Add a magic number to debug_locks to better catch lock-coding errors.

Original description by Dave Hart:

 [This patch contains] the addition of a signature field to debug_lock
 initialized by the alloc routine and verified by the rest, to catch
 invalid lock pointers sooner. That helped me track down a nasty
 problem I had before adding the time.h include to
 libevent-internal.h, where different .c files had different ideas of
 whether event_base had a tod_tv_cache member depending on which
 included time.h before libevent-internal.h.

diff --git a/evthread.c b/evthread.c
index c96c6fd911572b9e044129b26c91728dfcfdd444..d9c54787a993611e6aabcf40f1f7b97cefc12303 100644 (file)
--- a/evthread.c
+++ b/evthread.c
@@ -109,7 +109,10 @@ evthread_set_condition_callbacks(const struct evthread_condition_callbacks *cbs)
        return 0;
 }
 
+#define DEBUG_LOCK_SIG 0xdeb0b10c
+
 struct debug_lock {
+       unsigned signature;
        unsigned locktype;
        unsigned long held_by;
        /* XXXX if we ever use read-write locks, we will need a separate
@@ -133,6 +136,7 @@ debug_lock_alloc(unsigned locktype)
        } else {
                result->lock = NULL;
        }
+       result->signature = DEBUG_LOCK_SIG;
        result->locktype = locktype;
        result->count = 0;
        result->held_by = 0;
@@ -145,6 +149,7 @@ debug_lock_free(void *lock_, unsigned locktype)
        struct debug_lock *lock = lock_;
        EVUTIL_ASSERT(lock->count == 0);
        EVUTIL_ASSERT(locktype == lock->locktype);
+       EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
        if (_original_lock_fns.free) {
                _original_lock_fns.free(lock->lock,
                    lock->locktype|EVTHREAD_LOCKTYPE_RECURSIVE);
@@ -157,6 +162,7 @@ debug_lock_free(void *lock_, unsigned locktype)
 static void
 evthread_debug_lock_mark_locked(unsigned mode, struct debug_lock *lock)
 {
+       EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
        ++lock->count;
        if (!(lock->locktype & EVTHREAD_LOCKTYPE_RECURSIVE))
                EVUTIL_ASSERT(lock->count == 1);
@@ -189,12 +195,15 @@ debug_lock_lock(unsigned mode, void *lock_)
 static void
 evthread_debug_lock_mark_unlocked(unsigned mode, struct debug_lock *lock)
 {
+       EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
        if (lock->locktype & EVTHREAD_LOCKTYPE_READWRITE)
                EVUTIL_ASSERT(mode & (EVTHREAD_READ|EVTHREAD_WRITE));
        else
                EVUTIL_ASSERT((mode & (EVTHREAD_READ|EVTHREAD_WRITE)) == 0);
        if (_evthread_id_fn) {
-               EVUTIL_ASSERT(lock->held_by == _evthread_id_fn());
+               unsigned long me;
+               me = _evthread_id_fn();
+               EVUTIL_ASSERT(lock->held_by == me);
                if (lock->count == 1)
                        lock->held_by = 0;
        }
@@ -218,6 +227,7 @@ debug_cond_wait(void *_cond, void *_lock, const struct timeval *tv)
 {
        int r;
        struct debug_lock *lock = _lock;
+       EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
        EVLOCK_ASSERT_LOCKED(_lock);
        evthread_debug_lock_mark_unlocked(0, lock);
        r = _original_cond_fns.wait_condition(_cond, lock->lock, tv);