From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52933) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gRW7Y-00081T-47 for qemu-devel@nongnu.org; Tue, 27 Nov 2018 00:41:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gRW7S-0007RA-F3 for qemu-devel@nongnu.org; Tue, 27 Nov 2018 00:41:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47816) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gRW7S-0007Qj-AJ for qemu-devel@nongnu.org; Tue, 27 Nov 2018 00:41:10 -0500 Date: Tue, 27 Nov 2018 13:40:56 +0800 From: Peter Xu Message-ID: <20181127054056.GA3205@xz-x1> References: <1542276484-25508-1-git-send-email-wei.w.wang@intel.com> <1542276484-25508-4-git-send-email-wei.w.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1542276484-25508-4-git-send-email-wei.w.wang@intel.com> Subject: Re: [Qemu-devel] [PATCH v9 3/8] migration: use bitmap_mutex in migration_bitmap_clear_dirty List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wei Wang Cc: qemu-devel@nongnu.org, virtio-dev@lists.oasis-open.org, mst@redhat.com, quintela@redhat.com, dgilbert@redhat.com, pbonzini@redhat.com, liliang.opensource@gmail.com, nilal@redhat.com, riel@redhat.com 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 > CC: Dr. David Alan Gilbert > CC: Juan Quintela > CC: Michael S. Tsirkin > CC: Peter Xu > --- > 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