187 lines
7.1 KiB
C
187 lines
7.1 KiB
C
/****************************************************************************
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* sched/paging/pg_miss.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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 <assert.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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#include <nuttx/signal.h>
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#ifdef CONFIG_PAGING
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#include "sched/sched.h"
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#include "paging/paging.h"
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/****************************************************************************
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* Public 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_switch_context() to block the task at the head of the
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* ready-to-run list. This should cause an interrupt level context
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* switch 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 = this_task();
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FAR struct tcb_s *wtcb;
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bool switch_needed;
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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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pginfo("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_switch_context() to block the task at the head of the
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* ready-to-run list. This should cause an interrupt level context
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* switch 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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* Need to firstly check that this is not the idle task,descheduling
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* that isn't going to end well.
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*/
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DEBUGASSERT(!is_idle_task(ftcb));
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/* Remove the tcb task from the ready-to-run list. */
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switch_needed = nxsched_remove_readytorun(ftcb, true);
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/* Add the task to the specified blocked task list */
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ftcb->task_state = TSTATE_WAIT_PAGEFILL;
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nxsched_add_prioritized(ftcb, &g_waitingforfill);
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/* Now, perform the context switch if one is needed */
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if (switch_needed)
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{
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up_switch_context(this_task(), ftcb);
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}
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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 = nxsched_get_tcb(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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pginfo("New worker priority. %d->%d\n",
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wtcb->sched_priority, ftcb->sched_priority);
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nxsched_set_priority(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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pginfo("Signaling worker. PID: %d\n", g_pgworker);
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nxsig_kill(g_pgworker, SIGWORK);
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}
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}
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#endif /* CONFIG_PAGING */
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