[PATCH 3/6] tools/libxs: Rationalise the definition of struct xs_handle

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Right now there are two completely different struct xs_handle definitions,
depend on #ifdef USE_PTHREAD.  One is especially well hidden, and often
escapes updates.

Rework struct xs_handle using some interior ifdefary.  It's slightly longer,
but much easier to follow.  Importanly, this makes it much harder to forget
the !PTHREAD case when adding a "common" variable.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Anthony PERARD <anthony.perard@xxxxxxxxxx>
CC: Juergen Gross <jgross@xxxxxxxx>
---
 tools/libs/store/xs.c | 77 +++++++++++++++++++++----------------------
 1 file changed, 37 insertions(+), 40 deletions(-)

diff --git a/tools/libs/store/xs.c b/tools/libs/store/xs.c
index 1b5a913a1594..96ea2b192924 100644
--- a/tools/libs/store/xs.c
+++ b/tools/libs/store/xs.c
@@ -40,6 +40,14 @@
 #include <xentoolcore_internal.h>
 #include <xen_list.h>
 
+#ifdef USE_PTHREAD
+# include <pthread.h>
+#endif
+
+#ifdef USE_DLSYM
+# include <dlfcn.h>
+#endif
+
 #ifndef O_CLOEXEC
 #define O_CLOEXEC 0
 #endif
@@ -54,14 +62,6 @@ struct xs_stored_msg {
        char *body;
 };
 
-#ifdef USE_PTHREAD
-
-#include <pthread.h>
-
-#ifdef USE_DLSYM
-#include <dlfcn.h>
-#endif
-
 struct xs_handle {
        /* Communications channel to xenstore daemon. */
        int fd;
@@ -71,16 +71,20 @@ struct xs_handle {
          * A read thread which pulls messages off the comms channel and
          * signals waiters.
          */
+#ifdef USE_PTHREAD
        pthread_t read_thr;
        int read_thr_exists;
+#endif
 
        /*
          * A list of fired watch messages, protected by a mutex. Users can
          * wait on the conditional variable until a watch is pending.
          */
        XEN_TAILQ_HEAD(, struct xs_stored_msg) watch_list;
+#ifdef USE_PTHREAD
        pthread_mutex_t watch_mutex;
        pthread_cond_t watch_condvar;
+#endif
 
        /* Clients can select() on this pipe to wait for a watch to fire. */
        int watch_pipe[2];
@@ -93,6 +97,7 @@ struct xs_handle {
          * conditional variable for its response.
          */
        XEN_TAILQ_HEAD(, struct xs_stored_msg) reply_list;
+#ifdef USE_PTHREAD
        pthread_mutex_t reply_mutex;
        pthread_cond_t reply_condvar;
 
@@ -112,55 +117,47 @@ struct xs_handle {
         *     reply_mutex
         *     watch_mutex
         */
+#endif
 };
 
-#define mutex_lock(m)          pthread_mutex_lock(m)
-#define mutex_unlock(m)                pthread_mutex_unlock(m)
-#define condvar_signal(c)      pthread_cond_signal(c)
-#define condvar_wait(c,m)      pthread_cond_wait(c,m)
-#define cleanup_push(f, a)     \
-    pthread_cleanup_push((void (*)(void *))(f), (void *)(a))
+
+#ifdef USE_PTHREAD
+
+# define mutex_lock(m)             pthread_mutex_lock(m)
+# define mutex_unlock(m)           pthread_mutex_unlock(m)
+# define condvar_signal(c)         pthread_cond_signal(c)
+# define condvar_wait(c, m)        pthread_cond_wait(c, m)
+# define cleanup_push(f, a)        pthread_cleanup_push((void (*)(void *))(f), 
(void *)(a))
 /*
  * Some definitions of pthread_cleanup_pop() are a macro starting with an
  * end-brace. GCC then complains if we immediately precede that with a label.
  * Hence we insert a dummy statement to appease the compiler in this situation.
  */
-#define cleanup_pop(run)        ((void)0); pthread_cleanup_pop(run)
+# define cleanup_pop(run)          ((void)0); pthread_cleanup_pop(run)
 
-#define read_thread_exists(h)  (h->read_thr_exists)
+# define read_thread_exists(h)     ((h)->read_thr_exists)
 
 /* Because pthread_cleanup_p* are not available when USE_PTHREAD is
  * disabled, use these macros which convert appropriately. */
-#define cleanup_push_heap(p)        cleanup_push(free, p)
-#define cleanup_pop_heap(run, p)    cleanup_pop((run))
+# define cleanup_push_heap(p)      cleanup_push(free, p)
+# define cleanup_pop_heap(run, p)  cleanup_pop((run))
 
 static void *read_thread(void *arg);
 
-#else /* !defined(USE_PTHREAD) */
+#else /* USE_PTHREAD */
 
-struct xs_handle {
-       int fd;
-       Xentoolcore__Active_Handle tc_ah; /* for restrict */
-       XEN_TAILQ_HEAD(, struct xs_stored_msg) reply_list;
-       XEN_TAILQ_HEAD(, struct xs_stored_msg) watch_list;
-       /* Clients can select() on this pipe to wait for a watch to fire. */
-       int watch_pipe[2];
-       /* Filtering watch event in unwatch function? */
-       bool unwatch_filter;
-};
+# define mutex_lock(m)               ((void)0)
+# define mutex_unlock(m)             ((void)0)
+# define condvar_signal(c)           ((void)0)
+# define condvar_wait(c, m)          ((void)0)
+# define cleanup_push(f, a)          ((void)0)
+# define cleanup_pop(run)            ((void)0)
+# define read_thread_exists(h)       (0)
+# define cleanup_push_heap(p)        ((void)0)
+# define cleanup_pop_heap(run, p)    do { if ((run)) free(p); } while(0)
 
-#define mutex_lock(m)          ((void)0)
-#define mutex_unlock(m)                ((void)0)
-#define condvar_signal(c)      ((void)0)
-#define condvar_wait(c,m)      ((void)0)
-#define cleanup_push(f, a)     ((void)0)
-#define cleanup_pop(run)       ((void)0)
-#define read_thread_exists(h)  (0)
+#endif /* !USE_PTHREAD */
 
-#define cleanup_push_heap(p)        ((void)0)
-#define cleanup_pop_heap(run, p)    do { if ((run)) free(p); } while(0)
-
-#endif
 
 static int read_message(struct xs_handle *h, int nonblocking);
 
-- 
2.39.2