630 lines
25 KiB
C
630 lines
25 KiB
C
/****************************************************************************
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* include/nuttx/semaphore.h
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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#ifndef __INCLUDE_NUTTX_SEMAPHORE_H
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#define __INCLUDE_NUTTX_SEMAPHORE_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <errno.h>
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#include <semaphore.h>
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#include <nuttx/clock.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Most internal nxsem_* interfaces are not available in the user space in
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* PROTECTED and KERNEL builds. In that context, the application semaphore
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* interfaces must be used. The differences between the two sets of
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* interfaces are: (1) the nxsem_* interfaces do not cause cancellation
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* points and (2) they do not modify the errno variable.
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*
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* This is only important when compiling libraries (libc or libnx) that are
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* used both by the OS (libkc.a and libknx.a) or by the applications
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* (libc.a and libnx.a). In that case, the correct interface must be
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* used for the build context.
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*
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* REVISIT: In the flat build, the same functions must be used both by
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* the OS and by applications. We have to use the normal user functions
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* in this case or we will fail to set the errno or fail to create the
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* cancellation point.
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*/
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#if !defined(CONFIG_BUILD_FLAT) && defined(__KERNEL__)
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# define _SEM_INIT(s,p,c) nxsem_init(s,p,c)
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# define _SEM_DESTROY(s) nxsem_destroy(s)
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# define _SEM_WAIT(s) nxsem_wait(s)
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# define _SEM_TRYWAIT(s) nxsem_trywait(s)
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# define _SEM_TIMEDWAIT(s,t) nxsem_timedwait(s,t)
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# define _SEM_CLOCKWAIT(s,c,t) nxsem_clockwait(s,c,t)
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# define _SEM_POST(s) nxsem_post(s)
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# define _SEM_GETVALUE(s,v) nxsem_get_value(s,v)
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# define _SEM_GETPROTOCOL(s,p) nxsem_get_protocol(s,p)
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# define _SEM_SETPROTOCOL(s,p) nxsem_set_protocol(s,p)
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# define _SEM_ERRNO(r) (-(r))
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# define _SEM_ERRVAL(r) (r)
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#else
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# define _SEM_INIT(s,p,c) sem_init(s,p,c)
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# define _SEM_DESTROY(s) sem_destroy(s)
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# define _SEM_WAIT(s) sem_wait(s)
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# define _SEM_TRYWAIT(s) sem_trywait(s)
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# define _SEM_TIMEDWAIT(s,t) sem_timedwait(s,t)
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# define _SEM_CLOCKWAIT(s,c,t) sem_clockwait(s,c,t)
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# define _SEM_GETVALUE(s,v) sem_getvalue(s,v)
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# define _SEM_POST(s) sem_post(s)
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# define _SEM_GETPROTOCOL(s,p) sem_getprotocol(s,p)
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# define _SEM_SETPROTOCOL(s,p) sem_setprotocol(s,p)
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# define _SEM_ERRNO(r) errno
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# define _SEM_ERRVAL(r) (-errno)
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#endif
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/****************************************************************************
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* Public Type Definitions
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****************************************************************************/
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#ifdef CONFIG_FS_NAMED_SEMAPHORES
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/* This is the named semaphore inode */
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struct inode;
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struct nsem_inode_s
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{
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/* This must be the first element of the structure. In sem_close() this
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* structure must be cast compatible with sem_t.
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*/
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sem_t ns_sem; /* The contained semaphore */
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/* Inode payload unique to named semaphores. */
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FAR struct inode *ns_inode; /* Containing inode */
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};
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#endif
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/****************************************************************************
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* Public Data
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****************************************************************************/
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#ifndef __ASSEMBLY__
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#ifdef __cplusplus
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#define EXTERN extern "C"
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extern "C"
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{
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#else
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#define EXTERN extern
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#endif
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Name: nxsem_init
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*
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* Description:
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* This function initializes the UNNAMED semaphore sem. Following a
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* successful call to nxsem_init(), the semaphore may be used in subsequent
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* calls to nxsem_wait(), nxsem_post(), and nxsem_trywait(). The semaphore
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* remains usable until it is destroyed.
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*
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* Only sem itself may be used for performing synchronization. The result
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* of referring to copies of sem in calls to sem_wait(), sem_trywait(),
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* sem_post(), and sem_destroy() is undefined.
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*
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* Input Parameters:
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* sem - Semaphore to be initialized
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* pshared - Process sharing (not used)
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* value - Semaphore initialization value
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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int nxsem_init(FAR sem_t *sem, int pshared, unsigned int value);
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/****************************************************************************
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* Name: nxsem_destroy
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*
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* Description:
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* This function is used to destroy the un-named semaphore indicated by
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* 'sem'. Only a semaphore that was created using nxsem_init() may be
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* destroyed using nxsem_destroy(); the effect of calling nxsem_destroy()
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* with a named semaphore is undefined. The effect of subsequent use of
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* the semaphore sem is undefined until sem is re-initialized by another
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* call to nxsem_init().
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*
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* The effect of destroying a semaphore upon which other processes are
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* currently blocked is undefined.
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*
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* Input Parameters:
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* sem - Semaphore to be destroyed.
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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int nxsem_destroy(FAR sem_t *sem);
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/****************************************************************************
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* Name: nxsem_wait
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*
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* Description:
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* This function attempts to lock the semaphore referenced by 'sem'. If
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* the semaphore value is (<=) zero, then the calling task will not return
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* until it successfully acquires the lock.
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*
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* This is an internal OS interface. It is functionally equivalent to
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* sem_wait except that:
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*
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* - It is not a cancellation point, and
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* - It does not modify the errno value.
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*
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* Input Parameters:
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* sem - Semaphore descriptor.
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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* Possible returned errors:
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*
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* EINVAL - Invalid attempt to get the semaphore
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* EINTR - The wait was interrupted by the receipt of a signal.
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*
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****************************************************************************/
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int nxsem_wait(FAR sem_t *sem);
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/****************************************************************************
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* Name: nxsem_trywait
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*
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* Description:
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* This function locks the specified semaphore only if the semaphore is
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* currently not locked. Otherwise, it locks the semaphore. In either
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* case, the call returns without blocking.
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*
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* Input Parameters:
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* sem - the semaphore descriptor
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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* Possible returned errors:
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*
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* EINVAL - Invalid attempt to get the semaphore
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* EAGAIN - The semaphore is not available.
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*
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* Assumptions:
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*
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****************************************************************************/
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int nxsem_trywait(FAR sem_t *sem);
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/****************************************************************************
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* Name: nxsem_timedwait
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*
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* Description:
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* This function will lock the semaphore referenced by sem as in the
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* sem_wait() function. However, if the semaphore cannot be locked without
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* waiting for another process or thread to unlock the semaphore by
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* performing a sem_post() function, this wait will be terminated when the
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* specified timeout expires.
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*
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* The timeout will expire when the absolute time specified by abstime
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* passes, as measured by the clock on which timeouts are based (that is,
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* when the value of that clock equals or exceeds abstime), or if the
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* absolute time specified by abstime has already been passed at the
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* time of the call.
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*
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* This is an internal OS interface. It is functionally equivalent to
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* sem_wait except that:
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*
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* - It is not a cancellation point, and
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* - It does not modify the errno value.
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*
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* Input Parameters:
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* sem - Semaphore object
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* abstime - The absolute time to wait until a timeout is declared.
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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* That may be one of:
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*
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* EINVAL The sem argument does not refer to a valid semaphore. Or the
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* thread would have blocked, and the abstime parameter specified
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* a nanoseconds field value less than zero or greater than or
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* equal to 1000 million.
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* ETIMEDOUT The semaphore could not be locked before the specified timeout
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* expired.
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* EDEADLK A deadlock condition was detected.
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* EINTR A signal interrupted this function.
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* ECANCELED May be returned if the thread is canceled while waiting.
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*
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****************************************************************************/
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int nxsem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime);
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/****************************************************************************
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* Name: nxsem_clockwait
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*
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* Description:
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* This function will lock the semaphore referenced by sem as in the
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* sem_wait() function. However, if the semaphore cannot be locked without
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* waiting for another process or thread to unlock the semaphore by
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* performing a sem_post() function, this wait will be terminated when the
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* specified timeout expires.
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*
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* The timeout will expire when the absolute time specified by abstime
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* passes, as measured by the clock on which timeouts are based (that is,
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* when the value of that clock equals or exceeds abstime), or if the
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* absolute time specified by abstime has already been passed at the
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* time of the call.
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*
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* This is an internal OS interface. It is functionally equivalent to
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* sem_wait except that:
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*
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* - It is not a cancellation point, and
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* - It does not modify the errno value.
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*
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* Input Parameters:
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* sem - Semaphore object
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* clockid - The timing source to use in the conversion
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* abstime - The absolute time to wait until a timeout is declared.
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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* That may be one of:
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*
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* EINVAL The sem argument does not refer to a valid semaphore. Or the
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* thread would have blocked, and the abstime parameter specified
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* a nanoseconds field value less than zero or greater than or
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* equal to 1000 million.
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* ETIMEDOUT The semaphore could not be locked before the specified timeout
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* expired.
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* EDEADLK A deadlock condition was detected.
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* EINTR A signal interrupted this function.
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* ECANCELED May be returned if the thread is canceled while waiting.
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*
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****************************************************************************/
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int nxsem_clockwait(FAR sem_t *sem, clockid_t clockid,
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FAR const struct timespec *abstime);
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/****************************************************************************
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* Name: nxsem_tickwait
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*
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* Description:
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* This function is a lighter weight version of sem_timedwait(). It is
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* non-standard and intended only for use within the RTOS.
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*
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* Input Parameters:
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* sem - Semaphore object
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* start - The system time that the delay is relative to. If the
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* current time is not the same as the start time, then the
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* delay will be adjust so that the end time will be the same
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* in any event.
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* delay - Ticks to wait from the start time until the semaphore is
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* posted. If ticks is zero, then this function is equivalent
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* to sem_trywait().
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*
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* Returned Value:
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* This is an internal OS interface, not available to applications, and
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* hence follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure:
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*
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* -ETIMEDOUT is returned on the timeout condition.
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* -ECANCELED may be returned if the thread is canceled while waiting.
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*
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****************************************************************************/
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int nxsem_tickwait(FAR sem_t *sem, clock_t start, uint32_t delay);
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/****************************************************************************
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* Name: nxsem_post
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*
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* Description:
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* When a kernel thread has finished with a semaphore, it will call
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* nxsem_post(). This function unlocks the semaphore referenced by sem
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* by performing the semaphore unlock operation on that semaphore.
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*
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* If the semaphore value resulting from this operation is positive, then
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* no tasks were blocked waiting for the semaphore to become unlocked; the
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* semaphore is simply incremented.
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*
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* If the value of the semaphore resulting from this operation is zero,
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* then one of the tasks blocked waiting for the semaphore shall be
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* allowed to return successfully from its call to sem_wait().
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*
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* Input Parameters:
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* sem - Semaphore descriptor
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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* Assumptions:
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* This function may be called from an interrupt handler.
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*
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****************************************************************************/
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int nxsem_post(FAR sem_t *sem);
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/****************************************************************************
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* Name: nxsem_get_value
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*
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* Description:
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* This function updates the location referenced by 'sval' argument to
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* have the value of the semaphore referenced by 'sem' without effecting
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* the state of the semaphore. The updated value represents the actual
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* semaphore value that occurred at some unspecified time during the call,
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* but may not reflect the actual value of the semaphore when it is
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* returned to the calling task.
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*
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* If 'sem' is locked, the value return by nxsem_get_value() will either be
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* zero or a negative number whose absolute value represents the number
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* of tasks waiting for the semaphore.
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*
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* Input Parameters:
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* sem - Semaphore descriptor
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* sval - Buffer by which the value is returned
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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int nxsem_get_value(FAR sem_t *sem, FAR int *sval);
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/****************************************************************************
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* Name: nxsem_reset
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*
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* Description:
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* Reset a semaphore count to a specific value. This is similar to part
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* of the operation of nxsem_init(). But nxsem_reset() may need to wake up
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* tasks waiting on a count. This kind of operation is sometimes required
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* within the OS (only) for certain error handling conditions.
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*
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* Input Parameters:
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* sem - Semaphore descriptor to be reset
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* count - The requested semaphore count
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*
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* Returned Value:
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* This is an internal OS interface, not available to applications, and
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* hence follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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int nxsem_reset(FAR sem_t *sem, int16_t count);
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/****************************************************************************
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* Name: nxsem_get_protocol
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*
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* Description:
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* Return the value of the semaphore protocol attribute.
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*
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* Input Parameters:
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* sem - A pointer to the semaphore whose attributes are to be
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* queried.
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* protocol - The user provided location in which to store the protocol
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* value.
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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#define nxsem_get_protocol(s,p) sem_getprotocol(s,p)
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/****************************************************************************
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* Name: nxsem_set_protocol
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*
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* Description:
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* Set semaphore protocol attribute.
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*
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* One particularly important use of this function is when a semaphore
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* is used for inter-task communication like:
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*
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* TASK A TASK B
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* sem_init(sem, 0, 0);
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* sem_wait(sem);
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* sem_post(sem);
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* Awakens as holder
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*
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* In this case priority inheritance can interfere with the operation of
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* the semaphore. The problem is that when TASK A is restarted it is a
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* holder of the semaphore. However, it never calls sem_post(sem) so it
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* becomes *permanently* a holder of the semaphore and may have its
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* priority boosted when any other task tries to acquire the semaphore.
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*
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* The fix is to call nxsem_set_protocol(SEM_PRIO_NONE) immediately after
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* the sem_init() call so that there will be no priority inheritance
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* operations on this semaphore.
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*
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* Input Parameters:
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* sem - A pointer to the semaphore whose attributes are to be
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* modified
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* protocol - The new protocol to use
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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int nxsem_set_protocol(FAR sem_t *sem, int protocol);
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/****************************************************************************
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* Name: nxsem_wait_uninterruptible
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*
|
|
* Description:
|
|
* This function is wrapped version of nxsem_wait(), which is
|
|
* uninterruptible and convenient for use.
|
|
*
|
|
* Parameters:
|
|
* sem - Semaphore descriptor.
|
|
*
|
|
* Return Value:
|
|
* Zero(OK) - On success
|
|
* EINVAL - Invalid attempt to get the semaphore
|
|
* ECANCELED - May be returned if the thread is canceled while waiting.
|
|
*
|
|
* NOTE: It is essential that callers of this function handle the
|
|
* ECANCELED error. Correct handling is that the function should return the
|
|
* error and the error should propagate back up the calling tree to the
|
|
* cancellation point interface function where the thread termination will
|
|
* be handled gracefully
|
|
*
|
|
****************************************************************************/
|
|
|
|
int nxsem_wait_uninterruptible(FAR sem_t *sem);
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_timedwait_uninterruptible
|
|
*
|
|
* Description:
|
|
* This function is wrapped version of nxsem_timedwait(), which is
|
|
* uninterruptible and convenient for use.
|
|
*
|
|
* Input Parameters:
|
|
* sem - Semaphore object
|
|
* abstime - The absolute time to wait until a timeout is declared.
|
|
*
|
|
* Returned Value:
|
|
* EINVAL The sem argument does not refer to a valid semaphore. Or the
|
|
* thread would have blocked, and the abstime parameter specified
|
|
* a nanoseconds field value less than zero or greater than or
|
|
* equal to 1000 million.
|
|
* ETIMEDOUT The semaphore could not be locked before the specified timeout
|
|
* expired.
|
|
* EDEADLK A deadlock condition was detected.
|
|
* ECANCELED May be returned if the thread is canceled while waiting.
|
|
*
|
|
* NOTE: It is essential that callers of this function handle the
|
|
* ECANCELED error. Correct handling is that the function should return the
|
|
* error and the error should propagate back up the calling tree to the
|
|
* cancellation point interface function where the thread termination will
|
|
* be handled gracefully
|
|
*
|
|
****************************************************************************/
|
|
|
|
int nxsem_timedwait_uninterruptible(FAR sem_t *sem,
|
|
FAR const struct timespec *abstime);
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_clockwait_uninterruptible
|
|
*
|
|
* Description:
|
|
* This function is wrapped version of nxsem_timedwait(), which is
|
|
* uninterruptible and convenient for use.
|
|
*
|
|
* Input Parameters:
|
|
* sem - Semaphore object
|
|
* clockid - The timing source to use in the conversion
|
|
* abstime - The absolute time to wait until a timeout is declared.
|
|
*
|
|
* Returned Value:
|
|
* EINVAL The sem argument does not refer to a valid semaphore. Or the
|
|
* thread would have blocked, and the abstime parameter specified
|
|
* a nanoseconds field value less than zero or greater than or
|
|
* equal to 1000 million.
|
|
* ETIMEDOUT The semaphore could not be locked before the specified timeout
|
|
* expired.
|
|
* EDEADLK A deadlock condition was detected.
|
|
* ECANCELED May be returned if the thread is canceled while waiting.
|
|
*
|
|
* NOTE: It is essential that callers of this function handle the
|
|
* ECANCELED error. Correct handling is that the function should return the
|
|
* error and the error should propagate back up the calling tree to the
|
|
* cancellation point interface function where the thread termination will
|
|
* be handled gracefully
|
|
*
|
|
****************************************************************************/
|
|
|
|
int nxsem_clockwait_uninterruptible(FAR sem_t *sem, clockid_t clockid,
|
|
FAR const struct timespec *abstime);
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_tickwait_uninterruptible
|
|
*
|
|
* Description:
|
|
* This function is wrapped version of nxsem_tickwait(), which is
|
|
* uninterruptible and convenient for use.
|
|
*
|
|
* Input Parameters:
|
|
* sem - Semaphore object
|
|
* start - The system time that the delay is relative to. If the
|
|
* current time is not the same as the start time, then the
|
|
* delay will be adjust so that the end time will be the same
|
|
* in any event.
|
|
* delay - Ticks to wait from the start time until the semaphore is
|
|
* posted. If ticks is zero, then this function is equivalent
|
|
* to sem_trywait().
|
|
*
|
|
* Returned Value:
|
|
* This is an internal OS interface, not available to applications, and
|
|
* hence follows the NuttX internal error return policy: Zero (OK) is
|
|
* returned on success. A negated errno value is returned on failure:
|
|
*
|
|
* -ETIMEDOUT is returned on the timeout condition.
|
|
* -ECANCELED may be returned if the thread is canceled while waiting.
|
|
*
|
|
* NOTE: It is essential that callers of this function handle the
|
|
* ECANCELED error. Correct handling is that the function should return the
|
|
* error and the error should propagate back up the calling tree to the
|
|
* cancellation point interface function where the thread termination will
|
|
* be handled gracefully
|
|
*
|
|
****************************************************************************/
|
|
|
|
int nxsem_tickwait_uninterruptible(FAR sem_t *sem, clock_t start,
|
|
uint32_t delay);
|
|
|
|
#undef EXTERN
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
#endif /* __INCLUDE_NUTTX_SEMAPHORE_H */
|