From 64fbffbbaaeeb6185eba84bccd2f981bee23710d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@sury.org>
Date: Thu, 16 Aug 2018 15:03:42 +0200
Subject: [PATCH] Use simple pthread_rwlock in place of our custom adaptive
 rwlock

---
 config.h.in                  |  3 ++
 configure                    | 15 +++++---
 configure.ac                 |  6 +--
 lib/isc/include/isc/rwlock.h | 11 ++++++
 lib/isc/rwlock.c             | 74 ++++++++++++++++++++++++++++++++++++
 5 files changed, 99 insertions(+), 10 deletions(-)

diff --git a/config.h.in b/config.h.in
index 4f40e31458..cf742bc31c 100644
--- a/config.h.in
+++ b/config.h.in
@@ -309,6 +309,9 @@
 /* Have PTHREAD_PRIO_INHERIT. */
 #undef HAVE_PTHREAD_PRIO_INHERIT
 
+/* Define to 1 if you have the `pthread_rwlock_rdlock' function. */
+#undef HAVE_PTHREAD_RWLOCK_RDLOCK
+
 /* Define to 1 if you have the `pthread_setaffinity_np' function. */
 #undef HAVE_PTHREAD_SETAFFINITY_NP
 
diff --git a/configure b/configure
index 09167c62f4..24cca62c9c 100755
--- a/configure
+++ b/configure
@@ -15615,12 +15615,17 @@ $as_echo "no" >&6; }
 esac
 
 
-#
-# If PIC is disabled, shared libraries must also be
-#
-if test "$pic_mode" = "no"; then :
-  enable_shared="no"
+for ac_func in pthread_rwlock_rdlock
+do :
+  ac_fn_c_check_func "$LINENO" "pthread_rwlock_rdlock" "ac_cv_func_pthread_rwlock_rdlock"
+if test "x$ac_cv_func_pthread_rwlock_rdlock" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PTHREAD_RWLOCK_RDLOCK 1
+_ACEOF
+
 fi
+done
+
 
 CRYPTO=OpenSSL
 
diff --git a/configure.ac b/configure.ac
index 1e20f1724e..272706314e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -733,11 +733,7 @@ case $use_libtool in
 esac
 AC_SUBST(INSTALL_LIBRARY)
 
-#
-# If PIC is disabled, shared libraries must also be
-#
-AS_IF([test "$pic_mode" = "no"],
-      [enable_shared="no"])
+AC_CHECK_FUNCS([pthread_rwlock_rdlock])
 
 CRYPTO=OpenSSL
 
diff --git a/lib/isc/include/isc/rwlock.h b/lib/isc/include/isc/rwlock.h
index ed1ff66312..50d06d72d0 100644
--- a/lib/isc/include/isc/rwlock.h
+++ b/lib/isc/include/isc/rwlock.h
@@ -14,6 +14,7 @@
 #define ISC_RWLOCK_H 1
 
 #include <inttypes.h>
+#include <pthread.h>
 
 /*! \file isc/rwlock.h */
 
@@ -31,6 +32,14 @@ typedef enum {
 	isc_rwlocktype_write
 } isc_rwlocktype_t;
 
+#if HAVE_PTHREAD_RWLOCK_RDLOCK
+
+struct isc_rwlock {
+	pthread_rwlock_t	rwlock;
+};
+
+#else /* HAVE_PTHREAD_RWLOCK_RDLOCK */
+
 struct isc_rwlock {
 	/* Unlocked. */
 	unsigned int		magic;
@@ -68,6 +77,8 @@ struct isc_rwlock {
 
 };
 
+#endif /* HAVE_PTHREAD_RWLOCK_RDLOCK */
+
 isc_result_t
 isc_rwlock_init(isc_rwlock_t *rwl, unsigned int read_quota,
 		unsigned int write_quota);
diff --git a/lib/isc/rwlock.c b/lib/isc/rwlock.c
index 1071fecc07..2619619d1b 100644
--- a/lib/isc/rwlock.c
+++ b/lib/isc/rwlock.c
@@ -27,6 +27,78 @@
 #include <isc/rwlock.h>
 #include <isc/util.h>
 
+#if HAVE_PTHREAD_RWLOCK_RDLOCK
+
+#include <errno.h>
+#include <pthread.h>
+
+isc_result_t
+isc_rwlock_init(isc_rwlock_t *rwl, unsigned int read_quota,
+		unsigned int write_quota)
+{
+	UNUSED(read_quota);
+	UNUSED(write_quota);
+	REQUIRE(pthread_rwlock_init(&rwl->rwlock, NULL) == 0);
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
+	switch (type) {
+	case isc_rwlocktype_read: REQUIRE(pthread_rwlock_rdlock(&rwl->rwlock) == 0); break;
+	case isc_rwlocktype_write: REQUIRE(pthread_rwlock_wrlock(&rwl->rwlock) == 0); break;
+	default: INSIST(0);
+	}
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
+	int ret = 0;
+	switch (type) {
+	case isc_rwlocktype_read:
+		ret = pthread_rwlock_tryrdlock(&rwl->rwlock);
+		break;
+	case isc_rwlocktype_write:
+		ret = pthread_rwlock_trywrlock(&rwl->rwlock);
+		break;
+	default: INSIST(0);
+	}
+
+	switch (ret) {
+	case 0: return (ISC_R_SUCCESS);
+	case EBUSY: return (ISC_R_LOCKBUSY);
+	case EAGAIN: return (ISC_R_LOCKBUSY);
+	default: INSIST(0); ISC_UNREACHABLE();
+	}
+}
+
+
+isc_result_t
+isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
+	UNUSED(type);
+	REQUIRE(pthread_rwlock_unlock(&rwl->rwlock) == 0);
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_rwlock_tryupgrade(isc_rwlock_t *rwl) {
+	return (ISC_R_LOCKBUSY);
+}
+
+void
+isc_rwlock_downgrade(isc_rwlock_t *rwl) {
+	isc_rwlock_unlock(rwl, isc_rwlocktype_write);
+	isc_rwlock_lock(rwl, isc_rwlocktype_read);
+}
+
+void
+isc_rwlock_destroy(isc_rwlock_t *rwl) {
+	pthread_rwlock_destroy(&rwl->rwlock);
+}
+
+#else
+
 #define RWLOCK_MAGIC		ISC_MAGIC('R', 'W', 'L', 'k')
 #define VALID_RWLOCK(rwl)	ISC_MAGIC_VALID(rwl, RWLOCK_MAGIC)
 
@@ -549,3 +621,5 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
 
 	return (ISC_R_SUCCESS);
 }
+
+#endif /* HAVE_PTHREAD_RWLOCK_RDLOCK */