/**************************************************************************** * sched/semaphore/sem_holder.c * * Copyright (C) 2009-2011, 2013, 2016-2019 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 "sched/sched.h" #include "semaphore/semaphore.h" #ifdef CONFIG_PRIORITY_INHERITANCE /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /* Configuration ************************************************************/ #ifndef CONFIG_SEM_PREALLOCHOLDERS # define CONFIG_SEM_PREALLOCHOLDERS 0 #endif /**************************************************************************** * Private Type Declarations ****************************************************************************/ typedef int (*holderhandler_t)(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg); /**************************************************************************** * Private Data ****************************************************************************/ /* Preallocated holder structures */ #if CONFIG_SEM_PREALLOCHOLDERS > 0 static struct semholder_s g_holderalloc[CONFIG_SEM_PREALLOCHOLDERS]; static FAR struct semholder_s *g_freeholders; #endif /**************************************************************************** * Name: nxsem_allocholder ****************************************************************************/ static inline FAR struct semholder_s *nxsem_allocholder(sem_t *sem) { FAR struct semholder_s *pholder; /* Check if the "built-in" holder is being used. We have this built-in * holder to optimize for the simplest case where semaphores are only * used to implement mutexes. */ #if CONFIG_SEM_PREALLOCHOLDERS > 0 pholder = g_freeholders; if (pholder != NULL) { /* Remove the holder from the free list an put it into the semaphore's * holder list */ g_freeholders = pholder->flink; pholder->flink = sem->hhead; sem->hhead = pholder; /* Make sure the initial count is zero */ pholder->counts = 0; } #else if (sem->holder[0].htcb == NULL) { pholder = &sem->holder[0]; pholder->counts = 0; } else if (sem->holder[1].htcb == NULL) { pholder = &sem->holder[1]; pholder->counts = 0; } #endif else { serr("ERROR: Insufficient pre-allocated holders\n"); pholder = NULL; } DEBUGASSERT(pholder != NULL); return pholder; } /**************************************************************************** * Name: nxsem_findholder ****************************************************************************/ static FAR struct semholder_s *nxsem_findholder(sem_t *sem, FAR struct tcb_s *htcb) { FAR struct semholder_s *pholder; #if CONFIG_SEM_PREALLOCHOLDERS > 0 /* Try to find the holder in the list of holders associated with this * semaphore */ for (pholder = sem->hhead; pholder != NULL; pholder = pholder->flink) { if (pholder->htcb == htcb) { /* Got it! */ return pholder; } } #else int i; pholder = NULL; /* We have two hard-allocated holder structures in sem_t */ for (i = 0; i < 2; i++) { pholder = &sem->holder[i]; if (pholder->htcb == htcb) { /* Got it! */ return pholder; } } #endif /* The holder does not appear in the list */ return NULL; } /**************************************************************************** * Name: nxsem_findorallocateholder ****************************************************************************/ static inline FAR struct semholder_s * nxsem_findorallocateholder(sem_t *sem, FAR struct tcb_s *htcb) { FAR struct semholder_s *pholder = nxsem_findholder(sem, htcb); if (!pholder) { pholder = nxsem_allocholder(sem); } return pholder; } /**************************************************************************** * Name: nxsem_freeholder ****************************************************************************/ static inline void nxsem_freeholder(sem_t *sem, FAR struct semholder_s *pholder) { #if CONFIG_SEM_PREALLOCHOLDERS > 0 FAR struct semholder_s *curr; FAR struct semholder_s *prev; #endif /* Release the holder and counts */ pholder->htcb = NULL; pholder->counts = 0; #if CONFIG_SEM_PREALLOCHOLDERS > 0 /* Search the list for the matching holder */ for (prev = NULL, curr = sem->hhead; curr && curr != pholder; prev = curr, curr = curr->flink); if (curr != NULL) { /* Remove the holder from the list */ if (prev != NULL) { prev->flink = pholder->flink; } else { sem->hhead = pholder->flink; } /* And put it in the free list */ pholder->flink = g_freeholders; g_freeholders = pholder; } #endif } /**************************************************************************** * Name: nxsem_findandfreeholder ****************************************************************************/ static inline void nxsem_findandfreeholder(sem_t *sem, FAR struct tcb_s *htcb) { FAR struct semholder_s *pholder = nxsem_findholder(sem, htcb); /* When no more counts are held, remove the holder from the list. The * count was decremented in nxsem_releaseholder. */ if (pholder != NULL && pholder->counts <= 0) { nxsem_freeholder(sem, pholder); } } /**************************************************************************** * Name: nxsem_foreachholder ****************************************************************************/ static int nxsem_foreachholder(FAR sem_t *sem, holderhandler_t handler, FAR void *arg) { FAR struct semholder_s *pholder; int ret = 0; #if CONFIG_SEM_PREALLOCHOLDERS > 0 FAR struct semholder_s *next; for (pholder = sem->hhead; pholder && ret == 0; pholder = next) { /* In case this holder gets deleted */ next = pholder->flink; /* Check if there is a handler... there should always be one * in this configuration. */ if (pholder->htcb != NULL) { /* Call the handler */ ret = handler(pholder, sem, arg); } } #else int i; /* We have two hard-allocated holder structures in sem_t */ for (i = 0; i < 2; i++) { pholder = &sem->holder[i]; /* The hard-allocated containers may hold a NULL holder */ if (pholder->htcb != NULL) { /* Call the handler */ ret = handler(pholder, sem, arg); } } #endif return ret; } /**************************************************************************** * Name: nxsem_recoverholders ****************************************************************************/ #if CONFIG_SEM_PREALLOCHOLDERS > 0 static int nxsem_recoverholders(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg) { nxsem_freeholder(sem, pholder); return 0; } #endif /**************************************************************************** * Name: nxsem_boostholderprio ****************************************************************************/ static int nxsem_boostholderprio(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg) { FAR struct tcb_s *htcb = (FAR struct tcb_s *)pholder->htcb; FAR struct tcb_s *rtcb = (FAR struct tcb_s *)arg; /* Make sure that the holder thread is still active. If it exited without * releasing its counts, then that would be a bad thing. But we can take * no real action because we don't know know that the program is doing. * Perhaps its plan is to kill a thread, then destroy the semaphore. */ if (!sched_verifytcb(htcb)) { #if 0 /* DSA: sometimes crashes when Telnet calls external cmd (i.e. 'i2c') */ serr("ERROR: TCB 0x%08x is a stale handle, counts lost\n", htcb); DEBUGPANIC(); #endif nxsem_freeholder(sem, pholder); } #if CONFIG_SEM_NNESTPRIO > 0 /* If the priority of the thread that is waiting for a count is greater * than the base priority of the thread holding a count, then we may need * to adjust the holder's priority now or later to that priority. */ else if (rtcb->sched_priority > htcb->base_priority) { /* If the new priority is greater than the current, possibly already * boosted priority of the holder thread, then we will have to raise * the holder's priority now. */ if (rtcb->sched_priority > htcb->sched_priority) { /* If the current priority of holder 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 holder thread to this saved * priority (not to its base priority). */ if (htcb->sched_priority > htcb->base_priority) { /* Save the current, boosted priority of the holder thread. */ if (htcb->npend_reprio < CONFIG_SEM_NNESTPRIO) { htcb->pend_reprios[htcb->npend_reprio] = htcb->sched_priority; htcb->npend_reprio++; } else { serr("ERROR: CONFIG_SEM_NNESTPRIO exceeded\n"); DEBUGASSERT(htcb->npend_reprio < CONFIG_SEM_NNESTPRIO); } } /* Raise the priority of the thread holding of the semaphore. * This cannot cause a context switch because we have preemption * disabled. The holder thread may be marked "pending" and the * switch may occur during up_block_task() processing. */ nxsched_setpriority(htcb, rtcb->sched_priority); } else { /* The new priority is above the base priority of the holder, * 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 (htcb->npend_reprio < CONFIG_SEM_NNESTPRIO) { htcb->pend_reprios[htcb->npend_reprio] = rtcb->sched_priority; htcb->npend_reprio++; } else { serr("ERROR: CONFIG_SEM_NNESTPRIO exceeded\n"); DEBUGASSERT(htcb->npend_reprio < CONFIG_SEM_NNESTPRIO); } } } #else /* If the priority of the thread that is waiting for a count is less than * of equal to the priority of the thread holding a count, then do nothing * because the thread is already running at a sufficient priority. */ else if (rtcb->sched_priority > htcb->sched_priority) { /* Raise the priority of the holder of the semaphore. This * cannot cause a context switch because we have preemption * disabled. The task will be marked "pending" and the switch * will occur during up_block_task() processing. */ nxsched_setpriority(htcb, rtcb->sched_priority); } #endif return 0; } /**************************************************************************** * Name: nxsem_verifyholder ****************************************************************************/ #ifdef CONFIG_DEBUG_ASSERTIONS static int nxsem_verifyholder(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg) { #if 0 /* Need to revisit this, but these assumptions seem to be untrue -- \ * OR there is a bug??? */ FAR struct tcb_s *htcb = (FAR struct tcb_s *)pholder->htcb; /* Called after a semaphore has been released (incremented), the semaphore * could is non-negative, and there is no thread waiting for the count. * In this case, the priority of the holder should not be boosted. */ #if CONFIG_SEM_NNESTPRIO > 0 DEBUGASSERT(htcb->npend_reprio == 0); #endif DEBUGASSERT(htcb->sched_priority == htcb->base_priority); #endif return 0; } #endif /**************************************************************************** * Name: nxsem_dumpholder ****************************************************************************/ #if defined(CONFIG_DEBUG_INFO) && defined(CONFIG_SEM_PHDEBUG) static int nxsem_dumpholder(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg) { #if CONFIG_SEM_PREALLOCHOLDERS > 0 _info(" %08x: %08x %08x %04x\n", pholder, pholder->flink, pholder->htcb, pholder->counts); #else _info(" %08x: %08x %04x\n", pholder, pholder->htcb, pholder->counts); #endif return 0; } #endif /**************************************************************************** * Name: nxsem_restoreholderprio ****************************************************************************/ static int nxsem_restoreholderprio(FAR struct tcb_s *htcb, FAR sem_t *sem, FAR void *arg) { FAR struct semholder_s *pholder = 0; #if CONFIG_SEM_NNESTPRIO > 0 FAR struct tcb_s *stcb = (FAR struct tcb_s *)arg; int rpriority; int i; int j; #endif /* Make sure that the holder thread is still active. If it exited without * releasing its counts, then that would be a bad thing. But we can take * no real action because we don't know know that the program is doing. * Perhaps its plan is to kill a thread, then destroy the semaphore. */ if (!sched_verifytcb(htcb)) { serr("ERROR: TCB 0x%08x is a stale handle, counts lost\n", htcb); DEBUGPANIC(); pholder = nxsem_findholder(sem, htcb); if (pholder != NULL) { nxsem_freeholder(sem, pholder); } } /* Was the priority of the holder thread boosted? If so, then drop its * priority back to the correct level. What is the correct level? */ else if (htcb->sched_priority != htcb->base_priority) { #if CONFIG_SEM_NNESTPRIO > 0 /* Are there other, pending priority levels to revert to? */ if (htcb->npend_reprio < 1) { /* No... the holder thread has only been boosted once. * npend_reprio should be 0 and the boosted priority should be the * priority of the task that just got the semaphore * (stcb->sched_priority) * * That latter assumption may not be true if the stcb's priority * was also boosted so that it no longer matches the htcb's * sched_priority. Or if CONFIG_SEM_NNESTPRIO is too small (so * that we do not have a proper record of the reprioritizations). */ DEBUGASSERT(/* htcb->sched_priority == stcb->sched_priority && */ htcb->npend_reprio == 0); /* Reset the holder's priority back to the base priority. */ nxsched_reprioritize(htcb, htcb->base_priority); } /* There are multiple pending priority levels. The holder thread's * "boosted" priority could greater than or equal to * "stcb->sched_priority" (it could be greater if its priority we * boosted because it also holds another semaphore). */ else if (htcb->sched_priority <= stcb->sched_priority) { /* The holder 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 priority that we have in * rpriority. */ /* Find the highest pending priority and remove it from the list */ for (i = 1, j = 0; i < htcb->npend_reprio; i++) { if (htcb->pend_reprios[i] > htcb->pend_reprios[j]) { j = i; } } /* Remove the highest priority pending priority from the list */ rpriority = htcb->pend_reprios[j]; i = htcb->npend_reprio - 1; if (i > 0) { htcb->pend_reprios[j] = htcb->pend_reprios[i]; } htcb->npend_reprio = i; /* And apply that priority to the thread (while retaining the * base_priority) */ nxsched_setpriority(htcb, rpriority); } else { /* The holder 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 holder * was reprioritized again unbeknownst to the priority inheritance * logic). * * Search the list for the matching priority. */ for (i = 0; i < htcb->npend_reprio; i++) { /* Does this pending priority match the priority of the thread * that just received the count? */ if (htcb->pend_reprios[i] == stcb->sched_priority) { /* Yes, remove it from the list */ j = htcb->npend_reprio - 1; if (j > 0) { htcb->pend_reprios[i] = htcb->pend_reprios[j]; } htcb->npend_reprio = j; break; } } } #else /* There is no alternative restore priorities, drop the priority * of the holder thread all the way back to the threads "base" * priority. */ nxsched_reprioritize(htcb, htcb->base_priority); #endif } return 0; } /**************************************************************************** * Name: nxsem_restoreholderprioall * * Description: * Reprioritize all holders * ****************************************************************************/ static int nxsem_restoreholderprioall(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg) { return nxsem_restoreholderprio(pholder->htcb, sem, arg); } /**************************************************************************** * Name: nxsem_restoreholderprioA * * Description: * Reprioritize all holders except the currently executing task * ****************************************************************************/ static int nxsem_restoreholderprioA(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg) { FAR struct tcb_s *rtcb = this_task(); if (pholder->htcb != rtcb) { return nxsem_restoreholderprio(pholder->htcb, sem, arg); } return 0; } /**************************************************************************** * Name: nxsem_restoreholderprioB * * Description: * Reprioritize only the currently executing task * ****************************************************************************/ static int nxsem_restoreholderprioB(FAR struct semholder_s *pholder, FAR sem_t *sem, FAR void *arg) { FAR struct tcb_s *rtcb = this_task(); if (pholder->htcb == rtcb) { /* The running task has given up a count on the semaphore */ #if CONFIG_SEM_PREALLOCHOLDERS == 0 /* In the case where there are only 2 holders. This step * is necessary to insure we have space. Release the holder * if all counts have been given up. before reprioritizing * causes a context switch. */ nxsem_findandfreeholder(sem, rtcb); #endif nxsem_restoreholderprio(rtcb, sem, arg); return 1; } return 0; } /**************************************************************************** * Name: nxsem_restorebaseprio_irq * * Description: * This function is called after the an interrupt handler posts a count on * the semaphore. It will check if we need to drop the priority of any * threads holding a count on the semaphore. Their priority could have * been boosted while they held the count. * * Input Parameters: * stcb - The TCB of the task that was just started (if any). If the * post action caused a count to be given to another thread, then stcb * is the TCB that received the count. Note, just because stcb received * the count, it does not mean that it it is higher priority than other * threads. * sem - A reference to the semaphore being posted. * - If the semaphore count is <0 then there are still threads waiting * for a count. stcb should be non-null and will be higher priority * than all of the other threads still waiting. * - If it is ==0 then stcb refers to the thread that got the last count; * no other threads are waiting. * - If it is >0 then there should be no threads waiting for counts and * stcb should be null. * * Returned Value: * None * * Assumptions: * The scheduler is locked. * ****************************************************************************/ static inline void nxsem_restorebaseprio_irq(FAR struct tcb_s *stcb, FAR sem_t *sem) { /* Perform the following actions only if a new thread was given a count. * The thread that received the count should be the highest priority * of all threads waiting for a count from the semaphore. So in that * case, the priority of all holder threads should be dropped to the * next highest pending priority. */ if (stcb != NULL) { /* Drop the priority of all holder threads */ nxsem_foreachholder(sem, nxsem_restoreholderprioall, stcb); } /* If there are no tasks waiting for available counts, then all holders * should be at their base priority. */ #ifdef CONFIG_DEBUG_ASSERTIONS else { nxsem_foreachholder(sem, nxsem_verifyholder, NULL); } #endif } /**************************************************************************** * Name: nxsem_restorebaseprio_task * * Description: * This function is called after the current running task releases a * count on the semaphore. It will check if we need to drop the priority * of any threads holding a count on the semaphore. Their priority could * have been boosted while they held the count. * * Input Parameters: * stcb - The TCB of the task that was just started (if any). If the * post action caused a count to be given to another thread, then stcb * is the TCB that received the count. Note, just because stcb received * the count, it does not mean that it it is higher priority than other * threads. * sem - A reference to the semaphore being posted. * - If the semaphore count is <0 then there are still threads waiting * for a count. stcb should be non-null and will be higher priority * than all of the other threads still waiting. * - If it is ==0 then stcb refers to the thread that got the last count; * no other threads are waiting. * - If it is >0 then there should be no threads waiting for counts and * stcb should be null. * * Returned Value: * None * * Assumptions: * The scheduler is locked. * ****************************************************************************/ static inline void nxsem_restorebaseprio_task(FAR struct tcb_s *stcb, FAR sem_t *sem) { FAR struct tcb_s *rtcb = this_task(); /* Perform the following actions only if a new thread was given a count. * The thread that received the count should be the highest priority * of all threads waiting for a count from the semaphore. So in that * case, the priority of all holder threads should be dropped to the * next highest pending priority. */ if (stcb != NULL) { /* The currently executed thread should be the lower priority * thread that just posted the count and caused this action. * However, we cannot drop the priority of the currently running * thread -- because that will cause it to be suspended. * * So, do this in two passes. First, reprioritizing all holders * except for the running thread. */ nxsem_foreachholder(sem, nxsem_restoreholderprioA, stcb); /* Now, find an reprioritize only the ready to run task */ nxsem_foreachholder(sem, nxsem_restoreholderprioB, stcb); } /* If there are no tasks waiting for available counts, then all holders * should be at their base priority. */ #ifdef CONFIG_DEBUG_ASSERTIONS else { nxsem_foreachholder(sem, nxsem_verifyholder, NULL); } #endif /* In any case, the currently executing task should have an entry in the * list. Its counts were previously decremented; if it now holds no * counts, then we need to remove it from the list of holders. */ nxsem_findandfreeholder(sem, rtcb); } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: nxsem_initholders * * Description: * Called from nxsem_initialize() to set up semaphore holder information. * * Input Parameters: * None * * Returned Value: * None * * Assumptions: * ****************************************************************************/ void nxsem_initholders(void) { #if CONFIG_SEM_PREALLOCHOLDERS > 0 int i; /* Put all of the pre-allocated holder structures into the free list */ g_freeholders = g_holderalloc; for (i = 0; i < (CONFIG_SEM_PREALLOCHOLDERS - 1); i++) { g_holderalloc[i].flink = &g_holderalloc[i + 1]; } g_holderalloc[CONFIG_SEM_PREALLOCHOLDERS - 1].flink = NULL; #endif } /**************************************************************************** * Name: nxsem_destroyholder * * Description: * Called from nxsem_destroy() to handle any holders of a semaphore * when it is destroyed. * * Input Parameters: * sem - A reference to the semaphore being destroyed * * Returned Value: * None * * Assumptions: * ****************************************************************************/ void nxsem_destroyholder(FAR sem_t *sem) { /* It might be an error if a semaphore is destroyed while there are any * holders of the semaphore (except perhaps the thread that release the * semaphore itself). We actually have to assume that the caller knows * what it is doing because could have killed another thread that is the * actual holder of the semaphore. * * It is also a standard practice to destroy the semaphore while the * caller holds it. Of course, the caller MUST assure that there are no * other holders of the semaphore in this case. This occurs, for example, * when a driver is unlink'ed and the driver instance must be destroyed. * * Therefore, we cannot make any assumptions about the state of the * semaphore or the state of any of the holder threads. So just recover * any stranded holders and hope the task knows what it is doing. */ #if CONFIG_SEM_PREALLOCHOLDERS > 0 if (sem->hhead != NULL) { /* There may be an issue if there are multiple holders of * the semaphore. */ DEBUGASSERT(sem->hhead->flink == NULL); nxsem_foreachholder(sem, nxsem_recoverholders, NULL); } #else /* There may be an issue if there are multiple holders of the semaphore. */ DEBUGASSERT(sem->holder[0].htcb == NULL || sem->holder[1].htcb == NULL); sem->holder[0].htcb = NULL; sem->holder[1].htcb = NULL; #endif } /**************************************************************************** * Name: nxsem_addholder_tcb * * Description: * Called from nxsem_wait() when the calling thread obtains the semaphore; * Called from sem_post() when the waiting thread obtains the semaphore. * * Input Parameters: * htcb - TCB of the thread that just obtained the semaphore * sem - A reference to the incremented semaphore * * Returned Value: * 0 (OK) or -1 (ERROR) if unsuccessful * * Assumptions: * Interrupts are disabled. * ****************************************************************************/ void nxsem_addholder_tcb(FAR struct tcb_s *htcb, FAR sem_t *sem) { FAR struct semholder_s *pholder; /* If priority inheritance is disabled for this thread, then do not add * the holder. If there are never holders of the semaphore, the priority * inheritance is effectively disabled. */ if ((sem->flags & PRIOINHERIT_FLAGS_DISABLE) == 0) { /* Find or allocate a container for this new holder */ pholder = nxsem_findorallocateholder(sem, htcb); if (pholder != NULL) { /* Then set the holder and increment the number of counts held by this * holder */ pholder->htcb = htcb; pholder->counts++; } } } /**************************************************************************** * Name: nxsem_addholder * * Description: * Called from nxsem_wait() when the calling thread obtains the semaphore * * Input Parameters: * sem - A reference to the incremented semaphore * * Returned Value: * 0 (OK) or -1 (ERROR) if unsuccessful * * Assumptions: * Interrupts are disabled. * ****************************************************************************/ void nxsem_addholder(FAR sem_t *sem) { nxsem_addholder_tcb(this_task(), sem); } /**************************************************************************** * Name: void nxsem_boostpriority(sem_t *sem) * * Description: * * * Input Parameters: * None * * Returned Value: * 0 (OK) or -1 (ERROR) if unsuccessful * * Assumptions: * ****************************************************************************/ void nxsem_boostpriority(FAR sem_t *sem) { FAR struct tcb_s *rtcb = this_task(); /* Boost the priority of every thread holding counts on this semaphore * that are lower in priority than the new thread that is waiting for a * count. */ nxsem_foreachholder(sem, nxsem_boostholderprio, rtcb); } /**************************************************************************** * Name: nxsem_releaseholder * * Description: * Called from sem_post() after a thread releases one count on the * semaphore. * * Input Parameters: * sem - A reference to the semaphore being posted * * Returned Value: * None * * Assumptions: * ****************************************************************************/ void nxsem_releaseholder(FAR sem_t *sem) { FAR struct tcb_s *rtcb = this_task(); FAR struct semholder_s *pholder; /* Find the container for this holder */ pholder = nxsem_findholder(sem, rtcb); if (pholder != NULL && pholder->counts > 0) { /* Decrement the counts on this holder -- the holder will be freed * later in nxsem_restorebaseprio. */ pholder->counts--; } } /**************************************************************************** * Name: nxsem_restorebaseprio * * Description: * This function is called after the current running task releases a * count on the semaphore or an interrupt handler posts a new count. It * will check if we need to drop the priority of any threads holding a * count on the semaphore. Their priority could have been boosted while * they held the count. * * Input Parameters: * stcb - The TCB of the task that was just started (if any). If the * post action caused a count to be given to another thread, then stcb * is the TCB that received the count. Note, just because stcb received * the count, it does not mean that it it is higher priority than other * threads. * sem - A reference to the semaphore being posted. * - If the semaphore count is <0 then there are still threads waiting * for a count. stcb should be non-null and will be higher priority * than all of the other threads still waiting. * - If it is ==0 then stcb refers to the thread that got the last count; * no other threads are waiting. * - If it is >0 then there should be no threads waiting for counts and * stcb should be null. * * Returned Value: * None * * Assumptions: * The scheduler is locked. * ****************************************************************************/ void nxsem_restorebaseprio(FAR struct tcb_s *stcb, FAR sem_t *sem) { #if 0 /* DSA: sometimes crashes when Telnet calls external cmd (i.e. 'i2c') */ /* Check our assumptions */ DEBUGASSERT((sem->semcount > 0 && stcb == NULL) || (sem->semcount <= 0 && stcb != NULL)); #endif /* Handler semaphore counts posed from an interrupt handler differently * from interrupts posted from threads. The primary difference is that * if the semaphore is posted from a thread, then the poster thread is * a player in the priority inheritance scheme. The interrupt handler * externally injects the new count without otherwise participating * itself. */ if (up_interrupt_context()) { nxsem_restorebaseprio_irq(stcb, sem); } else { nxsem_restorebaseprio_task(stcb, sem); } } /**************************************************************************** * Name: nxsem_canceled * * Description: * Called from nxsem_wait_irq() after a thread that was waiting for a semaphore * count was awakened because of a signal and the semaphore wait has been * cancelled. This function restores the correct thread priority of each * holder of the semaphore. * * Input Parameters: * sem - A reference to the semaphore no longer being waited for * * Returned Value: * None * * Assumptions: * ****************************************************************************/ void nxsem_canceled(FAR struct tcb_s *stcb, FAR sem_t *sem) { /* Check our assumptions */ DEBUGASSERT(sem->semcount <= 0); /* Adjust the priority of every holder as necessary */ nxsem_foreachholder(sem, nxsem_restoreholderprioall, stcb); } /**************************************************************************** * Name: sem_enumholders * * Description: * Show information about threads currently waiting on this semaphore * * Input Parameters: * sem - A reference to the semaphore * * Returned Value: * None * * Assumptions: * ****************************************************************************/ #if defined(CONFIG_DEBUG_FEATURES) && defined(CONFIG_SEM_PHDEBUG) void sem_enumholders(FAR sem_t *sem) { #ifdef CONFIG_DEBUG_INFO nxsem_foreachholder(sem, nxsem_dumpholder, NULL); #endif } #endif /**************************************************************************** * Name: nxsem_nfreeholders * * Description: * Return the number of available holder containers. This is a good way * to find out which threads are not calling sem_destroy. * * Input Parameters: * sem - A reference to the semaphore * * Returned Value: * The number of available holder containers * * Assumptions: * ****************************************************************************/ #if defined(CONFIG_DEBUG_FEATURES) && defined(CONFIG_SEM_PHDEBUG) int nxsem_nfreeholders(void) { #if CONFIG_SEM_PREALLOCHOLDERS > 0 FAR struct semholder_s *pholder; int n; for (pholder = g_freeholders, n = 0; pholder; pholder = pholder->flink) { n++; } return n; #else return 0; #endif } #endif #endif /* CONFIG_PRIORITY_INHERITANCE */