -107,15 +107,16 @@ void PendSV_Handler(void) {
  *
  * @param[in] lr        value of the @p LR register on ISR entry
  */
-void _port_irq_epilogue(regarm_t lr) {
+void _port_irq_epilogue(void) {
+  struct port_extctx *ctxp;
 
-  if (lr != (regarm_t)0xFFFFFFF1U) {
+  port_lock_from_isr();
-    struct port_extctx *ctxp;
 
-    port_lock_from_isr();
+  /* Checking if the artificial exception return context has already been
-
+     added.*/
-    /* The extctx structure is pointed by the PSP register.*/
+  ctxp = (struct port_extctx *)__get_PSP();
-    ctxp = (struct port_extctx *)__get_PSP();
+  if ((ctxp->pc != (regarm_t)_port_switch_from_isr) &&
+      chSchIsPreemptionRequired()) {
 
     /* Adding an artificial exception return context, there is no need to
        populate it fully.*/
@@ -127,21 +128,16 @@ void _port_irq_epilogue(regarm_t lr) {
     /* Setting up a fake XPSR register value.*/
     ctxp->xpsr = (regarm_t)0x01000000;
 
-    /* The exit sequence is different depending on if a preemption is
+    /* Return address set to OS code, there context switch will be
-       required or not.*/
+       performed.*/
-    if (chSchIsPreemptionRequired()) {
+    ctxp->pc = (regarm_t)_port_switch_from_isr;
-      /* Preemption is required we need to enforce a context switch.*/
-      ctxp->pc = (regarm_t)_port_switch_from_isr;
-    }
-    else {
-      /* Preemption not required, we just need to exit the exception
-         atomically.*/
-      ctxp->pc = (regarm_t)_port_exit_from_isr;
-    }
 
     /* Note, returning without unlocking is intentional, this is done in
        order to keep the rest of the context switch atomic.*/
+    return;
   }
+
+  port_unlock_from_isr();
 }
 
 /** @} */

os/common/ports/ARMCMx/chcore_v6m.h

@@ -246,23 +246,14 @@ struct port_intctx {
  * @details This macro must be inserted at the start of all IRQ handlers
  *          enabled to invoke system APIs.
  */
-#if defined(__GNUC__) || defined(__DOXYGEN__)
+#define PORT_IRQ_PROLOGUE()
-#define PORT_IRQ_PROLOGUE()                                                 \
-  regarm_t _saved_lr = (regarm_t)__builtin_return_address(0)
-#elif defined(__ICCARM__)
-#define PORT_IRQ_PROLOGUE()                                                 \
-  regarm_t _saved_lr = (regarm_t)__get_LR()
-#elif defined(__CC_ARM)
-#define PORT_IRQ_PROLOGUE()                                                 \
-  regarm_t _saved_lr = (regarm_t)__return_address()
-#endif
 
 /**
  * @brief   IRQ epilogue code.
  * @details This macro must be inserted at the end of all IRQ handlers
  *          enabled to invoke system APIs.
  */
-#define PORT_IRQ_EPILOGUE() _port_irq_epilogue(_saved_lr)
+#define PORT_IRQ_EPILOGUE() _port_irq_epilogue()
 
 /**
  * @brief   IRQ handler function declaration.
@@ -307,11 +298,10 @@ struct port_intctx {
 #ifdef __cplusplus
 extern "C" {
 #endif
-  void _port_irq_epilogue(regarm_t lr);
+  void _port_irq_epilogue(void);
   void _port_switch(thread_t *ntp, thread_t *otp);
   void _port_thread_start(void);
   void _port_switch_from_isr(void);
-  void _port_exit_from_isr(void);
 #ifdef __cplusplus
 }
 #endif

readme.txt

@@ -160,6 +160,7 @@
 - EX:  Updated LIS302DL to 1.1.0 (backported to 18.2.1).
 - EX:  Updated LPS25H to 1.1.0 (backported to 18.2.1).
 - EX:  Updated LSM303DLHC to 1.1.0 (backported to 18.2.1).
+- RT:  Fixed GCC6 problem breaks Cortex-M0 port (bug #985).
 - NIL: Fixed scheduler misbehaving in rare cases (bug #983)
        (backported to 18.2.2 and 17.6.5).
 - NIL: Fixed function chThdSuspendTimeoutS() ignoring TIME_IMMEDIATE (bug #982)