From 1d6d312d43a5cceda95705b3a04eb21a5c4cb310 Mon Sep 17 00:00:00 2001
From: Giovanni Di Sirio <gdisirio@gmail.com>
Date: Tue, 13 Nov 2018 10:36:05 +0000
Subject: 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 | 32 ++++++++++++++------------------
 os/common/ports/ARMCMx/chcore_v6m.h | 16 +++-------------
 2 files changed, 17 insertions(+), 31 deletions(-)

(limited to 'os/common/ports/ARMCMx')

diff --git a/os/common/ports/ARMCMx/chcore_v6m.c b/os/common/ports/ARMCMx/chcore_v6m.c
index 62daff813..5e43cb01a 100644
--- a/os/common/ports/ARMCMx/chcore_v6m.c
+++ b/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) {
-    struct port_extctx *ctxp;
+  port_lock_from_isr();
 
-    port_lock_from_isr();
-
-    /* The extctx structure is pointed by the PSP register.*/
-    ctxp = (struct port_extctx *)__get_PSP();
+  /* Checking if the artificial exception return context has already been
+     added.*/
+  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
-       required or not.*/
-    if (chSchIsPreemptionRequired()) {
-      /* 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;
-    }
+    /* Return address set to OS code, there context switch will be
+       performed.*/
+    ctxp->pc = (regarm_t)_port_switch_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();
 }
 
 /** @} */
diff --git a/os/common/ports/ARMCMx/chcore_v6m.h b/os/common/ports/ARMCMx/chcore_v6m.h
index d895f84a8..3d640506b 100644
--- a/os/common/ports/ARMCMx/chcore_v6m.h
+++ b/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()                                                 \
-  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
+#define PORT_IRQ_PROLOGUE()
 
 /**
  * @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
-- 
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