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Diffstat (limited to 'src/ssx/ssx/ssx_semaphore_init.c')
-rwxr-xr-x | src/ssx/ssx/ssx_semaphore_init.c | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/src/ssx/ssx/ssx_semaphore_init.c b/src/ssx/ssx/ssx_semaphore_init.c new file mode 100755 index 0000000..98bba89 --- /dev/null +++ b/src/ssx/ssx/ssx_semaphore_init.c @@ -0,0 +1,84 @@ +// $Id: ssx_semaphore_init.c,v 1.2 2014/02/03 01:30:44 daviddu Exp $ +// $Source: /afs/awd/projects/eclipz/KnowledgeBase/.cvsroot/eclipz/chips/p8/working/procedures/ssx/ssx/ssx_semaphore_init.c,v $ +//----------------------------------------------------------------------------- +// *! (C) Copyright International Business Machines Corp. 2013 +// *! All Rights Reserved -- Property of IBM +// *! *** IBM Confidential *** +//----------------------------------------------------------------------------- + +/// \file ssx_semaphore_init.c +/// \brief SSX semaphore API initialization routines +/// +/// The entry points in this file are routines that are typically used during +/// initialization, and their code space could be deallocated and recovered if +/// no longer needed by the application after initialization. + +#include "ssx.h" + +/// Create (initialize) a semaphore +/// +/// \param semaphore A pointer to an SsxSemaphore structure to initialize +/// +/// \param initial_count The initial count of the semaphore +/// +/// \param max_count The maximum count allowed in the semaphore, for error +/// checking +/// +/// Semaphores are created (initialized) by a call of \c +/// ssx_semaphore_create(), using an application-provided instance of an \c +/// SsxSemaphore structure. This structure \e is the semaphore, so the +/// application must never modify the structure if the semaphore is in use. +/// SSX has no way to know if an \c SsxSemaphore structure provided to +/// \c ssx_semaphore_create() is safe to use as a semaphore, and will silently +/// modify whatever memory is provided. +/// +/// SSX provides two simple overflow semantics based on the value of max_count +/// in the call of \c ssx_semaphore_create(). +/// +/// If \a max_count = 0, then posting to the semaphore first increments the +/// internal count by 1. Overflows are ignored and will wrap the internal +/// count through 0. +/// +/// If \a max_count != 0, then posting to the semaphore first increments the +/// internal count by 1, wrapping through 0 in the event of overflow. If the +/// resulting count is greater than max_count, \c ssx_semaphore_post() will +/// return the error \c -SSX_SEMAPHORE_POST_OVERFLOW to the caller. +/// +/// In most applications it is probably best to use the \a max_count != 0 +/// semantics to trap programming errors, unless there is a specific +/// application where overflow is expected and ignorable. As a fine point of +/// the specification, a \a max_count of 0 is equivalent to a max_count of +/// 0xFFFFFFFF. +/// +/// Return values other then SSX_OK (0) are errors; see \ref ssx_errors +/// +/// \retval 0 Successful completion +/// +/// \retval -SSX_INVALID_SEMAPHORE_AT_CREATE The \a semaphore is a null (0) +/// pointer. +/// +/// \retval -SSX_INVALID_ARGUMENT_SEMAPHORE The \a max_count is non-zero +/// and less than the \a initial_count. + +int +ssx_semaphore_create(SsxSemaphore *semaphore, + SsxSemaphoreCount initial_count, + SsxSemaphoreCount max_count) +{ + if (SSX_ERROR_CHECK_API) { + SSX_ERROR_IF(semaphore == 0, SSX_INVALID_SEMAPHORE_AT_CREATE); + SSX_ERROR_IF((max_count != 0) && (initial_count > max_count), + SSX_INVALID_ARGUMENT_SEMAPHORE); + } + + __ssx_thread_queue_clear(&(semaphore->pending_threads)); + semaphore->count = initial_count; + semaphore->max_count = max_count; + + return SSX_OK; +} + + + + + |