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5 * Copyright © 2012 Serge Hallyn <serge.hallyn@ubuntu.com>.
6 * Copyright © 2012 Canonical Ltd.
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 #ifndef __LXC_LXCLOCK_H
24 #define __LXC_LXCLOCK_H
27 #include <semaphore.h>
35 #define F_OFD_GETLK 36
39 #define F_OFD_SETLK 37
43 #define F_OFD_SETLKW 38
46 #define LXC_LOCK_ANON_SEM 1 /*!< Anonymous semaphore lock */
47 #define LXC_LOCK_FLOCK 2 /*!< flock(2) lock */
54 short type
; /*!< Lock type */
57 sem_t
*sem
; /*!< Anonymous semaphore (LXC_LOCK_ANON_SEM) */
58 /*! LXC_LOCK_FLOCK details */
60 int fd
; /*!< fd on which a lock is held (if not -1) */
61 char *fname
; /*!< Name of lock */
63 } u
; /*!< Container for lock type elements */
67 * \brief Create a new (unlocked) lock.
69 * \param lxcpath lxcpath lock should relate to.
70 * \param name Name for lock.
72 * \return Newly-allocated lxclock on success, \c NULL on failure.
74 * \note If \p name is not given, create an unnamed semaphore
75 * (used to protect against racing threads).
77 * \note Note that an unnamed sem was malloced by us and needs to be freed.
79 * \internal \ref sem is initialized to a value of \c 1.
80 * A 'sem_t *' which can be passed to \ref lxclock() and \ref lxcunlock()
81 * will be placed in \c l->u.sem.
83 * If \ref lxcpath and \ref name are given (both must be given if either is
84 * given) then a lockfile is created as \c /run/lxc/lock/$lxcpath/.$name if root,
85 * or \c $XDG_RUNTIME_DIR/lxc/lock/$lxcpath/.$name if non-root.
86 * The lock is used to protect the containers on-disk representation.
88 * \internal This function allocates the pathname for the given lock in memory
89 * such that it can be can quickly opened and locked by \ref lxclock().
90 * \c l->u.f.fname will contain the malloc'ed name (which must be
91 * freed when the container is freed), and \c u.f.fd = -1.
94 extern struct lxc_lock
*lxc_newlock(const char *lxcpath
, const char *name
);
97 * \brief Take an existing lock.
99 * \param lock Lock to operate on.
100 * \param timeout Seconds to wait to take lock (\c 0 signifies an
103 * \return \c 0 if lock obtained, \c -2 on failure to set timeout,
104 * or \c -1 on any other error (\c errno will be set by \c sem_wait(3)
107 * \note \p timeout is (currently?) only supported for privlock, not
108 * for slock. Since currently there is not a single use of the timeout
109 * (except in the test case) I may remove the support for it in sem as
112 extern int lxclock(struct lxc_lock
*lock
, int timeout
);
115 * \brief Unlock specified lock previously locked using \ref lxclock().
117 * \param lock \ref lxc_lock.
119 * \return \c 0 on success, \c -2 if provided lock was not already held,
120 * otherwise \c -1 with \c errno saved from \c fcntl(2) or sem_post function.
122 extern int lxcunlock(struct lxc_lock
*lock
);
125 * \brief Free a lock created by \ref lxc_newlock().
129 extern void lxc_putlock(struct lxc_lock
*lock
);
132 * \brief Lock the current process.
134 extern void process_lock(void);
137 * \brief Unlock the current process.
139 extern void process_unlock(void);
141 struct lxc_container
;
144 * \brief Lock the containers memory.
146 * \param c Container.
148 * \return As for \ref lxclock().
150 extern int container_mem_lock(struct lxc_container
*c
);
153 * \brief Unlock the containers memory.
155 * \param c Container.
157 extern void container_mem_unlock(struct lxc_container
*c
);
160 * \brief Lock the containers disk data.
162 * \param c Container.
164 * \return \c 0 on success, or an \ref lxclock() error return
167 extern int container_disk_lock(struct lxc_container
*c
);
170 * \brief Unlock the containers disk data.
172 * \param c Container.
175 extern void container_disk_unlock(struct lxc_container
*c
);