Beginning to add on-demand paging logic

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2850 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 175 insertions, 0 deletions

diff --git a/nuttx/sched/pg_miss.c b/nuttx/sched/pg_miss.c
new file mode 100644
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+/****************************************************************************
+ * sched/pg_miss.c
+ *
+ *   Copyright (C) 2010 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 <debug.h>
+#include <errno.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/sched.h>
+#include <nuttx/page.h>
+
+#ifdef CONFIG_PAGING
+
+#include "os_internal.h"
+#include "pg_internal.h"
+
+/****************************************************************************
+ * Global Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: pg_miss
+ *
+ * Description:
+ *   This function is called from architecture-specific memory segmentaion
+ *   fault handling logic.  This function will perform the following
+ *   operations:
+ *
+ *   1) Sanity checking.
+ *      - ASSERT if the currently executing task is the page fill worker
+ *        thread.  The page fill worker thread is how the the page fault
+ *        is resolved and all logic associated with the page fill worker
+ *        must be "locked" and always present in memory.
+ *      - ASSERT if an interrupt was executing at the time of the exception.
+ *   2) Block the currently executing task.
+ *      - Call up_block_task() to block the task at the head of the ready-
+ *        to-run list.  This should cause an interrupt level context switch
+ *        to the next highest priority task.
+ *      - The blocked task will be marked with state TSTATE_WAIT_PAGEFILL
+ *        and will be retained in the g_waitingforfill prioritized task
+ *        list.
+ *   3) Boost the page fill worker thread priority.
+ *      - Check the priority of the task at the head of the g_waitingforfill
+ *        list.  If the priority of that task is higher than the current
+ *        priority of the page fill worker thread, then boost the priority
+ *        of the page fill worker thread to that priority.
+ *   4) Signal the page fill worker thread.
+ *      - Is there a page fill pending?  If not then signal the worker
+ *        thread to start working on the queued page fill requests.
+ *
+ * Input Parameters:
+ *   None - The head of the ready-to-run list is assumed to be task that
+ *   caused the exception.
+ *
+ * Returned Value:
+ *   None - Either this function function succeeds or an assertion occurs.
+ *
+ * Assumptions:
+ *   - It is assumed that this function is called from the level of an
+ *     exception handler and that all interrupts are disabled.
+ *   - It is assumed that currently executing task (the one at the head of
+ *     the ready-to-run list) is the one that cause the fault.  This will
+ *     always be true unless the page fault occurred in an interrupt handler.
+ *     Interrupt handling logic must always be present and "locked" into
+ *     memory.
+ *   - As mentioned above, the task causing the page fault must not be the
+ *     the page fill worker thread because that is the only way to complete
+ *     the page fill.
+ *
+ * NOTES:
+ *   1. One way to accomplish this would be a two pass link phase:
+ *      - In the first phase, create a partially linked objected containing
+ *        all interrupt/exception handling logic, the page fill worker thread
+ *        plus all parts of the IDLE thread (which must always be available
+ *        for execution).
+ *      - All of the .text and .rodata sections of this partial link should
+ *        be collected into a single section.
+ *      - The second link would link the partially linked object along with
+ *        the remaining object to produce the final binary.  The linker
+ *        script should position the "special" section so that it lies
+ *        in a reserved, "non-swappable" region.
+ *
+ ****************************************************************************/
+
+void pg_miss(void)
+{
+  FAR _TCB *ftcb = (FAR _TCB*)g_readytorun.head;
+  FAR _TCB *wtcb;
+
+  /* Sanity checking
+   *
+   * ASSERT if the currently executing task is the page fill worker thread.
+   * The page fill worker thread is how the the page fault is resolved and
+   * all logic associated with the page fill worker must be "locked" and
+   * always present in memory.
+   */
+
+  DEBUGASSERT(g_pgworker != ftcb->pid);
+
+  /* Block the currently executing task
+   * - Call up_block_task() to block the task at the head of the ready-
+   *   to-run list.  This should cause an interrupt level context switch
+   *   to the next highest priority task.
+   * - The blocked task will be marked with state TSTATE_WAIT_PAGEFILL
+   *   and will be retained in the g_waitingforfill prioritized task list.
+   */
+
+  up_block_task(ftcb, TSTATE_WAIT_PAGEFILL);
+
+  /* Boost the page fill worker thread priority.
+   * - Check the priority of the task at the head of the g_waitingforfill
+   *   list.  If the priority of that task is higher than the current
+   *   priority of the page fill worker thread, then boost the priority
+   *   of the page fill worker thread to that priority.
+   */
+
+  wtcb = sched_gettcb(g_pgworker);
+  DEBUGASSERT(wtcb != NULL);
+
+  if (wtcb->sched_priority < ftcb->sched_priority)
+    {
+      /* Reprioritize the page fill worker thread */
+
+      sched_setpriority(wtcb, ftcb->sched_priority);
+    }
+
+  /* Signal the page fill worker thread.
+   * - Is there a page fill pending?  If not then signal the worker
+   *   thread to start working on the queued page fill requests.
+   */
+
+  if (!g_filltcb)
+    {
+      kill(g_pgworker, SIGWORK);
+    }
+}
+
+#endif /* CONFIG_PAGING */