[nginx] Introduced ngx_rwlock_downgrade().

[Ruslan Ermilov]

details:   http://hg.nginx.org/nginx/rev/d1816a2696de
branches:  
changeset: 7038:d1816a2696de
user:      Ruslan Ermilov <ru at nginx.com>
date:      Fri Jun 16 18:15:58 2017 +0300
description:
Introduced ngx_rwlock_downgrade().

diffstat:

 src/core/ngx_rwlock.c |  9 +++++++++
 src/core/ngx_rwlock.h |  1 +
 2 files changed, 10 insertions(+), 0 deletions(-)

diffs (30 lines):

diff -r 12efcdcb8a4b -r d1816a2696de src/core/ngx_rwlock.c
--- a/src/core/ngx_rwlock.c	Fri Jun 16 18:15:53 2017 +0300
+++ b/src/core/ngx_rwlock.c	Fri Jun 16 18:15:58 2017 +0300
@@ -109,6 +109,15 @@ ngx_rwlock_unlock(ngx_atomic_t *lock)
 }
 
 
+void
+ngx_rwlock_downgrade(ngx_atomic_t *lock)
+{
+    if (*lock == NGX_RWLOCK_WLOCK) {
+        *lock = 1;
+    }
+}
+
+
 #else
 
 #if (NGX_HTTP_UPSTREAM_ZONE || NGX_STREAM_UPSTREAM_ZONE)
diff -r 12efcdcb8a4b -r d1816a2696de src/core/ngx_rwlock.h
--- a/src/core/ngx_rwlock.h	Fri Jun 16 18:15:53 2017 +0300
+++ b/src/core/ngx_rwlock.h	Fri Jun 16 18:15:58 2017 +0300
@@ -16,6 +16,7 @@
 void ngx_rwlock_wlock(ngx_atomic_t *lock);
 void ngx_rwlock_rlock(ngx_atomic_t *lock);
 void ngx_rwlock_unlock(ngx_atomic_t *lock);
+void ngx_rwlock_downgrade(ngx_atomic_t *lock);
 
 
 #endif /* _NGX_RWLOCK_H_INCLUDED_ */