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Diffstat (limited to 'nuttx/sched/pg_miss.c')
-rw-r--r-- | nuttx/sched/pg_miss.c | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/nuttx/sched/pg_miss.c b/nuttx/sched/pg_miss.c new file mode 100644 index 000000000..7abf0e2c2 --- /dev/null +++ b/nuttx/sched/pg_miss.c @@ -0,0 +1,179 @@ +/**************************************************************************** + * 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 <errno.h> +#include <debug.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 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 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 _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. + */ + + pglldbg("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 */ + + pgllvdbg("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) + { + pglldbg("Signaling worker. PID: %d\n", g_pgworker); + kill(g_pgworker, SIGWORK); + } +} + +#endif /* CONFIG_PAGING */ |