/* * remote_sem.h - POSIX unnammed semaphore definition. * * Author Alain Greiner (2016) * * Copyright (c) UPMC Sorbonne Universites * * This file is part of ALMOS-MKH. * * ALMOS-MKH is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by * the Free Software Foundation; version 2.0 of the License. * * ALMOS-MKH is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with ALMOS-MKH; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ #ifndef _SEMAPHORE_H_ #define _SEMAPHORE_H_ #include #include #include /********************************************************************************************* * This file defines a POSIX compliant unnamed semaphore. * * A semaphore is declared by a given user process as a "sem_t" global variable. * The user "sem_t" structure is implemented as an unsigned long, but the value is not * used by the kernel. ALMOS-MKH uses only the sem_t virtual address as an identifier. * For each user semaphore, ALMOS-MKH creates a kernel "remote_sem_t" structure. * - This structure is allocated in the reference cluster by the sem_init() syscall, * and destroyed by the sem_destroy() syscall, using RPC if the calling thread is not * running in the reference cluster. * - The threads accessing the semaphore with the sem_get_value(), sem_wait(), sem_post() * syscalls can be running in any cluster, as these syscalls access the "remote_sem_t" * structure with remote_read / remote_write access functions. ********************************************************************************************/ /********************************************************************************************* * This structure defines the kernel semaphore descriptor. * - It contains the root of a waiting threads queue, implemented as a distributed xlist. * - It contains an xlist of all semaphores, rooted in the reference process descriptor. * - It contains a lock protecting both the semaphore value and the waiting queue. ********************************************************************************************/ typedef struct remote_sem_s { remote_spinlock_t lock; /*! lock protecting both count and wait_queue */ uint32_t count; /*! current value */ intptr_t ident; /*! virtual address in user space == identifier */ xlist_entry_t root; /*! root of waiting thread queue */ xlist_entry_t list; /*! member of list of semaphores in same process */ } remote_sem_t; /********************************************************************************************* * This function returns an extended pointer on the remote semaphore identified * by its virtual address in a given user process. It makes an associative search, * scanning the list of semaphores rooted in the reference process descriptor. ********************************************************************************************* * @ process : pointer on local process descriptor. * @ vaddr : semaphore virtual address, used as identifier. * @ returns extended pointer on semaphore if success / returns XPTR_NULL if not found. ********************************************************************************************/ xptr_t remote_sem_from_vaddr( intptr_t vaddr ); /********************************************************************************************* * This function implements the SEM_INIT operation. * It allocates memory for a remote semaphore in reference cluster, using a RPC if required, * and initializes it, using remote accesses from values defined by the and * arguments. It uses also a remote access to return the extended pointer on the semaphore * in the buffer identified by the argument. ********************************************************************************************* * @ vaddr : [in] semaphore virtual address, used as identifier. * @ value : [in] semaphore initial value. * @ sem_xp_xp : [out] extended pointer on buffer to store extended pointer on semaphore. * @ returns 0 if success / returns -1 if no memory. ********************************************************************************************/ error_t remote_sem_create( intptr_t vaddr, uint32_t value, xptr_t sem_xp_xp ); /****************************yy*************************************************************** * This function implements the SEM_DESTROY operation. * It desactivates the semaphore, and releases the physical memory allocated in the * reference cluster, using a RPC if required. ********************************************************************************************* * @ sem_xp : [in] extended pointer on semaphore. ********************************************************************************************/ void remote_sem_destroy( xptr_t sem_xp ); /****************************yy*************************************************************** * This blocking function implements the SEM_WAIT operation. * - It returns only when the remote semaphore has a non-zero value, * and has been atomically decremented. * - if the semaphore has a zero value, it register the calling thread in the semaphore * waiting queue, block the thread, and yield. ********************************************************************************************* * @ sem_xp : [in] extended pointer on semaphore. ********************************************************************************************/ void remote_sem_wait( xptr_t sem_xp ); /****************************yy*************************************************************** * This function mplements the SEM_POST operation. * - It atomically increments the remote semaphore if the semaphore waiting queue is empty. * - If the waiting queue is not empty, it wakes up the first waiting thread. ********************************************************************************************* * @ sem_xp : [in] extended pointer on semaphore. ********************************************************************************************/ void remote_sem_post( xptr_t sem_xp ); /****************************yy*************************************************************** * This function implements the SEM_GETVALUE operation. * It returns in the buffer the semaphore current value. ********************************************************************************************* * @ sem_xp : [in] extended pointer on semaphore. * @ data : [out] local pointer on buffer for returned value. ********************************************************************************************/ void remote_sem_get_value( xptr_t sem_xp, uint32_t * data ); #endif /* _SEMAPHORE_H_ */