mono/sgen/sgen-copy-object.h

   1 /**
   2  * \file
   3  * This is where objects are copied.
   4  *
   5  * Copyright 2001-2003 Ximian, Inc
   6  * Copyright 2003-2010 Novell, Inc.
   7  * Copyright (C) 2012 Xamarin Inc
   8  *
   9  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
  10  */
  11
  12 /*
  13  * Defines
  14  *
  15  *     GCObject* copy_object_no_checks (GCObject *obj, SgenGrayQueue *queue)
  16  *
  17  * which allocates new space for `obj`, copies it there, forwards `obj` to its new location,
  18  * and enqueues the copy into `queue`.
  19  *
  20  * To be defined by the includer:
  21  *
  22  *     COLLECTOR_SERIAL_ALLOC_FOR_PROMOTION(vt, obj, objsize, has_refs)
  23  *
  24  * Allocates space for promoting object `obj`, with size `objsize`, and initizializes the
  25  * vtable with `vt`.  `has_refs` indicates whether the object contains references.
  26  *
  27  *     collector_pin_object(obj, queue)
  28  *
  29  * Called when no space for `obj` could be allocated.  It must pin `obj` and enqueue it into
  30  * `queue` for scanning.
  31  */
  32
  33 extern guint64 stat_copy_object_called_nursery;
  34 extern guint64 stat_objects_copied_nursery;
  35
  36 extern guint64 stat_nursery_copy_object_failed_from_space;
  37 extern guint64 stat_nursery_copy_object_failed_forwarded;
  38 extern guint64 stat_nursery_copy_object_failed_pinned;
  39
  40 extern guint64 stat_slots_allocated_in_vain;
  41
  42 /*
  43  * This function can be used even if the vtable of obj is not valid
  44  * anymore, which is the case in the parallel collector.
  45  */
  46 static MONO_ALWAYS_INLINE void
  47 par_copy_object_no_checks (char *destination, GCVTable vt, void *obj, mword objsize)
  48 {
  49         sgen_client_pre_copy_checks (destination, vt, obj, objsize);
  50         sgen_binary_protocol_copy (obj, destination, vt, objsize);
  51
  52         /* FIXME: assumes object layout */
  53         memcpy ((char*)destination + sizeof (mword), (char*)obj + sizeof (mword), objsize - sizeof (mword));
  54
  55         /* adjust array->bounds */
  56         SGEN_ASSERT (9, sgen_vtable_get_descriptor (vt), "vtable %p has no gc descriptor", vt);
  57
  58         sgen_client_update_copied_object (destination, vt, obj, objsize);
  59 }
  60
  61 /*
  62  * Copies an object and enqueues it if a queue is given.
  63  * This can return OBJ itself on OOM.
  64  */
  65 static MONO_NEVER_INLINE GCObject *
  66 copy_object_no_checks (GCObject *obj, SgenGrayQueue *queue)
  67 {
  68         GCVTable vt = SGEN_LOAD_VTABLE_UNCHECKED (obj);
  69         gboolean has_references = SGEN_VTABLE_HAS_REFERENCES (vt);
  70         mword objsize = SGEN_ALIGN_UP (sgen_client_par_object_get_size (vt, obj));
  71         void *destination = COLLECTOR_SERIAL_ALLOC_FOR_PROMOTION (vt, obj, objsize, has_references);
  72
  73         if (G_UNLIKELY (!destination)) {
  74                 /* FIXME: Is this path ever tested? */
  75                 collector_pin_object (obj, queue);
  76                 sgen_set_pinned_from_failed_allocation (objsize);
  77                 return obj;
  78         }
  79
  80         par_copy_object_no_checks ((char *)destination, vt, obj, objsize);
  81
  82         /* set the forwarding pointer */
  83         SGEN_FORWARD_OBJECT (obj, destination);
  84
  85         if (has_references) {
  86                 SGEN_LOG (9, "Enqueuing gray object %p (%s)", destination, sgen_client_vtable_get_name (vt));
  87                 GRAY_OBJECT_ENQUEUE_SERIAL (queue, (GCObject *)destination, sgen_vtable_get_descriptor (vt));
  88         }
  89
  90         return (GCObject *)destination;
  91 }
  92
  93 #if defined(COPY_OR_MARK_PARALLEL)
  94 static MONO_NEVER_INLINE GCObject *
  95 copy_object_no_checks_par (GCObject *obj, SgenGrayQueue *queue)
  96 {
  97         mword vtable_word = *(mword*)obj;
  98         GCObject *destination;
  99
 100         destination = (GCObject*) SGEN_VTABLE_IS_FORWARDED (vtable_word);
 101
 102         if (!destination) {
 103                 GCVTable vt = (GCVTable) vtable_word;
 104                 GCObject *final_destination;
 105                 /*
 106                  * At this point we know vt is not tagged and we shouldn't access the vtable through obj
 107                  * since it could get copied at any time by another thread.
 108                  */
 109                 gboolean has_references = SGEN_VTABLE_HAS_REFERENCES (vt);
 110                 mword objsize = SGEN_ALIGN_UP (sgen_client_par_object_get_size (vt, obj));
 111                 destination = COLLECTOR_PARALLEL_ALLOC_FOR_PROMOTION (vt, obj, objsize, has_references);
 112
 113                 par_copy_object_no_checks ((char*)destination, vt, obj, objsize);
 114
 115                 /* FIXME we might need a membar here so other threads see the vtable before we forward */
 116
 117                 /* set the forwarding pointer */
 118                 SGEN_FORWARD_OBJECT_PAR (obj, destination, final_destination);
 119
 120                 if (destination == final_destination) {
 121                         /* In a racing case, only the worker that allocated the object enqueues it */
 122                         if (has_references) {
 123                                 SGEN_LOG (9, "Enqueuing gray object %p (%s)", destination, sgen_client_vtable_get_name (vt));
 124                                 GRAY_OBJECT_ENQUEUE_PARALLEL (queue, (GCObject *)destination, sgen_vtable_get_descriptor (vt));
 125                         }
 126                 } else {
 127                         /*
 128                          * Unlikely case. Clear the allocated object so it doesn't confuse nursery
 129                          * card table scanning, since it can contain old invalid refs.
 130                          * FIXME make sure it is not a problem if another threads scans it while we clear
 131                          */
 132                         mono_gc_bzero_aligned (destination, objsize);
 133                         destination = final_destination;
 134                 }
 135         }
 136
 137         return destination;
 138 }
 139 #endif
 140
 141 #undef COLLECTOR_SERIAL_ALLOC_FOR_PROMOTION
 142 #undef COLLECTOR_PARALLEL_ALLOC_FOR_PROMOTION
 143 #undef collector_pin_object
 144 #undef COPY_OR_MARK_PARALLEL