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Diffstat (limited to 'nuttx/mm/mm_heap/mm_sem.c')
| -rw-r--r-- | nuttx/mm/mm_heap/mm_sem.c | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/nuttx/mm/mm_heap/mm_sem.c b/nuttx/mm/mm_heap/mm_sem.c new file mode 100644 index 000000000..baec83732 --- /dev/null +++ b/nuttx/mm/mm_heap/mm_sem.c @@ -0,0 +1,223 @@ +/**************************************************************************** + * mm/mm_heap/mm_sem.c + * + * Copyright (C) 2007-2009, 2013 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * 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 <unistd.h> +#include <errno.h> +#include <assert.h> + +#include <nuttx/mm.h> + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +/* Define the following to enable semaphore state monitoring */ +//#define MONITOR_MM_SEMAPHORE 1 + +#ifdef MONITOR_MM_SEMAPHORE +# ifdef CONFIG_DEBUG +# include <debug.h> +# define msemdbg dbg +# else +# define msemdbg printf +# endif +#else +# ifdef CONFIG_CPP_HAVE_VARARGS +# define msemdbg(x...) +# else +# define msemdbg (void) +# endif +#endif + +/**************************************************************************** + * Private Data + ****************************************************************************/ + +/**************************************************************************** + * 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)sem_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(); + + /* 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) */ + + if (sem_trywait(&heap->mm_semaphore) != 0) + { + return ERROR; + } + + /* We have it. Claim the stak 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 + { + /* Take the semaphore (perhaps waiting) */ + + msemdbg("PID=%d taking\n", my_pid); + while (sem_wait(&heap->mm_semaphore) != 0) + { + /* The only case that an error should occur here is if + * the wait was awakened by a signal. + */ + + ASSERT(errno == EINTR); + } + + /* We have it. Claim the stake and return */ + + heap->mm_holder = my_pid; + heap->mm_counts_held = 1; + } + + msemdbg("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) +{ +#ifdef CONFIG_DEBUG + 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--; + msemdbg("Holder=%d count=%d\n", heap->mm_holder, heap->mm_counts_held); + } + else + { + /* Nope, this is the last reference I have */ + +#ifdef CONFIG_DEBUG + msemdbg("PID=%d giving\n", my_pid); +#endif + + heap->mm_holder = -1; + heap->mm_counts_held = 0; + ASSERT(sem_post(&heap->mm_semaphore) == 0); + } +} + |