180 lines
7.3 KiB
C
180 lines
7.3 KiB
C
/****************************************************************************
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* sched/pg_miss.c
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*
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* Copyright (C) 2010 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/arch.h>
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#include <nuttx/sched.h>
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#include <nuttx/page.h>
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#ifdef CONFIG_PAGING
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#include "os_internal.h"
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#include "pg_internal.h"
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/****************************************************************************
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* Global Functions
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****************************************************************************/
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/****************************************************************************
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* Name: pg_miss
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*
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* Description:
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* This function is called from architecture-specific memory segmentation
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* fault handling logic. This function will perform the following
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* operations:
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*
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* 1) Sanity checking.
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* - ASSERT if the currently executing task is the page fill worker
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* thread. The page fill worker thread is how the page fault
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* is resolved and all logic associated with the page fill worker
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* must be "locked" and always present in memory.
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* - ASSERT if an interrupt was executing at the time of the exception.
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* 2) Block the currently executing task.
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* - Call up_block_task() to block the task at the head of the ready-
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* to-run list. This should cause an interrupt level context switch
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* to the next highest priority task.
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* - The blocked task will be marked with state TSTATE_WAIT_PAGEFILL
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* and will be retained in the g_waitingforfill prioritized task
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* list.
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* 3) Boost the page fill worker thread priority.
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* - Check the priority of the task at the head of the g_waitingforfill
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* list. If the priority of that task is higher than the current
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* priority of the page fill worker thread, then boost the priority
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* of the page fill worker thread to that priority.
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* 4) Signal the page fill worker thread.
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* - Is there a page fill pending? If not then signal the worker
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* thread to start working on the queued page fill requests.
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*
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* Input Parameters:
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* None - The head of the ready-to-run list is assumed to be task that
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* caused the exception.
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*
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* Returned Value:
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* None - Either this function function succeeds or an assertion occurs.
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*
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* Assumptions:
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* - It is assumed that this function is called from the level of an
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* exception handler and that all interrupts are disabled.
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* - It is assumed that currently executing task (the one at the head of
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* the ready-to-run list) is the one that cause the fault. This will
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* always be true unless the page fault occurred in an interrupt handler.
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* Interrupt handling logic must always be present and "locked" into
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* memory.
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* - As mentioned above, the task causing the page fault must not be the
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* page fill worker thread because that is the only way to complete the
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* page fill.
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*
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* NOTES:
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* 1. One way to accomplish this would be a two pass link phase:
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* - In the first phase, create a partially linked objected containing
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* all interrupt/exception handling logic, the page fill worker thread
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* plus all parts of the IDLE thread (which must always be available
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* for execution).
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* - All of the .text and .rodata sections of this partial link should
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* be collected into a single section.
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* - The second link would link the partially linked object along with
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* the remaining object to produce the final binary. The linker
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* script should position the "special" section so that it lies
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* in a reserved, "non-swappable" region.
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*
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****************************************************************************/
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void pg_miss(void)
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{
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FAR struct tcb_s *ftcb = (FAR struct tcb_s*)g_readytorun.head;
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FAR struct tcb_s *wtcb;
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/* Sanity checking
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*
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* ASSERT if the currently executing task is the page fill worker thread.
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* The page fill worker thread is how the page fault is resolved and
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* all logic associated with the page fill worker must be "locked" and
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* always present in memory.
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*/
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pglldbg("Blocking TCB: %p PID: %d\n", ftcb, ftcb->pid);
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DEBUGASSERT(g_pgworker != ftcb->pid);
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/* Block the currently executing task
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* - Call up_block_task() to block the task at the head of the ready-
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* to-run list. This should cause an interrupt level context switch
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* to the next highest priority task.
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* - The blocked task will be marked with state TSTATE_WAIT_PAGEFILL
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* and will be retained in the g_waitingforfill prioritized task list.
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*/
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up_block_task(ftcb, TSTATE_WAIT_PAGEFILL);
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/* Boost the page fill worker thread priority.
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* - Check the priority of the task at the head of the g_waitingforfill
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* list. If the priority of that task is higher than the current
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* priority of the page fill worker thread, then boost the priority
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* of the page fill worker thread to that priority.
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*/
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wtcb = sched_gettcb(g_pgworker);
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DEBUGASSERT(wtcb != NULL);
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if (wtcb->sched_priority < ftcb->sched_priority)
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{
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/* Reprioritize the page fill worker thread */
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pgllvdbg("New worker priority. %d->%d\n",
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wtcb->sched_priority, ftcb->sched_priority);
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sched_setpriority(wtcb, ftcb->sched_priority);
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}
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/* Signal the page fill worker thread.
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* - Is there a page fill pending? If not then signal the worker
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* thread to start working on the queued page fill requests.
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*/
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if (!g_pftcb)
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{
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pglldbg("Signaling worker. PID: %d\n", g_pgworker);
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kill(g_pgworker, SIGWORK);
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}
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}
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#endif /* CONFIG_PAGING */
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