/**************************************************************************** * sched/paging/pg_miss.c * * Copyright (C) 2010 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #ifdef CONFIG_PAGING #include "sched/sched.h" #include "paging/paging.h" /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: pg_miss * * Description: * This function is called from architecture-specific memory segmentation * 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 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 * 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 struct tcb_s *ftcb = this_task(); FAR struct tcb_s *wtcb; /* Sanity checking * * ASSERT if the currently executing task is the page fill worker thread. * The page fill worker thread is how the page fault is resolved and * all logic associated with the page fill worker must be "locked" and * always present in memory. */ pginfo("Blocking TCB: %p PID: %d\n", ftcb, ftcb->pid); 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 */ pginfo("New worker priority. %d->%d\n", wtcb->sched_priority, ftcb->sched_priority); 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_pftcb) { pginfo("Signaling worker. PID: %d\n", g_pgworker); kill(g_pgworker, SIGWORK); } } #endif /* CONFIG_PAGING */