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author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2007-02-17 23:21:28 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2007-02-17 23:21:28 +0000 |
commit | e3940eb2080711edac189cca3f642ee89dc215f2 (patch) | |
tree | 1c390958fae49e34dce698b175487e6d4681e540 /nuttx/mm/mm_sem.c | |
parent | 2223612deb2cc6322992f8595b6d6f86fcb53ae1 (diff) | |
download | px4-nuttx-e3940eb2080711edac189cca3f642ee89dc215f2.tar.gz px4-nuttx-e3940eb2080711edac189cca3f642ee89dc215f2.tar.bz2 px4-nuttx-e3940eb2080711edac189cca3f642ee89dc215f2.zip |
NuttX RTOS
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3 42af7a65-404d-4744-a932-0658087f49c3
Diffstat (limited to 'nuttx/mm/mm_sem.c')
-rw-r--r-- | nuttx/mm/mm_sem.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/nuttx/mm/mm_sem.c b/nuttx/mm/mm_sem.c new file mode 100644 index 000000000..be3a2c1b0 --- /dev/null +++ b/nuttx/mm/mm_sem.c @@ -0,0 +1,177 @@ +/************************************************************ + * mm_sem.c + * + * Copyright (C) 2007 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 Gregory Nutt 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 "mm_environment.h" +#include <unistd.h> +#include <semaphore.h> +#include <errno.h> +#include <assert.h> +#include "mm_internal.h" + +/************************************************************ + * 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 +# define msemdbg(x...) +#endif + +/************************************************************ + * Private Data + ************************************************************/ + +/* Mutually exclusive access to this data set is enforced with + * the following (un-named) semaphore. */ + +static sem_t g_mm_semaphore; +static pid_t g_holder; +static int g_counts_held; + +/************************************************************ + * Public Functions + ************************************************************/ + +/************************************************************ + * mm_seminitialize + ************************************************************/ + +void mm_seminitialize(void) +{ + /* Initialize the MM semaphore to one (to support one-at- + * a-time access to private data sets. + */ + + (void)sem_init(&g_mm_semaphore, 0, 1); + + g_holder = -1; + g_counts_held = 0; +} + +/************************************************************ + * mm_takesemaphore + ************************************************************/ + +void mm_takesemaphore(void) +{ + pid_t my_pid = getpid(); + + /* Do I already have the semaphore? */ + + if (g_holder == my_pid) + { + /* Yes, just increment the number of references that I have */ + + g_counts_held++; + } + else + { + /* Take the semaphore (perhaps waiting) */ + + msemdbg("%s: PID=%d taking\n", __FUNCTION__, my_pid); + while (sem_wait(&g_mm_semaphore) != 0) + { + /* The only case that an error should occur here is if + * the wait was awakened by a signal. + */ + + ASSERT(mm_errno == EINTR); + } + + /* We have it. Claim the stak and return */ + + g_holder = my_pid; + g_counts_held = 1; + } + + msemdbg("%s: Holder=%d count=%d\n", + __FUNCTION__, g_holder, g_counts_held); +} + +/************************************************************ + * mm_givesemaphore + ************************************************************/ + +void mm_givesemaphore(void) +{ + pid_t my_pid = getpid(); + + /* I better be holding at least one reference to the semaphore */ + + ASSERT(g_holder == my_pid); + + /* Do I hold multiple references to the semphore */ + + if (g_counts_held > 1) + { + /* Yes, just release one count and return */ + + g_counts_held--; + msemdbg("%s: Holder=%d count=%d\n", + __FUNCTION__, g_holder, g_counts_held); + } + else + { + /* Nope, this is the last reference I have */ + + msemdbg("%s: PID=%d giving\n", __FUNCTION__, my_pid); + g_holder = -1; + g_counts_held = 0; + ASSERT(sem_post(&g_mm_semaphore) == 0); + } +} + +#ifdef MM_TEST +int mm_getsemaphore(void) +{ + int sval; + sem_getvalue(&g_mm_semaphore, &sval); + return sval; +} +#endif + |