src/lxc/lxclock.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #ifndef __LXC_LXCLOCK_H
   4 #define __LXC_LXCLOCK_H
   5
   6 #include <fcntl.h>
   7 #include <semaphore.h>
   8 #include <string.h>
   9 #include <sys/file.h>
  10 #include <sys/stat.h>
  11 #include <time.h>
  12 #include <unistd.h>
  13
  14 #ifndef F_OFD_GETLK
  15 #define F_OFD_GETLK     36
  16 #endif
  17
  18 #ifndef F_OFD_SETLK
  19 #define F_OFD_SETLK     37
  20 #endif
  21
  22 #ifndef F_OFD_SETLKW
  23 #define F_OFD_SETLKW    38
  24 #endif
  25
  26 #define LXC_LOCK_ANON_SEM 1 /*!< Anonymous semaphore lock */
  27 #define LXC_LOCK_FLOCK    2 /*!< flock(2) lock */
  28
  29 /* private */
  30 /*!
  31  * LXC Lock
  32 */
  33 struct lxc_lock {
  34         short type; /*!< Lock type */
  35
  36         union {
  37                 sem_t *sem; /*!< Anonymous semaphore (LXC_LOCK_ANON_SEM) */
  38                 /*! LXC_LOCK_FLOCK details */
  39                 struct {
  40                         int   fd; /*!< fd on which a lock is held (if not -1) */
  41                         char *fname; /*!< Name of lock */
  42                 } f;
  43         } u; /*!< Container for lock type elements */
  44 };
  45
  46 /*!
  47  * \brief Create a new (unlocked) lock.
  48  *
  49  * \param lxcpath lxcpath lock should relate to.
  50  * \param name Name for lock.
  51  *
  52  * \return Newly-allocated lxclock on success, \c NULL on failure.
  53
  54  * \note If \p name is not given, create an unnamed semaphore
  55  *  (used to protect against racing threads).
  56  *
  57  * \note Note that an unnamed sem was malloced by us and needs to be freed.
  58  *
  59  * \internal \ref sem is initialized to a value of \c 1.
  60  * A 'sem_t *' which can be passed to \ref lxclock() and \ref lxcunlock()
  61  * will be placed in \c l->u.sem.
  62  *
  63  * If \ref lxcpath and \ref name are given (both must be given if either is
  64  * given) then a lockfile is created as \c /run/lxc/lock/$lxcpath/.$name if root,
  65  * or \c $XDG_RUNTIME_DIR/lxc/lock/$lxcpath/.$name if non-root.
  66  * The lock is used to protect the containers on-disk representation.
  67  *
  68  * \internal This function allocates the pathname for the given lock in memory
  69  * such that it can be can quickly opened and locked by \ref lxclock().
  70  * \c l->u.f.fname will contain the malloc'ed name (which must be
  71  * freed when the container is freed), and \c u.f.fd = -1.
  72  *
  73  */
  74 extern struct lxc_lock *lxc_newlock(const char *lxcpath, const char *name);
  75
  76 /*!
  77  * \brief Take an existing lock.
  78  *
  79  * \param lock Lock to operate on.
  80  * \param timeout Seconds to wait to take lock (\c 0 signifies an
  81  * indefinite wait).
  82  *
  83  * \return \c 0 if lock obtained, \c -2 on failure to set timeout,
  84  *  or \c -1 on any other error (\c errno will be set by \c sem_wait(3)
  85  * or \c fcntl(2)).
  86  *
  87  * \note \p timeout is (currently?) only supported for privlock, not
  88  * for slock.  Since currently there is not a single use of the timeout
  89  * (except in the test case) I may remove the support for it in sem as
  90  * well.
  91  */
  92 extern int lxclock(struct lxc_lock *lock, int timeout);
  93
  94 /*!
  95  * \brief Unlock specified lock previously locked using \ref lxclock().
  96  *
  97  * \param lock \ref lxc_lock.
  98  *
  99  * \return \c 0 on success, \c -2 if provided lock was not already held,
 100  * otherwise \c -1 with \c errno saved from \c fcntl(2) or sem_post function.
 101  */
 102 extern int lxcunlock(struct lxc_lock *lock);
 103
 104 /*!
 105  * \brief Free a lock created by \ref lxc_newlock().
 106  *
 107  * \param lock Lock.
 108  */
 109 extern void lxc_putlock(struct lxc_lock *lock);
 110
 111 /*!
 112  * \brief Lock the current process.
 113  */
 114 extern void process_lock(void);
 115
 116 /*!
 117  * \brief Unlock the current process.
 118  */
 119 extern void process_unlock(void);
 120
 121 struct lxc_container;
 122
 123 /*!
 124  * \brief Lock the containers memory.
 125  *
 126  * \param c Container.
 127  *
 128  * \return As for \ref lxclock().
 129  */
 130 extern int container_mem_lock(struct lxc_container *c);
 131
 132 /*!
 133  * \brief Unlock the containers memory.
 134  *
 135  * \param c Container.
 136  */
 137 extern void container_mem_unlock(struct lxc_container *c);
 138
 139 /*!
 140  * \brief Lock the containers disk data.
 141  *
 142  * \param c Container.
 143  *
 144  * \return \c 0 on success, or an \ref lxclock() error return
 145  * values on error.
 146  */
 147 extern int container_disk_lock(struct lxc_container *c);
 148
 149 /*!
 150  * \brief Unlock the containers disk data.
 151  *
 152  * \param c Container.
 153  *
 154  */
 155 extern void container_disk_unlock(struct lxc_container *c);
 156
 157 #endif