Revert "virthread: Introduce virRWLockInitPreferWriter"

This reverts commit 328bd244.

As it turns out, this is not portable and very Linux & glibc
specific. Worse, this may lead to not starving writers on Linux
but everywhere else. Revert this and if the starvation occurs
resolve it.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrange <berrange@redhat.com>

src/libvirt_private.syms

@@ -2733,7 +2733,6 @@ virMutexUnlock;
 virOnce;
 virRWLockDestroy;
 virRWLockInit;
-virRWLockInitPreferWriter;
 virRWLockRead;
 virRWLockUnlock;
 virRWLockWrite;

src/util/virobject.c

@@ -275,7 +275,7 @@ virObjectRWLockableNew(virClassPtr klass)
     if (!(obj = virObjectNew(klass)))
         return NULL;
 
-    if (virRWLockInitPreferWriter(&obj->lock) < 0) {
+    if (virRWLockInit(&obj->lock) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("Unable to initialize RW lock"));
         virObjectUnref(obj);

src/util/virthread.c

@@ -95,15 +95,6 @@ void virMutexUnlock(virMutexPtr m)
 }
 
 
-/**
- * virRWLockInit:
- * @m: rwlock to init
- *
- * Initializes RW lock using pthread default attributes (which
- * is PTHREAD_RWLOCK_PREFER_READER_NP).
- *
- * Returns 0 on success, -1 otherwise.
- */
 int virRWLockInit(virRWLockPtr m)
 {
     int ret;
@@ -115,32 +106,6 @@ int virRWLockInit(virRWLockPtr m)
     return 0;
 }
 
-
-/**
- * virRWLockInitPreferWriter:
- * @m: rwlock to init
- *
- * Initializes RW lock which prefers writers over readers.
- *
- * Returns 0 on success, -1 otherwise.
- */
-int virRWLockInitPreferWriter(virRWLockPtr m)
-{
-    int ret;
-    pthread_rwlockattr_t attr;
-
-    pthread_rwlockattr_init(&attr);
-    pthread_rwlockattr_setkind_np(&attr, PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP);
-    ret = pthread_rwlock_init(&m->lock, &attr);
-    pthread_rwlockattr_destroy(&attr);
-    if (ret != 0) {
-        errno = ret;
-        return -1;
-    }
-    return 0;
-}
-
-
 void virRWLockDestroy(virRWLockPtr m)
 {
     pthread_rwlock_destroy(&m->lock);

src/util/virthread.h

@@ -136,7 +136,6 @@ void virMutexUnlock(virMutexPtr m);
 
 
 int virRWLockInit(virRWLockPtr m) ATTRIBUTE_RETURN_CHECK;
-int virRWLockInitPreferWriter(virRWLockPtr m) ATTRIBUTE_RETURN_CHECK;
 void virRWLockDestroy(virRWLockPtr m);
 
 void virRWLockRead(virRWLockPtr m);