/**************************************************************************** * sched/work/work_inherit.c * * Copyright (C) 2014, 2016 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 "sched/sched.h" #include "wqueue/wqueue.h" #if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_LPWORK) && \ defined(CONFIG_PRIORITY_INHERITANCE) /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: lpwork_boostworker * * Description: * Called by the work queue client to assure that the priority of the low- * priority worker thread is at least at the requested level, reqprio. This * function would normally be called just before calling work_queue(). * * Parameters: * reqprio - Requested minimum worker thread priority * * Return Value: * None * ****************************************************************************/ static void lpwork_boostworker(pid_t wpid, uint8_t reqprio) { FAR struct tcb_s *wtcb; /* Get the TCB of the low priority worker thread from the process ID. */ wtcb = sched_gettcb(wpid); DEBUGASSERT(wtcb); #if CONFIG_SEM_NNESTPRIO > 0 /* If the priority of the client thread that is greater than the base * priority of the worker thread, then we may need to adjust the worker * thread's priority now or later to that priority. */ if (reqprio > wtcb->base_priority) { /* If the new priority is greater than the current, possibly already * boosted priority of the worker thread, then we will have to raise * the worker thread's priority now. */ if (reqprio > wtcb->sched_priority) { /* If the current priority of worker thread has already been * boosted, then add the boost priority to the list of restoration * priorities. When the higher priority waiter thread gets its * count, then we need to revert the worker thread to this saved * priority (not to its base priority). */ if (wtcb->sched_priority > wtcb->base_priority) { /* Save the current, boosted priority of the worker thread. */ if (wtcb->npend_reprio < CONFIG_SEM_NNESTPRIO) { wtcb->pend_reprios[wtcb->npend_reprio] = wtcb->sched_priority; wtcb->npend_reprio++; } else { serr("ERROR: CONFIG_SEM_NNESTPRIO exceeded\n"); DEBUGASSERT(wtcb->npend_reprio < CONFIG_SEM_NNESTPRIO); } } /* Raise the priority of the worker. This cannot cause a context * switch because we have preemption disabled. The worker thread * may be marked "pending" and the switch may occur during * sched_unblock() processing. */ (void)sched_setpriority(wtcb, reqprio); } else { /* The new priority is above the base priority of the worker, * but not as high as its current working priority. Just put it * in the list of pending restoration priorities so that when the * higher priority thread gets its count, we can revert to this * saved priority and not to the base priority. */ if (wtcb->npend_reprio < CONFIG_SEM_NNESTPRIO) { wtcb->pend_reprios[wtcb->npend_reprio] = reqprio; wtcb->npend_reprio++; } else { serr("ERROR: CONFIG_SEM_NNESTPRIO exceeded\n"); DEBUGASSERT(wtcb->npend_reprio < CONFIG_SEM_NNESTPRIO); } } } #else /* If the priority of the client thread that is less than of equal to the * priority of the worker thread, then do nothing because the thread is * already running at a sufficient priority. */ if (reqprio > wtcb->sched_priority) { /* Raise the priority of the worker thread. This cannot cause * context switch because we have preemption disabled. The task * will be marked "pending" and the switch will occur during * sched_unlock() processing. */ (void)sched_setpriority(wtcb, reqprio); } #endif } /**************************************************************************** * Name: lpwork_restoreworker * * Description: * This function is called to restore the priority after it was previously * boosted. This is often done by client logic on the worker thread when * the scheduled work completes. It will check if we need to drop the * priority of the worker thread. * * Parameters: * reqprio - Previously requested minimum worker thread priority to be * "unboosted" * * Return Value: * None * ****************************************************************************/ static void lpwork_restoreworker(pid_t wpid, uint8_t reqprio) { FAR struct tcb_s *wtcb; #if CONFIG_SEM_NNESTPRIO > 0 uint8_t wpriority; int index; int selected; #endif /* Get the TCB of the low priority worker thread from the process ID. */ wtcb = sched_gettcb(wpid); DEBUGASSERT(wtcb); /* Was the priority of the worker thread boosted? If so, then drop its * priority back to the correct level. What is the correct level? */ if (wtcb->sched_priority != wtcb->base_priority) { #if CONFIG_SEM_NNESTPRIO > 0 /* Are there other, pending priority levels to revert to? */ if (wtcb->npend_reprio < 1) { /* No... the worker thread has only been boosted once. * npend_reprio should be 0 and the boosted priority should be the * priority of the client task (reqprio) * * That latter assumption may not be true if the client's priority * was also boosted so that it no longer matches the wtcb's * sched_priority. Or if CONFIG_SEM_NNESTPRIO is too small (so * that we do not have a proper record of the reprioritizations). */ DEBUGASSERT(/* wtcb->sched_priority == reqprio && */ wtcb->npend_reprio == 0); /* Reset the worker's priority back to the base priority. */ sched_reprioritize(wtcb, wtcb->base_priority); } /* There are multiple pending priority levels. The worker thread's * "boosted" priority could greater than or equal to "reqprio" (it could * be greater if its priority we boosted because it also holds some * semaphore). */ else if (wtcb->sched_priority <= reqprio) { /* The worker thread has been boosted to the same priority as the * waiter thread that just received the count. We will simply * reprioritize to the next highest pending priority. */ /* Find the highest pending priority and remove it from the list */ for (index = 1, selected = 0; index < wtcb->npend_reprio; index++) { if (wtcb->pend_reprios[index] > wtcb->pend_reprios[selected]) { selected = index; } } /* Remove the highest priority pending priority from the list */ wpriority = wtcb->pend_reprios[selected]; index = wtcb->npend_reprio - 1; if (index > 0) { wtcb->pend_reprios[selected] = wtcb->pend_reprios[index]; } wtcb->npend_reprio = index; /* And apply that priority to the thread (while retaining the * base_priority) */ sched_setpriority(wtcb, wpriority); } else { /* The worker thread has been boosted to a higher priority than the * waiter task. The pending priority should be in the list (unless * it was lost because of of list overflow or because the worker * was reprioritized again unbeknownst to the priority inheritance * logic). * * Search the list for the matching priority. */ for (index = 0; index < wtcb->npend_reprio; index++) { /* Does this pending priority match the priority of the thread * that just received the count? */ if (wtcb->pend_reprios[index] == reqprio) { /* Yes, remove it from the list */ selected = wtcb->npend_reprio - 1; if (selected > 0) { wtcb->pend_reprios[index] = wtcb->pend_reprios[selected]; } wtcb->npend_reprio = selected; break; } } } #else /* There is no alternative restore priorities, drop the priority * of the worker thread all the way back to the threads "base" * priority. */ sched_reprioritize(wtcb, wtcb->base_priority); #endif } } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: lpwork_boostpriority * * Description: * Called by the work queue client to assure that the priority of the low- * priority worker thread is at least at the requested level, reqprio. This * function would normally be called just before calling work_queue(). * * Parameters: * reqprio - Requested minimum worker thread priority * * Return Value: * None * ****************************************************************************/ void lpwork_boostpriority(uint8_t reqprio) { irqstate_t flags; int wndx; /* Clip to the configured maximum priority */ if (reqprio > CONFIG_SCHED_LPWORKPRIOMAX) { reqprio = CONFIG_SCHED_LPWORKPRIOMAX; } /* Prevent context switches until we get the priorities right */ flags = enter_critical_section(); sched_lock(); /* Adjust the priority of every worker thread */ for (wndx = 0; wndx < CONFIG_SCHED_LPNTHREADS; wndx++) { lpwork_boostworker(g_lpwork.worker[wndx].pid, reqprio); } sched_unlock(); leave_critical_section(flags); } /**************************************************************************** * Name: lpwork_restorepriority * * Description: * This function is called to restore the priority after it was previously * boosted. This is often done by client logic on the worker thread when * the scheduled work completes. It will check if we need to drop the * priority of the worker thread. * * Parameters: * reqprio - Previously requested minimum worker thread priority to be * "unboosted" * * Return Value: * None * ****************************************************************************/ void lpwork_restorepriority(uint8_t reqprio) { irqstate_t flags; int wndx; /* Clip to the configured maximum priority */ if (reqprio > CONFIG_SCHED_LPWORKPRIOMAX) { reqprio = CONFIG_SCHED_LPWORKPRIOMAX; } /* Prevent context switches until we get the priorities right */ flags = enter_critical_section(); sched_lock(); /* Adjust the priority of every worker thread */ for (wndx = 0; wndx < CONFIG_SCHED_LPNTHREADS; wndx++) { lpwork_restoreworker(g_lpwork.worker[wndx].pid, reqprio); } sched_unlock(); leave_critical_section(flags); } #endif /* CONFIG_SCHED_WORKQUEUE && CONFIG_SCHED_LPWORK && \ * CONFIG_PRIORITY_INHERITANCE */