diff mbox

[PULL,33/62] memory: make cpu_physical_memory_sync_dirty_bitmap() fully atomic

Message ID 1433517363-32335-34-git-send-email-pbonzini@redhat.com
State New
Headers show

Commit Message

Paolo Bonzini June 5, 2015, 3:15 p.m. UTC 
From: Stefan Hajnoczi <stefanha@redhat.com>

The fast path of cpu_physical_memory_sync_dirty_bitmap() directly
manipulates the dirty bitmap.  Use atomic_xchg() to make the
test-and-clear atomic.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <1417519399-3166-7-git-send-email-stefanha@redhat.com>
[Only do xchg on nonzero words. - Paolo]
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/exec/ram_addr.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
diff mbox

Patch

diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index a2beea7..c113f21 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -224,12 +224,12 @@  uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned long *dest,
 
         for (k = page; k < page + nr; k++) {
             if (src[k]) {
+                unsigned long bits = atomic_xchg(&src[k], 0);
                 unsigned long new_dirty;
                 new_dirty = ~dest[k];
-                dest[k] |= src[k];
-                new_dirty &= src[k];
+                dest[k] |= bits;
+                new_dirty &= bits;
                 num_dirty += ctpopl(new_dirty);
-                src[k] = 0;
             }
         }
     } else {