From: Olivier Houchard <ohouchard@haproxy.com>
Date: Wed, 26 Mar 2025 12:11:30 +0000 (+0000)
Subject: MINOR: threads: Add HA_RWLOCK_TRYRDTOWR()
X-Git-Tag: v3.2-dev9~26
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ba521a1d883b4f996e2bda3b773521be8a5d8c90;p=thirdparty%2Fhaproxy.git

MINOR: threads: Add HA_RWLOCK_TRYRDTOWR()

Add HA_RWLOCK_TRYRDTOWR(), that tries to upgrade a lock
from reader to writer, and fails if any seeker or writer already
holds it.
---

diff --git a/include/haproxy/thread.h b/include/haproxy/thread.h
index d99146766..c71cd25ab 100644
--- a/include/haproxy/thread.h
+++ b/include/haproxy/thread.h
@@ -87,6 +87,7 @@ enum { tgid = 1 };
 #define HA_RWLOCK_SKUNLOCK(lbl,l)       do { /* do nothing */ } while(0)
 #define HA_RWLOCK_TRYSKLOCK(lbl,l)      ({ 0; })
 #define HA_RWLOCK_TRYRDTOSK(lbl,l)      ({ 0; })
+#define HA_RWLOCK_TRYRDTOWR(lbl,l)      ({ 0; })
 
 #define ha_sigmask(how, set, oldset)  sigprocmask(how, set, oldset)
 
@@ -327,6 +328,7 @@ static inline unsigned long thread_isolated()
 #define HA_RWLOCK_SKUNLOCK(lbl,l)       pl_drop_s(l)      /* S --> N */
 #define HA_RWLOCK_TRYSKLOCK(lbl,l)      (!pl_try_s(l))    /* N -?> S */
 #define HA_RWLOCK_TRYRDTOSK(lbl,l)      (!pl_try_rtos(l)) /* R -?> S */
+#define HA_RWLOCK_TRYRDTOWR(lbl, l)     (!pl_try_rtow(l)) /* R -?> W */
 
 #else /* !defined(DEBUG_THREAD) && !defined(DEBUG_FULL) */
 
@@ -356,6 +358,7 @@ static inline unsigned long thread_isolated()
 #define __RWLOCK_SKUNLOCK(l)       pl_drop_s(l)      /* S --> N */
 #define __RWLOCK_TRYSKLOCK(l)      (!pl_try_s(l))    /* N -?> S */
 #define __RWLOCK_TRYRDTOSK(l)      (!pl_try_rtos(l)) /* R -?> S */
+#define __RWLOCK_TRYRDTOWR(l)      (!pl_try_rtow(l)) /* R -?> W */
 
 #define HA_SPIN_INIT(l)            __spin_init(l)
 #define HA_SPIN_DESTROY(l)         __spin_destroy(l)
@@ -381,6 +384,7 @@ static inline unsigned long thread_isolated()
 #define HA_RWLOCK_SKUNLOCK(lbl,l)  __ha_rwlock_skunlock(lbl, l, __func__, __FILE__, __LINE__)
 #define HA_RWLOCK_TRYSKLOCK(lbl,l) __ha_rwlock_trysklock(lbl, l, __func__, __FILE__, __LINE__)
 #define HA_RWLOCK_TRYRDTOSK(lbl,l) __ha_rwlock_tryrdtosk(lbl, l, __func__, __FILE__, __LINE__)
+#define HA_RWLOCK_TRYRDTOWR(lbl,l) __ha_rwlock_tryrdtowr(lbl, l, __func__, __FILE__, __LINE__)
 
 /* Following functions are used to collect some stats about locks. We wrap
  * pthread functions to known how much time we wait in a lock. */
@@ -413,6 +417,8 @@ int __ha_rwlock_trysklock(enum lock_label lbl, struct ha_rwlock *l,
                           const char *func, const char *file, int line);
 int __ha_rwlock_tryrdtosk(enum lock_label lbl, struct ha_rwlock *l,
                           const char *func, const char *file, int line);
+int __ha_rwlock_tryrdtowr(enum lock_label lbl, struct ha_rwlock *l,
+                          const char *func, const char *file, int line);
 void __spin_init(struct ha_spinlock *l);
 void __spin_destroy(struct ha_spinlock *l);
 void __spin_lock(enum lock_label lbl, struct ha_spinlock *l,
diff --git a/src/thread.c b/src/thread.c
index 3ca0b5a4e..4b3e72b20 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -998,6 +998,46 @@ int __ha_rwlock_tryrdtosk(enum lock_label lbl, struct ha_rwlock *l,
 	return r;
 }
 
+int __ha_rwlock_tryrdtowr(enum lock_label lbl, struct ha_rwlock *l,
+                          const char *func, const char *file, int line)
+{
+	ulong tbit = (ti && ti->ltid_bit) ? ti->ltid_bit : 1;
+	struct ha_rwlock_state *st = &l->info.st[tgid-1];
+	uint64_t start_time;
+	uint bucket;
+	int r;
+
+	if ((st->cur_writer | st->cur_seeker) & tbit)
+		abort();
+
+	if (!(st->cur_readers & tbit))
+		abort();
+
+	HA_ATOMIC_OR(&st->wait_writers, tbit);
+
+	start_time = -now_mono_time();
+	r = __RWLOCK_TRYRDTOWR(&l->lock);
+	start_time += now_mono_time();
+
+	if (likely(!r)) {
+		/* got the lock ! */
+		HA_ATOMIC_ADD(&lock_stats_sk[lbl].nsec_wait, start_time);
+
+		start_time &= 0x3fffffff; // keep values below 1 billion only
+		bucket = flsnz((uint32_t)start_time ? (uint32_t)start_time : 1) - 1;
+		HA_ATOMIC_INC(&lock_stats_sk[lbl].buckets[bucket]);
+		HA_ATOMIC_OR(&st->cur_writer, tbit);
+		HA_ATOMIC_AND(&st->cur_readers, ~tbit);
+		l->info.last_location.function = func;
+		l->info.last_location.file     = file;
+		l->info.last_location.line     = line;
+	}
+
+	HA_ATOMIC_AND(&st->wait_writers, ~tbit);
+	return r;
+}
+
+
 void __spin_init(struct ha_spinlock *l)
 {
 	memset(l, 0, sizeof(struct ha_spinlock));