Re: [Qemu-devel] [PATCH] trace: add glib 2.32+ static GMutex support

2013-12-13 Thread Stefan Hajnoczi 
On Thu, Dec 12, 2013 at 07:36:18PM +0400, Michael Tokarev wrote:
 12.12.2013 18:52, Stefan Hajnoczi wrote:
  The GStaticMutex API was deprecated in glib 2.32.  We cannot switch over
  to GMutex unconditionally since we would drop support for older glib
  versions.  But the deprecated API warnings during build are annoying so
  use static GMutex when possible.
  
  Signed-off-by: Stefan Hajnoczi stefa...@redhat.com
  ---
   trace/simple.c | 45 ++---
   1 file changed, 38 insertions(+), 7 deletions(-)
  
  diff --git a/trace/simple.c b/trace/simple.c
  index 1e3f691..941f7ea 100644
  --- a/trace/simple.c
  +++ b/trace/simple.c
  @@ -39,7 +39,11 @@
* Trace records are written out by a dedicated thread.  The thread waits 
  for
* records to become available, writes them out, and then waits again.
*/
  +#if GLIB_CHECK_VERSION(2, 32, 0)
  +static GMutex trace_lock;
  +#else
   static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
  +#endif
   
   /* g_cond_new() was deprecated in glib 2.31 but we still need to support 
  it */
   #if GLIB_CHECK_VERSION(2, 31, 0)
  @@ -86,6 +90,34 @@ typedef struct {
   static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
   static unsigned int write_to_buffer(unsigned int idx, void *dataptr, 
  size_t size);
   
  +/* Hide changes in glib mutex APIs */
  +static void lock_trace_lock(void)
  +{
  +#if GLIB_CHECK_VERSION(2, 32, 0)
  +g_mutex_lock(trace_lock);
  +#else
  +g_static_mutex_lock(trace_lock);
  +#endif
  +}
  +
  +static void unlock_trace_lock(void)
  +{
  +#if GLIB_CHECK_VERSION(2, 32, 0)
  +g_mutex_unlock(trace_lock);
  +#else
  +g_static_mutex_unlock(trace_lock);
  +#endif
  +}
  +
  +static GMutex *get_trace_lock_mutex(void)
  +{
  +#if GLIB_CHECK_VERSION(2, 32, 0)
  +return trace_lock;
  +#else
  +return g_static_mutex_get_mutex(trace_lock);
  +#endif
  +}
 
 
 I'd group mutex definition above with all the functions accessing it,
 and also make the functions inline.
 
 Well, to my taste, this is a good example where #define is better than
 an inline function.  Compare the above with:
 
 diff --git a/trace/simple.c b/trace/simple.c
 index 1e3f691..2e55ac1 100644
 --- a/trace/simple.c
 +++ b/trace/simple.c
 @@ -39,7 +39,17 @@
   * Trace records are written out by a dedicated thread.  The thread waits for
   * records to become available, writes them out, and then waits again.
   */
 +#if GLIB_CHECK_VERSION(2, 32, 0)
 +static GMutex trace_lock;
 +#define lock_trace_lock() g_mutex_lock(trace_lock)
 +#define unlock_trace_lock() g_mutex_unlock(trace_lock)
 +#define get_trace_lock_mutex() (trace_lock)
 +#else
  static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
 +#define lock_trace_lock() g_static_mutex_lock(trace_lock)
 +#define unlock_trace_lock() g_static_mutex_unlock(trace_lock)
 +#define get_trace_lock_mutex() g_static_mutex_get_mutex(trace_lock)
 +#endif
 
  /* g_cond_new() was deprecated in glib 2.31 but we still need to support it 
 */
  #if GLIB_CHECK_VERSION(2, 31, 0)
 
 (#defines here and elsewhere has added bonus - when debugging, debugger
 does not step into the inline functions, -- such stepping is quite annoying).
 
 But somehow many developers prefer inline functions (sometimes it is better
 indeed, especially in a commonly used header files, and when the functions
 has complex or many parameters; in this case we have much simpler situation.
 
 For fun, this #ifdeffery is 5 times larger than the actual users of the
 functions being defined :)

Yes, I think you are right.  In general I avoid using macros but here it
does make things nicer.

Stefan

[Qemu-devel] [PATCH] trace: add glib 2.32+ static GMutex support

2013-12-12 Thread Stefan Hajnoczi 
The GStaticMutex API was deprecated in glib 2.32.  We cannot switch over
to GMutex unconditionally since we would drop support for older glib
versions.  But the deprecated API warnings during build are annoying so
use static GMutex when possible.

Signed-off-by: Stefan Hajnoczi stefa...@redhat.com
---
 trace/simple.c | 45 ++---
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/trace/simple.c b/trace/simple.c
index 1e3f691..941f7ea 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -39,7 +39,11 @@
  * Trace records are written out by a dedicated thread.  The thread waits for
  * records to become available, writes them out, and then waits again.
  */
+#if GLIB_CHECK_VERSION(2, 32, 0)
+static GMutex trace_lock;
+#else
 static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
+#endif
 
 /* g_cond_new() was deprecated in glib 2.31 but we still need to support it */
 #if GLIB_CHECK_VERSION(2, 31, 0)
@@ -86,6 +90,34 @@ typedef struct {
 static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
 static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t 
size);
 
+/* Hide changes in glib mutex APIs */
+static void lock_trace_lock(void)
+{
+#if GLIB_CHECK_VERSION(2, 32, 0)
+g_mutex_lock(trace_lock);
+#else
+g_static_mutex_lock(trace_lock);
+#endif
+}
+
+static void unlock_trace_lock(void)
+{
+#if GLIB_CHECK_VERSION(2, 32, 0)
+g_mutex_unlock(trace_lock);
+#else
+g_static_mutex_unlock(trace_lock);
+#endif
+}
+
+static GMutex *get_trace_lock_mutex(void)
+{
+#if GLIB_CHECK_VERSION(2, 32, 0)
+return trace_lock;
+#else
+return g_static_mutex_get_mutex(trace_lock);
+#endif
+}
+
 static void clear_buffer_range(unsigned int idx, size_t len)
 {
 uint32_t num = 0;
@@ -139,27 +171,26 @@ static bool get_trace_record(unsigned int idx, 
TraceRecord **recordptr)
  */
 static void flush_trace_file(bool wait)
 {
-g_static_mutex_lock(trace_lock);
+lock_trace_lock();
 trace_available = true;
 g_cond_signal(trace_available_cond);
 
 if (wait) {
-g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(trace_lock));
+g_cond_wait(trace_empty_cond, get_trace_lock_mutex());
 }
 
-g_static_mutex_unlock(trace_lock);
+unlock_trace_lock();
 }
 
 static void wait_for_trace_records_available(void)
 {
-g_static_mutex_lock(trace_lock);
+lock_trace_lock();
 while (!(trace_available  trace_writeout_enabled)) {
 g_cond_signal(trace_empty_cond);
-g_cond_wait(trace_available_cond,
-g_static_mutex_get_mutex(trace_lock));
+g_cond_wait(trace_available_cond, get_trace_lock_mutex());
 }
 trace_available = false;
-g_static_mutex_unlock(trace_lock);
+unlock_trace_lock();
 }
 
 static gpointer writeout_thread(gpointer opaque)
-- 
1.8.4.2

Re: [Qemu-devel] [PATCH] trace: add glib 2.32+ static GMutex support

2013-12-12 Thread Michael Tokarev 
12.12.2013 18:52, Stefan Hajnoczi wrote:
 The GStaticMutex API was deprecated in glib 2.32.  We cannot switch over
 to GMutex unconditionally since we would drop support for older glib
 versions.  But the deprecated API warnings during build are annoying so
 use static GMutex when possible.
 
 Signed-off-by: Stefan Hajnoczi stefa...@redhat.com
 ---
  trace/simple.c | 45 ++---
  1 file changed, 38 insertions(+), 7 deletions(-)
 
 diff --git a/trace/simple.c b/trace/simple.c
 index 1e3f691..941f7ea 100644
 --- a/trace/simple.c
 +++ b/trace/simple.c
 @@ -39,7 +39,11 @@
   * Trace records are written out by a dedicated thread.  The thread waits for
   * records to become available, writes them out, and then waits again.
   */
 +#if GLIB_CHECK_VERSION(2, 32, 0)
 +static GMutex trace_lock;
 +#else
  static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
 +#endif
  
  /* g_cond_new() was deprecated in glib 2.31 but we still need to support it 
 */
  #if GLIB_CHECK_VERSION(2, 31, 0)
 @@ -86,6 +90,34 @@ typedef struct {
  static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
  static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t 
 size);
  
 +/* Hide changes in glib mutex APIs */
 +static void lock_trace_lock(void)
 +{
 +#if GLIB_CHECK_VERSION(2, 32, 0)
 +g_mutex_lock(trace_lock);
 +#else
 +g_static_mutex_lock(trace_lock);
 +#endif
 +}
 +
 +static void unlock_trace_lock(void)
 +{
 +#if GLIB_CHECK_VERSION(2, 32, 0)
 +g_mutex_unlock(trace_lock);
 +#else
 +g_static_mutex_unlock(trace_lock);
 +#endif
 +}
 +
 +static GMutex *get_trace_lock_mutex(void)
 +{
 +#if GLIB_CHECK_VERSION(2, 32, 0)
 +return trace_lock;
 +#else
 +return g_static_mutex_get_mutex(trace_lock);
 +#endif
 +}


I'd group mutex definition above with all the functions accessing it,
and also make the functions inline.

Well, to my taste, this is a good example where #define is better than
an inline function.  Compare the above with:

diff --git a/trace/simple.c b/trace/simple.c
index 1e3f691..2e55ac1 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -39,7 +39,17 @@
  * Trace records are written out by a dedicated thread.  The thread waits for
  * records to become available, writes them out, and then waits again.
  */
+#if GLIB_CHECK_VERSION(2, 32, 0)
+static GMutex trace_lock;
+#define lock_trace_lock() g_mutex_lock(trace_lock)
+#define unlock_trace_lock() g_mutex_unlock(trace_lock)
+#define get_trace_lock_mutex() (trace_lock)
+#else
 static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
+#define lock_trace_lock() g_static_mutex_lock(trace_lock)
+#define unlock_trace_lock() g_static_mutex_unlock(trace_lock)
+#define get_trace_lock_mutex() g_static_mutex_get_mutex(trace_lock)
+#endif

 /* g_cond_new() was deprecated in glib 2.31 but we still need to support it */
 #if GLIB_CHECK_VERSION(2, 31, 0)

(#defines here and elsewhere has added bonus - when debugging, debugger
does not step into the inline functions, -- such stepping is quite annoying).

But somehow many developers prefer inline functions (sometimes it is better
indeed, especially in a commonly used header files, and when the functions
has complex or many parameters; in this case we have much simpler situation.

For fun, this #ifdeffery is 5 times larger than the actual users of the
functions being defined :)

Thanks,

/mjt