On Thu, Nov 15, 2018 at 06:07:59PM +0800, Wei Wang wrote: > The bitmap mutex is used to synchronize threads to update the dirty > bitmap and the migration_dirty_pages counter. For example, the free > page optimization clears bits of free pages from the bitmap in an > iothread context. This patch makes migration_bitmap_clear_dirty update > the bitmap and counter under the mutex. > > Signed-off-by: Wei Wang <wei.w.w...@intel.com> > CC: Dr. David Alan Gilbert <dgilb...@redhat.com> > CC: Juan Quintela <quint...@redhat.com> > CC: Michael S. Tsirkin <m...@redhat.com> > CC: Peter Xu <pet...@redhat.com> > --- > migration/ram.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/migration/ram.c b/migration/ram.c > index 7e7deec..ef69dbe 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -1556,11 +1556,14 @@ static inline bool > migration_bitmap_clear_dirty(RAMState *rs, > { > bool ret; > > + qemu_mutex_lock(&rs->bitmap_mutex); > ret = test_and_clear_bit(page, rb->bmap); > > if (ret) { > rs->migration_dirty_pages--; > } > + qemu_mutex_unlock(&rs->bitmap_mutex); > + > return ret; > }
It seems fine to me, but have you thought about test_and_clear_bit_atomic()? Note that we just had test_and_set_bit_atomic() a few months ago. And not related to this patch: I'm unclear on why we have had bitmap_mutex before, since it seems unnecessary. Regards, -- Peter Xu