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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.gmail.com with ESMTPSA id s8sm28983697wrn.97.2021.03.29.02.42.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Mar 2021 02:42:14 -0700 (PDT) Subject: Re: [PATCH] replay: fix recursive checkpoints To: Pavel Dovgalyuk , qemu-devel@nongnu.org References: <161700476500.1140362.10108444973730452257.stgit@pasha-ThinkPad-X280> From: Paolo Bonzini Message-ID: Date: Mon, 29 Mar 2021 11:42:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <161700476500.1140362.10108444973730452257.stgit@pasha-ThinkPad-X280> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: alex.bennee@linaro.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 29/03/21 09:59, Pavel Dovgalyuk wrote: > Record/replay uses checkpoints to synchronize the execution > of the threads and timers. Hardware events such as BH are > processed at the checkpoints too. > Event processing can cause refreshing the virtual timers > and calling the icount-related functions, that also use checkpoints. > This patch prevents recursive processing of such checkpoints, > because they have their own records in the log and should be > processed later. > > Signed-off-by: Pavel Dovgalyuk > --- > replay/replay.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/replay/replay.c b/replay/replay.c > index c806fec69a..6df2abc18c 100644 > --- a/replay/replay.c > +++ b/replay/replay.c > @@ -180,12 +180,13 @@ bool replay_checkpoint(ReplayCheckpoint checkpoint) > } > > if (in_checkpoint) { > - /* If we are already in checkpoint, then there is no need > - for additional synchronization. > + /* > Recursion occurs when HW event modifies timers. > - Timer modification may invoke the checkpoint and > - proceed to recursion. */ > - return true; > + Prevent performing icount warp in this case and > + wait for another invocation of the checkpoint. > + */ > + g_assert(replay_mode == REPLAY_MODE_PLAY); > + return false; > } > in_checkpoint = true; > > Queued, thanks. Paolo