Improved certain Cortex-M3 context switch times

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2177 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 178 insertions, 0 deletions

diff --git a/nuttx/arch/arm/src/cortexm3/up_reprioritizertr.c b/nuttx/arch/arm/src/cortexm3/up_reprioritizertr.c
new file mode 100755
index 000000000..4d406de80
--- /dev/null
+++ b/nuttx/arch/arm/src/cortexm3/up_reprioritizertr.c
@@ -0,0 +1,178 @@
+/****************************************************************************
+ *  arch/arm/src/cortexm3/up_reprioritizertr.c
+ *
+ *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <sched.h>
+#include <debug.h>
+#include <nuttx/arch.h>
+#include "os_internal.h"
+#include "up_internal.h"
+
+/****************************************************************************
+ * Private Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: up_reprioritize_rtr
+ *
+ * Description:
+ *   Called when the priority of a running or
+ *   ready-to-run task changes and the reprioritization will 
+ *   cause a context switch.  Two cases:
+ *
+ *   1) The priority of the currently running task drops and the next
+ *      task in the ready to run list has priority.
+ *   2) An idle, ready to run task's priority has been raised above the
+ *      the priority of the current, running task and it now has the
+ *      priority.
+ *
+ * Inputs:
+ *   tcb: The TCB of the task that has been reprioritized
+ *   priority: The new task priority
+ *
+ ****************************************************************************/
+
+void up_reprioritize_rtr(_TCB *tcb, ubyte priority)
+{
+  /* Verify that the caller is sane */
+
+  if (tcb->task_state < FIRST_READY_TO_RUN_STATE ||
+      tcb->task_state > LAST_READY_TO_RUN_STATE ||
+      priority < SCHED_PRIORITY_MIN || 
+      priority > SCHED_PRIORITY_MAX)
+    {
+       PANIC(OSERR_BADREPRIORITIZESTATE);
+    }
+  else
+    {
+      _TCB *rtcb = (_TCB*)g_readytorun.head;
+      boolean switch_needed;
+
+      slldbg("TCB=%p PRI=%d\n", tcb, priority);
+
+      /* Remove the tcb task from the ready-to-run list.
+       * sched_removereadytorun will return TRUE if we just
+       * remove the head of the ready to run list.
+       */
+
+      switch_needed = sched_removereadytorun(tcb);
+
+      /* Setup up the new task priority */
+
+      tcb->sched_priority = (ubyte)priority;
+
+      /* Return the task to the specified blocked task list.
+       * sched_addreadytorun will return TRUE if the task was
+       * added to the new list.  We will need to perform a context
+       * switch only if the EXCLUSIVE or of the two calls is non-zero
+       * (i.e., one and only one the calls changes the head of the
+       * ready-to-run list).
+       */
+
+      switch_needed ^= sched_addreadytorun(tcb);
+
+      /* Now, perform the context switch if one is needed */
+
+      if (switch_needed)
+        {
+          /* If we are going to do a context switch, then now is the right
+           * time to add any pending tasks back into the ready-to-run list.
+           * task list now
+           */
+
+          if (g_pendingtasks.head)
+            {
+              sched_mergepending();
+            }
+
+         /* Are we in an interrupt handler? */
+
+          if (current_regs)
+            {
+              /* Yes, then we have to do things differently.
+               * Just copy the current_regs into the OLD rtcb.
+               */
+
+               up_savestate(rtcb->xcp.regs);
+
+              /* Restore the exception context of the rtcb at the (new) head 
+               * of the g_readytorun task list.
+               */
+
+              rtcb = (_TCB*)g_readytorun.head;
+              slldbg("New Active Task TCB=%p\n", rtcb);
+
+              /* Then switch contexts */
+
+              up_restorestate(rtcb->xcp.regs);
+            }
+
+          /* No, then we will need to perform the user context switch */
+
+          else
+            {
+              /* Switch context to the context of the task at the head of the
+               * ready to run list.
+               */
+
+              _TCB *nexttcb = (_TCB*)g_readytorun.head;
+              up_switchcontext(rtcb->xcp.regs, nexttcb->xcp.regs);
+
+              /* up_switchcontext forces a context switch to the task at the
+               * head of the ready-to-run list.  It does not 'return' in the
+               * normal sense.  When it does return, it is because the blocked
+               * task is again ready to run and has execution priority.
+               */
+            }
+        }
+    }
+}