mirror of
https://github.com/openvswitch/ovs
synced 2025-08-22 09:58:01 +00:00
Pass lock objects, not their addresses, to the annotation macros. Fixes: f21fa45f3085 ("lockfile: Minor code cleanup.") Tested-at: https://travis-ci.org/github/williamtu/ovs-travis/builds/666098338 Signed-off-by: William Tu <u9012063@gmail.com> Acked-by: Ben Pfaff <blp@ovn.org>
367 lines
10 KiB
C
367 lines
10 KiB
C
/* Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <config.h>
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#include "lockfile.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "coverage.h"
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#include "hash.h"
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#include "openvswitch/hmap.h"
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#include "ovs-thread.h"
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#include "timeval.h"
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#include "util.h"
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#include "openvswitch/vlog.h"
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VLOG_DEFINE_THIS_MODULE(lockfile);
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COVERAGE_DEFINE(lockfile_lock);
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COVERAGE_DEFINE(lockfile_error);
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COVERAGE_DEFINE(lockfile_unlock);
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struct lockfile {
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struct hmap_node hmap_node;
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char *name;
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dev_t device;
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ino_t inode;
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int fd;
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HANDLE lock_handle;
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};
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/* Lock table.
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*
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* We have to do this stupid dance because POSIX says that closing *any* file
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* descriptor for a file on which a process holds a lock drops *all* locks on
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* that file. That means that we can't afford to open a lockfile more than
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* once. */
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static struct ovs_mutex lock_table_mutex = OVS_MUTEX_INITIALIZER;
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static struct hmap lock_table__ = HMAP_INITIALIZER(&lock_table__);
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static struct hmap *const lock_table OVS_GUARDED_BY(lock_table_mutex)
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= &lock_table__;
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static void lockfile_unhash(struct lockfile *);
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static int lockfile_try_lock(const char *name, pid_t *pidp,
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struct lockfile **lockfilep)
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OVS_REQUIRES(lock_table_mutex);
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static void lockfile_do_unlock(struct lockfile * lockfile)
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OVS_REQUIRES(lock_table_mutex);
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/* Returns the name of the lockfile that would be created for locking a file
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* named 'filename_'. The caller is responsible for freeing the returned name,
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* with free(), when it is no longer needed. */
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char *
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lockfile_name(const char *filename_)
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{
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char *filename;
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const char *slash;
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char *lockname;
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/* If 'filename_' is a symlink, base the name of the lockfile on the
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* symlink's target rather than the name of the symlink. That way, if a
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* file is symlinked, but there is no symlink for its lockfile, then there
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* is only a single lockfile for both the source and the target of the
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* symlink, not one for each. */
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filename = follow_symlinks(filename_);
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slash = strrchr(filename, '/');
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#ifdef _WIN32
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char *backslash = strrchr(filename, '\\');
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if (backslash && (!slash || backslash > slash)) {
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slash = backslash;
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}
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#endif
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lockname = (slash
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? xasprintf("%.*s/.%s.~lock~",
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(int) (slash - filename), filename, slash + 1)
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: xasprintf(".%s.~lock~", filename));
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free(filename);
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return lockname;
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}
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/* Locks the configuration file against modification by other processes and
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* re-reads it from disk.
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*
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* Returns 0 on success, otherwise a positive errno value. On success,
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* '*lockfilep' is set to point to a new "struct lockfile *" that may be
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* unlocked with lockfile_unlock(). On failure, '*lockfilep' is set to
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* NULL. Will not block if the lock cannot be immediately acquired. */
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int
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lockfile_lock(const char *file, struct lockfile **lockfilep)
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{
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/* Only exclusive ("write") locks are supported. This is not a problem
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* because the Open vSwitch code that currently uses lock files does so in
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* stylized ways such that any number of readers may access a file while it
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* is being written. */
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char *lock_name;
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pid_t pid;
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int error;
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COVERAGE_INC(lockfile_lock);
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lock_name = lockfile_name(file);
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ovs_mutex_lock(&lock_table_mutex);
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error = lockfile_try_lock(lock_name, &pid, lockfilep);
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ovs_mutex_unlock(&lock_table_mutex);
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if (error) {
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COVERAGE_INC(lockfile_error);
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if (error == EACCES) {
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error = EAGAIN;
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}
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if (pid == getpid()) {
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VLOG_WARN("%s: cannot lock file because this process has already "
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"locked it", lock_name);
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} else if (pid) {
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VLOG_WARN("%s: cannot lock file because it is already locked by "
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"pid %ld", lock_name, (long int) pid);
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} else {
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VLOG_WARN("%s: failed to lock file: %s",
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lock_name, ovs_strerror(error));
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}
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}
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free(lock_name);
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return error;
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}
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/* Unlocks 'lockfile', which must have been created by a call to
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* lockfile_lock(), and frees 'lockfile'. */
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void
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lockfile_unlock(struct lockfile *lockfile)
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{
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if (lockfile) {
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ovs_mutex_lock(&lock_table_mutex);
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lockfile_do_unlock(lockfile);
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ovs_mutex_unlock(&lock_table_mutex);
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COVERAGE_INC(lockfile_unlock);
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free(lockfile->name);
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free(lockfile);
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}
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}
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/* Marks all the currently locked lockfiles as no longer locked. It makes
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* sense to call this function after fork(), because a child created by fork()
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* does not hold its parents' locks. */
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void
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lockfile_postfork(void)
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{
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struct lockfile *lockfile;
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ovs_mutex_lock(&lock_table_mutex);
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HMAP_FOR_EACH (lockfile, hmap_node, lock_table) {
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if (lockfile->fd >= 0) {
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VLOG_WARN("%s: child does not inherit lock", lockfile->name);
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lockfile_unhash(lockfile);
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}
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}
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ovs_mutex_unlock(&lock_table_mutex);
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}
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static uint32_t
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lockfile_hash(dev_t device, ino_t inode)
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{
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return hash_bytes(&device, sizeof device,
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hash_bytes(&inode, sizeof inode, 0));
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}
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static struct lockfile *
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lockfile_find(dev_t device, ino_t inode) OVS_REQUIRES(lock_table_mutex)
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{
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struct lockfile *lockfile;
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HMAP_FOR_EACH_WITH_HASH (lockfile, hmap_node,
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lockfile_hash(device, inode), lock_table) {
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if (lockfile->device == device && lockfile->inode == inode) {
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return lockfile;
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}
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}
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return NULL;
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}
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static void
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lockfile_unhash(struct lockfile *lockfile) OVS_REQUIRES(lock_table_mutex)
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{
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if (lockfile->fd >= 0) {
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close(lockfile->fd);
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lockfile->fd = -1;
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hmap_remove(lock_table, &lockfile->hmap_node);
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}
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}
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static struct lockfile *
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lockfile_register(const char *name, dev_t device, ino_t inode, int fd)
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OVS_REQUIRES(lock_table_mutex)
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{
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struct lockfile *lockfile;
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lockfile = lockfile_find(device, inode);
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if (lockfile) {
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VLOG_ERR("%s: lock file disappeared and reappeared!", name);
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lockfile_unhash(lockfile);
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}
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lockfile = xmalloc(sizeof *lockfile);
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lockfile->name = xstrdup(name);
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lockfile->device = device;
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lockfile->inode = inode;
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lockfile->fd = fd;
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hmap_insert(lock_table, &lockfile->hmap_node,
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lockfile_hash(device, inode));
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return lockfile;
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}
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#ifdef _WIN32
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static void
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lockfile_do_unlock(struct lockfile *lockfile)
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OVS_REQUIRES(lock_table_mutex)
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{
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if (lockfile->fd >= 0) {
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OVERLAPPED overl;
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overl.hEvent = 0;
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overl.Offset = 0;
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overl.OffsetHigh = 0;
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UnlockFileEx(lockfile->lock_handle, 0, 1, 0, &overl);
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close(lockfile->fd);
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lockfile->fd = -1;
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}
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}
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static int
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lockfile_try_lock(const char *name, pid_t *pidp, struct lockfile **lockfilep)
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OVS_REQUIRES(lock_table_mutex)
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{
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HANDLE lock_handle;
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BOOL retval;
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OVERLAPPED overl;
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struct lockfile *lockfile;
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int fd;
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*pidp = 0;
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fd = open(name, O_RDWR | O_CREAT, 0600);
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if (fd < 0) {
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VLOG_WARN("%s: failed to open lock file: %s",
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name, ovs_strerror(errno));
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return errno;
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}
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lock_handle = (HANDLE)_get_osfhandle(fd);
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if (lock_handle < 0) {
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VLOG_WARN("%s: failed to get the file handle: %s",
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name, ovs_strerror(errno));
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return errno;
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}
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/* Lock the file 'name' for the region that includes just the first
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* byte. */
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overl.hEvent = 0;
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overl.Offset = 0;
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overl.OffsetHigh = 0;
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retval = LockFileEx(lock_handle, LOCKFILE_EXCLUSIVE_LOCK
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| LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &overl);
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if (!retval) {
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VLOG_DBG("Failed to lock file : %s", ovs_lasterror_to_string());
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*pidp = getpid();
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return EDEADLK;
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}
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lockfile = xmalloc(sizeof *lockfile);
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lockfile->name = xstrdup(name);
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lockfile->fd = fd;
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lockfile->lock_handle = lock_handle;
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*lockfilep = lockfile;
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return 0;
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}
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#else /* !_WIN32 */
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static void
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lockfile_do_unlock(struct lockfile *lockfile)
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{
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lockfile_unhash(lockfile);
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}
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static int
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lockfile_try_lock(const char *name, pid_t *pidp, struct lockfile **lockfilep)
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OVS_REQUIRES(lock_table_mutex)
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{
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struct flock l;
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struct stat s;
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int error;
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int fd;
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*lockfilep = NULL;
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*pidp = 0;
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/* Check whether we've already got a lock on that file. */
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if (!stat(name, &s)) {
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if (lockfile_find(s.st_dev, s.st_ino)) {
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*pidp = getpid();
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return EDEADLK;
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}
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} else if (errno != ENOENT) {
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VLOG_WARN("%s: failed to stat lock file: %s",
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name, ovs_strerror(errno));
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return errno;
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}
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/* Open the lock file. */
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fd = open(name, O_RDWR | O_CREAT, 0600);
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if (fd < 0) {
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VLOG_WARN("%s: failed to open lock file: %s",
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name, ovs_strerror(errno));
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return errno;
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}
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/* Get the inode and device number for the lock table. */
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if (fstat(fd, &s)) {
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VLOG_ERR("%s: failed to fstat lock file: %s",
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name, ovs_strerror(errno));
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close(fd);
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return errno;
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}
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/* Try to lock the file. */
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memset(&l, 0, sizeof l);
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l.l_type = F_WRLCK;
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l.l_whence = SEEK_SET;
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l.l_start = 0;
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l.l_len = 0;
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error = fcntl(fd, F_SETLK, &l) == -1 ? errno : 0;
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if (!error) {
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*lockfilep = lockfile_register(name, s.st_dev, s.st_ino, fd);
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} else {
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if (!fcntl(fd, F_GETLK, &l) && l.l_type != F_UNLCK) {
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*pidp = l.l_pid;
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}
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close(fd);
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}
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return error;
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}
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#endif
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