Fix tracing_mutex_assert() by tracking the thread ID of the lock owner and

behave properly when the mutex is held by another thread.


git-svn-id: svn://svn.code.sf.net/p/libkqueue/code/trunk@514 fb4e3144-bc1c-4b72-a658-5bcd248dd7f7

src/common/debug.h

@@ -92,26 +92,35 @@ extern char *KQUEUE_DEBUG_IDENT;
 typedef struct {
     pthread_mutex_t mtx_lock; 
     int mtx_status; 
+    int mtx_owner;
 } tracing_mutex_t; 
 
 # define tracing_mutex_init(mtx, attr) do { \
     pthread_mutex_init(&(mtx)->mtx_lock, (attr)); \
     (mtx)->mtx_status = MTX_UNLOCKED; \
+    (mtx)->mtx_owner = -1; \
 } while (0)
 
 # define tracing_mutex_destroy(mtx) pthread_mutex_destroy(&(mtx)->mtx_lock)
 
-# define tracing_mutex_assert(x,y)   assert((x)->mtx_status == (y))
+# define tracing_mutex_assert(x,y) do { \
+  if ((y) == MTX_UNLOCKED) \
+      assert((x)->mtx_status == MTX_UNLOCKED || (x)->mtx_owner != THREAD_ID); \
+  else if ((y) == MTX_LOCKED) \
+      assert((x)->mtx_status == MTX_LOCKED); \
+} while (0)
 
 # define tracing_mutex_lock(x)  do { \
     dbg_printf("waiting for %s", #x); \
     pthread_mutex_lock(&((x)->mtx_lock)); \
     dbg_printf("locked %s", #x); \
+    (x)->mtx_owner = THREAD_ID; \
     (x)->mtx_status = MTX_LOCKED; \
 } while (0)
 
 # define tracing_mutex_unlock(x)  do { \
     (x)->mtx_status = MTX_UNLOCKED; \
+    (x)->mtx_owner = -1; \
     pthread_mutex_unlock(&((x)->mtx_lock)); \
     dbg_printf("unlocked %s", # x); \
 } while (0)

test/lockstat.c

@@ -14,6 +14,8 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <err.h>
+#include <pthread.h>
 #include "../src/common/private.h"
 
 int DEBUG_KQUEUE = 1;
@@ -23,11 +25,20 @@ struct foo {
     tracing_mutex_t foo_lock;
 };
 
+void *test_assertion(void *_x)
+{
+    struct foo *x = (struct foo *) _x;
+   tracing_mutex_assert(&x->foo_lock, MTX_UNLOCKED);
+   pthread_exit(NULL);
+}
+
 /*
  * Test the lockstat.h API
  */
 int main() {
     struct foo x;
+    pthread_t tid;
+    void *rv;
     
     tracing_mutex_init(&x.foo_lock, NULL);
     tracing_mutex_lock(&x.foo_lock);
@@ -35,6 +46,16 @@ int main() {
     tracing_mutex_unlock(&x.foo_lock);
     tracing_mutex_assert(&x.foo_lock, MTX_UNLOCKED);
 
+    /*
+     * Ensure that the assert() function works when there
+     * are multiple threads contenting for the mutex.
+     */
+    tracing_mutex_lock(&x.foo_lock);
+    if (pthread_create(&tid, NULL, test_assertion, &x) != 0)
+        err(1, "pthread_create");
+    pthread_join(tid, &rv);
+    tracing_mutex_unlock(&x.foo_lock);
+
     puts("+OK");
     return (0);
 }