[Qemu-devel] [PATCH 01/11] migration: No need to take rcu during sync_dirty_bitmap

[Peter Xu]

cpu_physical_memory_sync_dirty_bitmap() has one RAMBlock* as
parameter, which means that it must be with RCU read lock held
already.  Taking it again inside seems redundant.  Removing it.
Instead comment on the functions about the RCU read lock.

Signed-off-by: Peter Xu <address@hidden>
---
 include/exec/ram_addr.h | 5 +----
 migration/ram.c         | 1 +
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 139ad79390..993fb760f3 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -408,6 +408,7 @@ static inline void 
cpu_physical_memory_clear_dirty_range(ram_addr_t start,
 }
 
 
+/* Must be with rcu read lock held */
 static inline
 uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
                                                ram_addr_t start,
@@ -431,8 +432,6 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
                                         DIRTY_MEMORY_BLOCK_SIZE);
         unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS);
 
-        rcu_read_lock();
-
         src = atomic_rcu_read(
                 &ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION])->blocks;
 
@@ -452,8 +451,6 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
                 idx++;
             }
         }
-
-        rcu_read_unlock();
     } else {
         ram_addr_t offset = rb->offset;
 
diff --git a/migration/ram.c b/migration/ram.c
index 1ca9ba77b6..3e11806ccd 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1680,6 +1680,7 @@ static inline bool migration_bitmap_clear_dirty(RAMState 
*rs,
     return ret;
 }
 
+/* Must be with rcu read lock held */
 static void migration_bitmap_sync_range(RAMState *rs, RAMBlock *rb,
                                         ram_addr_t start, ram_addr_t length)
 {
-- 
2.17.1