author | Lars Hjemli <hjemli@gmail.com> | 2006-12-11 21:53:50 (UTC) |
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committer | Lars Hjemli <hjemli@gmail.com> | 2006-12-11 21:53:50 (UTC) |
commit | fbaf1171b4e343929dd43ecac7cd9d1c692b84ec (patch) (side-by-side diff) | |
tree | 40b7007b2e1e85f2e91e052b33555df2e9fb5e14 | |
parent | 44923f8953c66dc9b852316b655ab3b5aec9478e (diff) | |
download | cgit-fbaf1171b4e343929dd43ecac7cd9d1c692b84ec.zip cgit-fbaf1171b4e343929dd43ecac7cd9d1c692b84ec.tar.gz cgit-fbaf1171b4e343929dd43ecac7cd9d1c692b84ec.tar.bz2 |
Don't truncate valid cachefiles
An embarrassing thinko in cgit_check_cache() would truncate valid cachefiles
in the following situation:
1) process A notices a missing/expired cachefile
2) process B gets scheduled, locks, fills and unlocks the cachefile
3) process A gets scheduled, locks the cachefile, notices that the cachefile
now exist/is not expired anymore, and continues to overwrite it with an
empty lockfile.
Thanks to Linus for noticing (again).
Signed-off-by: Lars Hjemli <hjemli@gmail.com>
-rw-r--r-- | cache.c | 5 | ||||
-rw-r--r-- | cgit.c | 10 | ||||
-rw-r--r-- | cgit.h | 1 |
3 files changed, 14 insertions, 2 deletions
@@ -86,22 +86,27 @@ int cache_lock(struct cacheitem *item) if (item->fd == NOLOCK && errno == ENOENT && cache_create_dirs()) goto top; if (item->fd == NOLOCK && errno == EEXIST && cache_refill_overdue(lockfile) && !unlink(lockfile)) goto top; return (item->fd > 0); } int cache_unlock(struct cacheitem *item) { close(item->fd); return (rename(fmt("%s.lock", item->name), item->name) == 0); } +int cache_cancel_lock(struct cacheitem *item) +{ + return (unlink(fmt("%s.lock", item->name)) == 0); +} + int cache_expired(struct cacheitem *item) { if (item->ttl < 0) return 0; return item->st.st_mtime + item->ttl * 60 < time(NULL); } @@ -48,39 +48,45 @@ static void cgit_fill_cache(struct cacheitem *item) static void cgit_check_cache(struct cacheitem *item) { int i = 0; cache_prepare(item); top: if (++i > cgit_max_lock_attempts) { die("cgit_refresh_cache: unable to lock %s: %s", item->name, strerror(errno)); } if (!cache_exist(item)) { if (!cache_lock(item)) { sleep(1); goto top; } - if (!cache_exist(item)) + if (!cache_exist(item)) { cgit_fill_cache(item); cache_unlock(item); + } else { + cache_cancel_lock(item); + } } else if (cache_expired(item) && cache_lock(item)) { - if (cache_expired(item)) + if (cache_expired(item)) { cgit_fill_cache(item); cache_unlock(item); + } else { + cache_cancel_lock(item); + } } } static void cgit_print_cache(struct cacheitem *item) { static char buf[4096]; ssize_t i; int fd = open(item->name, O_RDONLY); if (fd<0) die("Unable to open cached file %s", item->name); while((i=read(fd, buf, sizeof(buf))) > 0) write(STDOUT_FILENO, buf, i); close(fd); @@ -53,32 +53,33 @@ extern void cgit_querystring_cb(const char *name, const char *value); extern char *fmt(const char *format,...); extern void html(const char *txt); extern void htmlf(const char *format,...); extern void html_txt(char *txt); extern void html_attr(char *txt); extern void html_link_open(char *url, char *title, char *class); extern void html_link_close(void); extern int cgit_read_config(const char *filename, configfn fn); extern int cgit_parse_query(char *txt, configfn fn); extern void cache_prepare(struct cacheitem *item); extern int cache_lock(struct cacheitem *item); extern int cache_unlock(struct cacheitem *item); +extern int cache_cancel_lock(struct cacheitem *item); extern int cache_exist(struct cacheitem *item); extern int cache_expired(struct cacheitem *item); extern char *cgit_repourl(const char *reponame); extern char *cgit_pageurl(const char *reponame, const char *pagename, const char *query); extern void cgit_print_error(char *msg); extern void cgit_print_docstart(char *title, struct cacheitem *item); extern void cgit_print_docend(); extern void cgit_print_pageheader(char *title); extern void cgit_print_repolist(struct cacheitem *item); extern void cgit_print_summary(); extern void cgit_print_log(const char *tip, int ofs, int cnt); extern void cgit_print_view(char *hex); |