Re: [RFC 12/26] rcu: Make rcu_read_lock & rcu_read_unlock not inline

[Paolo Bonzini]

On 8/7/25 14:30, Zhao Liu wrote:
Make rcu_read_lock & rcu_read_unlock not inline, then bindgen could
generate the bindings.
Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Zhao Liu <zhao1....@intel.com>

Either this, or keep it inline and add wrappers rust_rcu_read_lock() and 
rust_rcu_read_unlock().

Paolo

---
  include/qemu/rcu.h | 45 ++-------------------------------------------
  util/rcu.c         | 43 +++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 45 insertions(+), 43 deletions(-)

diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h
index 020dbe4d8b77..34d955204b81 100644
--- a/include/qemu/rcu.h
+++ b/include/qemu/rcu.h
@@ -75,49 +75,8 @@ struct rcu_reader_data {
  
  QEMU_DECLARE_CO_TLS(struct rcu_reader_data, rcu_reader)
  
-static inline void rcu_read_lock(void)
-{
-    struct rcu_reader_data *p_rcu_reader = get_ptr_rcu_reader();
-    unsigned ctr;
-
-    if (p_rcu_reader->depth++ > 0) {
-        return;
-    }
-
-    ctr = qatomic_read(&rcu_gp_ctr);
-    qatomic_set(&p_rcu_reader->ctr, ctr);
-
-    /*
-     * Read rcu_gp_ptr and write p_rcu_reader->ctr before reading
-     * RCU-protected pointers.
-     */
-    smp_mb_placeholder();
-}
-
-static inline void rcu_read_unlock(void)
-{
-    struct rcu_reader_data *p_rcu_reader = get_ptr_rcu_reader();
-
-    assert(p_rcu_reader->depth != 0);
-    if (--p_rcu_reader->depth > 0) {
-        return;
-    }
-
-    /* Ensure that the critical section is seen to precede the
-     * store to p_rcu_reader->ctr.  Together with the following
-     * smp_mb_placeholder(), this ensures writes to p_rcu_reader->ctr
-     * are sequentially consistent.
-     */
-    qatomic_store_release(&p_rcu_reader->ctr, 0);
-
-    /* Write p_rcu_reader->ctr before reading p_rcu_reader->waiting.  */
-    smp_mb_placeholder();
-    if (unlikely(qatomic_read(&p_rcu_reader->waiting))) {
-        qatomic_set(&p_rcu_reader->waiting, false);
-        qemu_event_set(&rcu_gp_event);
-    }
-}
-
+void rcu_read_lock(void);
+void rcu_read_unlock(void);
  void synchronize_rcu(void);
  
  /*
diff --git a/util/rcu.c b/util/rcu.c
index b703c86f15a3..2dfd82796e1e 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -141,6 +141,49 @@ static void wait_for_readers(void)
      QLIST_SWAP(&registry, &qsreaders, node);
  }
  
+void rcu_read_lock(void)
+{
+    struct rcu_reader_data *p_rcu_reader = get_ptr_rcu_reader();
+    unsigned ctr;
+
+    if (p_rcu_reader->depth++ > 0) {
+        return;
+    }
+
+    ctr = qatomic_read(&rcu_gp_ctr);
+    qatomic_set(&p_rcu_reader->ctr, ctr);
+
+    /*
+     * Read rcu_gp_ptr and write p_rcu_reader->ctr before reading
+     * RCU-protected pointers.
+     */
+    smp_mb_placeholder();
+}
+
+void rcu_read_unlock(void)
+{
+    struct rcu_reader_data *p_rcu_reader = get_ptr_rcu_reader();
+
+    assert(p_rcu_reader->depth != 0);
+    if (--p_rcu_reader->depth > 0) {
+        return;
+    }
+
+    /* Ensure that the critical section is seen to precede the
+     * store to p_rcu_reader->ctr.  Together with the following
+     * smp_mb_placeholder(), this ensures writes to p_rcu_reader->ctr
+     * are sequentially consistent.
+     */
+    qatomic_store_release(&p_rcu_reader->ctr, 0);
+
+    /* Write p_rcu_reader->ctr before reading p_rcu_reader->waiting.  */
+    smp_mb_placeholder();
+    if (unlikely(qatomic_read(&p_rcu_reader->waiting))) {
+        qatomic_set(&p_rcu_reader->waiting, false);
+        qemu_event_set(&rcu_gp_event);
+    }
+}
+
  void synchronize_rcu(void)
  {
      QEMU_LOCK_GUARD(&rcu_sync_lock);