/**************************************************************************** * mm/mm_heap/mm_sem.c * * Copyright (C) 2007-2009, 2013, 2017 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 #include /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /* Internal nxsem_* interfaces are not available in the user space in * PROTECTED and KERNEL builds. In that context, the application semaphore * interfaces must be used. The differences between the two sets of * interfaces are: (1) the nxsem_* interfaces do not cause cancellation * points and (2) they do not modify the errno variable. * * See additional definitions in include/nuttx/semaphore.h * * REVISIT: The fact that sem_wait() is a cancellation point is an issue * and does cause a violation: It makes all of the memory management * interfaces into cancellation points when used from user space in the * PROTECTED and KERNEL builds. */ #if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__) # define _SEM_GETERROR(r) #else # define _SEM_GETERROR(r) (r) = -errno #endif /* Define the following to enable semaphore state monitoring */ //#define MONITOR_MM_SEMAPHORE 1 #ifdef MONITOR_MM_SEMAPHORE # include # define msemerr _err # define msemwarn _warn # define mseminfo _info #else # ifdef CONFIG_CPP_HAVE_VARARGS # define msemerr(x...) # define msemwarn(x...) # define mseminfo(x...) # else # define msemerr (void) # define msemwarn (void) # define mseminfo (void) # endif #endif /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: mm_seminitialize * * Description: * Initialize the MM mutex * ****************************************************************************/ void mm_seminitialize(FAR struct mm_heap_s *heap) { /* Initialize the MM semaphore to one (to support one-at-a-time access to * private data sets). */ (void)nxsem_init(&heap->mm_semaphore, 0, 1); heap->mm_holder = -1; heap->mm_counts_held = 0; } /**************************************************************************** * Name: mm_trysemaphore * * Description: * Try to take the MM mutex. This is called only from the OS in certain * conditions when it is necessary to have exclusive access to the memory * manager but it is impossible to wait on a semaphore (e.g., the idle * process when it performs its background memory cleanup). * ****************************************************************************/ int mm_trysemaphore(FAR struct mm_heap_s *heap) { pid_t my_pid = getpid(); int ret; /* Do I already have the semaphore? */ if (heap->mm_holder == my_pid) { /* Yes, just increment the number of references that I have */ heap->mm_counts_held++; return OK; } else { /* Try to take the semaphore (perhaps waiting) */ ret = _SEM_TRYWAIT(&heap->mm_semaphore); if (ret < 0) { _SEM_GETERROR(ret); return ret; } /* We have it. Claim the heap and return */ heap->mm_holder = my_pid; heap->mm_counts_held = 1; return OK; } } /**************************************************************************** * Name: mm_takesemaphore * * Description: * Take the MM mutex. This is the normal action before all memory * management actions. * ****************************************************************************/ void mm_takesemaphore(FAR struct mm_heap_s *heap) { pid_t my_pid = getpid(); /* Do I already have the semaphore? */ if (heap->mm_holder == my_pid) { /* Yes, just increment the number of references that I have */ heap->mm_counts_held++; } else { int ret; /* Take the semaphore (perhaps waiting) */ mseminfo("PID=%d taking\n", my_pid); do { ret = _SEM_WAIT(&heap->mm_semaphore); /* The only case that an error should occur here is if the wait * was awakened by a signal. */ if (ret < 0) { #if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__) DEBUGASSERT(ret == -EINTR); #else int errcode = errno; DEBUGASSERT(errcode == EINTR); ret = -errcode; #endif } } while (ret == -EINTR); /* We have it (or some awful, unexpected error occurred). Claim * the semaphore and return. */ heap->mm_holder = my_pid; heap->mm_counts_held = 1; } mseminfo("Holder=%d count=%d\n", heap->mm_holder, heap->mm_counts_held); } /**************************************************************************** * Name: mm_givesemaphore * * Description: * Release the MM mutex when it is not longer needed. * ****************************************************************************/ void mm_givesemaphore(FAR struct mm_heap_s *heap) { #if defined(CONFIG_DEBUG_ASSERTIONS) || \ (defined(MONITOR_MM_SEMAPHORE) && defined(CONFIG_DEBUG_INFO)) pid_t my_pid = getpid(); #endif /* I better be holding at least one reference to the semaphore */ DEBUGASSERT(heap->mm_holder == my_pid); /* Do I hold multiple references to the semphore */ if (heap->mm_counts_held > 1) { /* Yes, just release one count and return */ heap->mm_counts_held--; mseminfo("Holder=%d count=%d\n", heap->mm_holder, heap->mm_counts_held); } else { /* Nope, this is the last reference I have */ mseminfo("PID=%d giving\n", my_pid); heap->mm_holder = -1; heap->mm_counts_held = 0; DEBUGVERIFY(_SEM_POST(&heap->mm_semaphore)); } }