From: Rémi Denis-Courmont Date: Wed, 7 May 2008 20:12:52 +0000 (+0300) Subject: Use a per-object spin around the reference count. X-Git-Tag: 0.9.0-test0~1074 X-Git-Url: https://git.sesse.net/?a=commitdiff_plain;h=b3c8d478e9091fe55a2513eb8e416162da3bb5e4;p=vlc Use a per-object spin around the reference count. So we don't contend for the global structure lock all the time. --- diff --git a/src/libvlc.h b/src/libvlc.h index 6df516b3d0..0da4d2f574 100644 --- a/src/libvlc.h +++ b/src/libvlc.h @@ -187,6 +187,7 @@ struct vlc_object_internals_t vlc_spinlock_t spin; /* Objects management */ + vlc_spinlock_t ref_spin; unsigned i_refcount; vlc_destructor_t pf_destructor; bool b_attached; diff --git a/src/misc/objects.c b/src/misc/objects.c index 79381e5bb8..1f0193e5d2 100644 --- a/src/misc/objects.c +++ b/src/misc/objects.c @@ -89,7 +89,6 @@ static int CountChildren ( vlc_object_t *, int ); static void ListChildren ( vlc_list_t *, vlc_object_t *, int ); static void vlc_object_destroy( vlc_object_t *p_this ); -static void vlc_object_yield_locked( vlc_object_t *p_this ); /***************************************************************************** * Local structure lock @@ -169,6 +168,7 @@ void *vlc_custom_create( vlc_object_t *p_this, size_t i_size, } } + vlc_spin_init( &p_priv->ref_spin ); p_priv->i_refcount = 1; p_priv->pf_destructor = kVLCDestructor; p_priv->b_thread = false; @@ -187,7 +187,6 @@ void *vlc_custom_create( vlc_object_t *p_this, size_t i_size, vlc_mutex_lock( &structure_lock ); p_new->i_object_id = p_libvlc_global->i_counter++; - /* Wooohaa! If *this* fails, we're in serious trouble! Anyway it's * useless to try and recover anything if pp_objects gets smashed. */ TAB_APPEND( p_libvlc_global->i_objects, p_libvlc_global->pp_objects, @@ -424,6 +423,7 @@ static void vlc_object_destroy( vlc_object_t *p_this ) CloseHandle(p_priv->thread_id.hThread); #endif + vlc_spin_destroy( &p_priv->ref_spin ); vlc_mutex_destroy( &p_this->object_lock ); vlc_cond_destroy( &p_this->object_wait ); vlc_spin_destroy( &p_priv->spin ); @@ -713,7 +713,7 @@ void * vlc_object_get( int i_id ) /* This happens when there are only two remaining objects */ if( pp_objects[i_middle+1]->i_object_id == i_id ) { - vlc_object_yield_locked( pp_objects[i_middle+1] ); + vlc_object_yield( pp_objects[i_middle+1] ); obj = pp_objects[i_middle+1]; } break; @@ -721,7 +721,7 @@ void * vlc_object_get( int i_id ) } else { - vlc_object_yield_locked( pp_objects[i_middle] ); + vlc_object_yield( pp_objects[i_middle] ); vlc_mutex_unlock( &structure_lock ); return pp_objects[i_middle]; } @@ -749,7 +749,7 @@ void * __vlc_object_find( vlc_object_t *p_this, int i_type, int i_mode ) /* If we are of the requested type ourselves, don't look further */ if( !(i_mode & FIND_STRICT) && p_this->i_object_type == i_type ) { - vlc_object_yield_locked( p_this ); + vlc_object_yield( p_this ); vlc_mutex_unlock( &structure_lock ); return p_this; } @@ -797,15 +797,12 @@ void * __vlc_object_find_name( vlc_object_t *p_this, const char *psz_name, vlc_mutex_lock( &structure_lock ); - /* Avoid obvious freed object uses */ - assert( vlc_internals( p_this )->i_refcount > 0 ); - /* If have the requested name ourselves, don't look further */ if( !(i_mode & FIND_STRICT) && p_this->psz_object_name && !strcmp( p_this->psz_object_name, psz_name ) ) { - vlc_object_yield_locked( p_this ); + vlc_object_yield( p_this ); vlc_mutex_unlock( &structure_lock ); return p_this; } @@ -841,54 +838,58 @@ void * __vlc_object_find_name( vlc_object_t *p_this, const char *psz_name, } /** - **************************************************************************** - * increment an object refcount - *****************************************************************************/ - -/* When the structure_lock is locked */ -static void vlc_object_yield_locked( vlc_object_t *p_this ) + * Increment an object reference counter. + */ +void __vlc_object_yield( vlc_object_t *p_this ) { - vlc_assert_locked (&structure_lock); + vlc_object_internals_t *internals = vlc_internals( p_this ); + vlc_spin_lock( &internals->ref_spin ); /* Avoid obvious freed object uses */ - assert( vlc_internals( p_this )->i_refcount > 0 ); - + assert( internals->i_refcount > 0 ); /* Increment the counter */ - vlc_internals( p_this )->i_refcount++; -} - -/* Public function */ -void __vlc_object_yield( vlc_object_t *p_this ) -{ - vlc_mutex_lock( &structure_lock ); - vlc_object_yield_locked( p_this ); - vlc_mutex_unlock( &structure_lock ); + internals->i_refcount++; + vlc_spin_unlock( &internals->ref_spin ); } - /***************************************************************************** * decrement an object refcount * And destroy the object if its refcount reach zero. *****************************************************************************/ void __vlc_object_release( vlc_object_t *p_this ) { + vlc_object_internals_t *internals = vlc_internals( p_this ); bool b_should_destroy; - vlc_mutex_lock( &structure_lock ); + vlc_spin_lock( &internals->ref_spin ); + assert( internals->i_refcount > 0 ); - assert( vlc_internals( p_this )->i_refcount > 0 ); - vlc_internals( p_this )->i_refcount--; - b_should_destroy = (vlc_internals( p_this )->i_refcount == 0); + if( internals->i_refcount > 1 ) + { + /* Fast path */ + /* There are still other references to the object */ + internals->i_refcount--; + vlc_spin_unlock( &internals->ref_spin ); + return; + } + vlc_spin_unlock( &internals->ref_spin ); + + /* Slow path */ + /* Remember that we cannot hold the spin while waiting on the mutex */ + vlc_mutex_lock( &structure_lock ); + /* Take the spin again. Note that another thread may have yielded the + * object in the (very short) mean time. */ + vlc_spin_lock( &internals->ref_spin ); + b_should_destroy = --internals->i_refcount == 0; + vlc_spin_unlock( &internals->ref_spin ); if( b_should_destroy ) { - /* Make sure this object can't be obtained via vlc_find_object now that - * it is freed */ + /* Remove the object from the table so that it cannot be returned from + * vlc_object_find() and friends. */ libvlc_global_data_t *p_libvlc_global = vlc_global(); int i_index; - /* Wooohaa! If *this* fails, we're in serious trouble! Anyway it's - * useless to try and recover anything if pp_objects gets smashed. */ i_index = FindIndex( p_this, p_libvlc_global->pp_objects, p_libvlc_global->i_objects ); REMOVE_ELEM( p_libvlc_global->pp_objects, @@ -914,9 +915,6 @@ void __vlc_object_attach( vlc_object_t *p_this, vlc_object_t *p_parent ) vlc_mutex_lock( &structure_lock ); - /* Avoid obvious freed object uses */ - assert( vlc_internals( p_this )->i_refcount > 0 ); - /* Attach the parent to its child */ p_this->p_parent = p_parent; @@ -1299,7 +1297,7 @@ static vlc_object_t * FindObject( vlc_object_t *p_this, int i_type, int i_mode ) { if( p_tmp->i_object_type == i_type ) { - vlc_object_yield_locked( p_tmp ); + vlc_object_yield( p_tmp ); return p_tmp; } else @@ -1315,7 +1313,7 @@ static vlc_object_t * FindObject( vlc_object_t *p_this, int i_type, int i_mode ) p_tmp = p_this->pp_children[i]; if( p_tmp->i_object_type == i_type ) { - vlc_object_yield_locked( p_tmp ); + vlc_object_yield( p_tmp ); return p_tmp; } else if( p_tmp->i_children ) @@ -1353,7 +1351,7 @@ static vlc_object_t * FindObjectName( vlc_object_t *p_this, if( p_tmp->psz_object_name && !strcmp( p_tmp->psz_object_name, psz_name ) ) { - vlc_object_yield_locked( p_tmp ); + vlc_object_yield( p_tmp ); return p_tmp; } else @@ -1370,7 +1368,7 @@ static vlc_object_t * FindObjectName( vlc_object_t *p_this, if( p_tmp->psz_object_name && !strcmp( p_tmp->psz_object_name, psz_name ) ) { - vlc_object_yield_locked( p_tmp ); + vlc_object_yield( p_tmp ); return p_tmp; } else if( p_tmp->i_children ) @@ -1571,7 +1569,7 @@ static void ListReplace( vlc_list_t *p_list, vlc_object_t *p_object, return; } - vlc_object_yield_locked( p_object ); + vlc_object_yield( p_object ); p_list->p_values[i_index].p_object = p_object; @@ -1593,7 +1591,7 @@ static void ListReplace( vlc_list_t *p_list, vlc_object_t *p_object, return; } - vlc_object_yield_locked( p_object ); + vlc_object_yield( p_object ); p_list->p_values[p_list->i_count].p_object = p_object; p_list->i_count++;