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eafa8a32bb
Define a new watcher type into list module. This type is similar to bref and can be used to register an element which is currently tracking a dynamic target. Contrary to bref, if the target is freed, every watcher element are updated to point to a next valid entry or NULL. This type will simplify handling of dynamic servers deletion, in particular while stats dump are performed. This patch is not a bug-fix. However, it is mandatory to fix a race condition in dynamic servers. Thus, it should be backported along the next commit up to 2.6.
85 lines
3.0 KiB
C
85 lines
3.0 KiB
C
/*
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* include/haproxy/list-t.h
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* Circular list manipulation types definitions
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*
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* Copyright (C) 2002-2020 Willy Tarreau - w@1wt.eu
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation, version 2.1
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* exclusively.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _HAPROXY_LIST_T_H
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#define _HAPROXY_LIST_T_H
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/* these are circular or bidirectionnal lists only. Each list pointer points to
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* another list pointer in a structure, and not the structure itself. The
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* pointer to the next element MUST be the first one so that the list is easily
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* cast as a single linked list or pointer.
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*/
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struct list {
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struct list *n; /* next */
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struct list *p; /* prev */
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};
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/* This is similar to struct list, but we want to be sure the compiler will
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* yell at you if you use macroes for one when you're using the other. You have
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* to expicitely cast if that's really what you want to do.
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*/
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struct mt_list {
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struct mt_list *next;
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struct mt_list *prev;
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};
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/* a back-ref is a pointer to a target list entry. It is used to detect when an
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* element being deleted is currently being tracked by another user. The best
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* example is a user dumping the session table. The table does not fit in the
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* output buffer so we have to set a mark on a session and go on later. But if
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* that marked session gets deleted, we don't want the user's pointer to go in
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* the wild. So we can simply link this user's request to the list of this
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* session's users, and put a pointer to the list element in ref, that will be
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* used as the mark for next iteration.
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*/
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struct bref {
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struct list users;
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struct list *ref; /* pointer to the target's list entry */
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};
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/* Similar to bref. Used to reference an element which is tracking a dynamic
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* target. The main advantage over bref is that when target is freed, each
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* elements pointers are automatically updated to the next entry or NULL if
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* target was the last one.
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*/
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struct watcher {
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struct mt_list el; /* attach point into target list */
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void **pptr; /* pointer to element which points to target */
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size_t off; /* offset into target type for mtlist storage of watcher */
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};
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/* a word list is a generic list with a pointer to a string in each element. */
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struct wordlist {
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struct list list;
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char *s;
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};
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/* this is the same as above with an additional pointer to a condition. */
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struct cond_wordlist {
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struct list list;
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void *cond;
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char *s;
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};
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#endif /* _HAPROXY_LIST_T_H */
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