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5e635e3960
The usual process flow is the main process opens and holds the lock to the index, does its thing, perhaps spawning children during the course, and then writes the resulting index out by releaseing the lock. However, the lockfile interface uses atexit(3) to clean it up, without regard to who actually created the lock. This typically leads to a confusing behaviour of lock being released too early when the child exits, and then the parent process when it calls commit_lockfile() finds that it cannot unlock it. This fixes the problem by recording who created and holds the lock, and upon atexit(3) handler, child simply ignores the lockfile the parent created. Signed-off-by: Junio C Hamano <junkio@cox.net>
100 lines
2.1 KiB
C
100 lines
2.1 KiB
C
/*
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* Copyright (c) 2005, Junio C Hamano
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*/
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#include "cache.h"
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static struct lock_file *lock_file_list;
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static const char *alternate_index_output;
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static void remove_lock_file(void)
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{
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pid_t me = getpid();
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while (lock_file_list) {
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if (lock_file_list->owner == me &&
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lock_file_list->filename[0])
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unlink(lock_file_list->filename);
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lock_file_list = lock_file_list->next;
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}
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}
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static void remove_lock_file_on_signal(int signo)
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{
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remove_lock_file();
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signal(SIGINT, SIG_DFL);
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raise(signo);
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}
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static int lock_file(struct lock_file *lk, const char *path)
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{
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int fd;
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sprintf(lk->filename, "%s.lock", path);
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fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
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if (0 <= fd) {
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lk->owner = getpid();
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if (!lk->on_list) {
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lk->next = lock_file_list;
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lock_file_list = lk;
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lk->on_list = 1;
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}
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if (lock_file_list) {
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signal(SIGINT, remove_lock_file_on_signal);
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atexit(remove_lock_file);
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}
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if (adjust_shared_perm(lk->filename))
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return error("cannot fix permission bits on %s",
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lk->filename);
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}
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else
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lk->filename[0] = 0;
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return fd;
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}
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int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on_error)
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{
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int fd = lock_file(lk, path);
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if (fd < 0 && die_on_error)
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die("unable to create '%s.lock': %s", path, strerror(errno));
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return fd;
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}
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int commit_lock_file(struct lock_file *lk)
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{
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char result_file[PATH_MAX];
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int i;
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strcpy(result_file, lk->filename);
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i = strlen(result_file) - 5; /* .lock */
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result_file[i] = 0;
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i = rename(lk->filename, result_file);
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lk->filename[0] = 0;
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return i;
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}
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int hold_locked_index(struct lock_file *lk, int die_on_error)
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{
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return hold_lock_file_for_update(lk, get_index_file(), die_on_error);
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}
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void set_alternate_index_output(const char *name)
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{
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alternate_index_output = name;
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}
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int commit_locked_index(struct lock_file *lk)
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{
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if (alternate_index_output) {
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int result = rename(lk->filename, alternate_index_output);
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lk->filename[0] = 0;
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return result;
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}
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else
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return commit_lock_file(lk);
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}
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void rollback_lock_file(struct lock_file *lk)
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{
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if (lk->filename[0])
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unlink(lk->filename);
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lk->filename[0] = 0;
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}
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