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That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Dmitry Fleytman , "Michael S. Tsirkin" , Jason Wang , Li Qiang , Qemu Developers , Alexander Bulekov , Gerd Hoffmann , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Michael Tokarev =E4=BA=8E2020=E5=B9=B49=E6=9C=883=E6=97=A5= =E5=91=A8=E5=9B=9B =E4=B8=8B=E5=8D=881:12=E5=86=99=E9=81=93=EF=BC=9A > > 02.09.2020 19:22, Li Qiang wrote: > .. > > @@ -809,6 +809,10 @@ void virtio_gpu_process_cmdq(VirtIOGPU *g) > > { > > struct virtio_gpu_ctrl_command *cmd; > > > > + if (atomic_read(&g->in_io)) { > > + return; > > + } > > + atomic_set(&g->in_io, 1); > > Can't we race in these two instructions? Both > threads atomic_reads at the same time, both see zero, > and both are trying to set it to 1, no? > > Just asking really, b/c despite of the atomic_ prefix, > to me this look a bit unsafe.. Yes you're right. My patch is wrong. Here I try to address race condition and DMA to MMIO issue at the same time. I will first focus the DMA to MMIO issue in the revision patch. Thanks, Li Qiang > > Thanks, > > /mjt