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Avoid infinite loops in caching layer

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Add a global variable, cgit_max_lock_attemps, to avoid the possibility of
infinite loops when failing to acquire a lockfile. This could happen on
broken setups or under crazy server load.

Incidentally, this also fixes a lurking bug in cache_lock() where an
uninitialized returnvalue was used.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
This commit is contained in:
Lars Hjemli 2006-12-11 12:10:12 +01:00
parent a581ed8d6c
commit 318d106300
3 changed files with 31 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
cache.c
View File

@ -61,26 +61,35 @@ int cache_create_dirs()
return 1;
}
int cache_refill_overdue(const char *lockfile)
{
struct stat st;
if (stat(lockfile, &st))
return 0;
else
return (time(NULL) - st.st_mtime > cgit_cache_max_create_time);
}
int cache_lock(struct cacheitem *item)
{
int ret;
int i = 0;
char *lockfile = fmt("%s.lock", item->name);
top:
item->fd = open(lockfile, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR|S_IWUSR);
if (++i > cgit_max_lock_attempts)
die("cache_lock: unable to lock %s: %s",
item->name, strerror(errno));
item->fd = open(lockfile, O_WRONLY|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR);
if (item->fd == NOLOCK && errno == ENOENT && cache_create_dirs())
goto top;
if (item->fd == NOLOCK && errno == EEXIST) {
struct stat st;
time_t t;
if (stat(lockfile, &st))
return ret;
t = time(NULL);
if (t-st.st_mtime > cgit_cache_max_create_time &&
!unlink(lockfile))
if (item->fd == NOLOCK && errno == EEXIST &&
cache_refill_overdue(lockfile) && !unlink(lockfile))
goto top;
return 0;
}
return (item->fd > 0);
}

9
cgit.c
View File

@ -31,6 +31,7 @@ char *cgit_virtual_root = NULL;
char *cgit_cache_root = "/var/cache/cgit";
int cgit_max_lock_attempts = 5;
int cgit_cache_root_ttl = 5;
int cgit_cache_repo_ttl = 5;
int cgit_cache_dynamic_ttl = 5;
@ -465,11 +466,17 @@ static void cgit_fill_cache(struct cacheitem *item)
static void cgit_refresh_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)) {
sched_yield();
sleep(1);
goto top;
}
if (!cache_exist(item))

1
cgit.h
View File

@ -23,6 +23,7 @@ extern char *cgit_logo_link;
extern char *cgit_virtual_root;
extern char *cgit_cache_root;
extern int cgit_max_lock_attempts;
extern int cgit_cache_root_ttl;
extern int cgit_cache_repo_ttl;
extern int cgit_cache_dynamic_ttl;