From 33f0f68d590a460f84a0df0de10f29c4a582d7e7 Mon Sep 17 00:00:00 2001 From: Kenneth Graunke Date: Fri, 27 Mar 2015 19:24:33 -0700 Subject: [PATCH] ralloc: Implement a new ralloc_adopt() API. ralloc_adopt() reparents all children from one context to another. Conceptually, ralloc_adopt(new_ctx, old_ctx) behaves like this pseudocode: foreach child of old_ctx: ralloc_steal(new_ctx, child) However, ralloc provides no way to iterate over a memory context's children, and ralloc_adopt does this task more efficiently anyway. One potential use of this is to implement a memory-sweeper pass: first, steal all of a context's memory to a temporary context. Then, walk over anything that should be kept, and ralloc_steal it back to the original context. Finally, free the temporary context. This works when the context is something that can't be freed (i.e. an important structure). Signed-off-by: Kenneth Graunke Reviewed-by: Jason Ekstrand --- src/util/ralloc.c | 26 ++++++++++++++++++++++++++ src/util/ralloc.h | 7 +++++++ 2 files changed, 33 insertions(+) diff --git a/src/util/ralloc.c b/src/util/ralloc.c index 36bc61fd075..01719c888b1 100644 --- a/src/util/ralloc.c +++ b/src/util/ralloc.c @@ -271,6 +271,32 @@ ralloc_steal(const void *new_ctx, void *ptr) add_child(parent, info); } +void +ralloc_adopt(const void *new_ctx, void *old_ctx) +{ + ralloc_header *new_info, *old_info, *child; + + if (unlikely(old_ctx == NULL)) + return; + + old_info = get_header(old_ctx); + new_info = get_header(new_ctx); + + /* If there are no children, bail. */ + if (unlikely(old_info->child == NULL)) + return; + + /* Set all the children's parent to new_ctx; get a pointer to the last child. */ + for (child = old_info->child; child->next != NULL; child = child->next) { + child->parent = new_info; + } + + /* Connect the two lists together; parent them to new_ctx; make old_ctx empty. */ + child->next = new_info->child; + new_info->child = old_info->child; + old_info->child = NULL; +} + void * ralloc_parent(const void *ptr) { diff --git a/src/util/ralloc.h b/src/util/ralloc.h index f088a36274d..01f102ba244 100644 --- a/src/util/ralloc.h +++ b/src/util/ralloc.h @@ -234,6 +234,13 @@ void ralloc_free(void *ptr); */ void ralloc_steal(const void *new_ctx, void *ptr); +/** + * Reparent all children from one context to another. + * + * This effectively calls ralloc_steal(new_ctx, child) for all children of \p old_ctx. + */ +void ralloc_adopt(const void *new_ctx, void *old_ctx); + /** * Return the given pointer's ralloc context. */ -- 2.30.2