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Wed, 18 Sep 2024 14:13:30 -0700 (PDT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Alex=20Benn=C3=A9e?= , Elisha Hollander , Pierrick Bouvier , Paolo Bonzini Subject: [PULL 14/18] util/timer: avoid deadlock when shutting down Date: Wed, 18 Sep 2024 22:07:08 +0100 Message-Id: <20240918210712.2336854-15-alex.bennee@linaro.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20240918210712.2336854-1-alex.bennee@linaro.org> References: <20240918210712.2336854-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::62c; envelope-from=alex.bennee@linaro.org; helo=mail-ej1-x62c.google.com 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, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1726694023570116600 When we shut down a guest we disable the timers. However this can cause deadlock if the guest has queued some async work that is trying to advance system time and spins forever trying to wind time forward. Pay attention to the return code and bail early if we can't wind time forward. Reported-by: Elisha Hollander Signed-off-by: Alex Benn=C3=A9e Reviewed-by: Pierrick Bouvier Message-Id: <20240916085400.1046925-15-alex.bennee@linaro.org> diff --git a/util/qemu-timer.c b/util/qemu-timer.c index 213114be68..6b1533bc2a 100644 --- a/util/qemu-timer.c +++ b/util/qemu-timer.c @@ -685,10 +685,17 @@ int64_t qemu_clock_advance_virtual_time(int64_t dest) { int64_t clock =3D qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); AioContext *aio_context; + int64_t deadline; + aio_context =3D qemu_get_aio_context(); - while (clock < dest) { - int64_t deadline =3D qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL, + + deadline =3D qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL, QEMU_TIMER_ATTR_ALL); + /* + * A deadline of < 0 indicates this timer is not enabled, so we + * won't get far trying to run it forward. + */ + while (deadline >=3D 0 && clock < dest) { int64_t warp =3D qemu_soonest_timeout(dest - clock, deadline); =20 qemu_virtual_clock_set_ns(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + = warp); @@ -696,6 +703,9 @@ int64_t qemu_clock_advance_virtual_time(int64_t dest) qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL); timerlist_run_timers(aio_context->tlg.tl[QEMU_CLOCK_VIRTUAL]); clock =3D qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + + deadline =3D qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL, + QEMU_TIMER_ATTR_ALL); } qemu_clock_notify(QEMU_CLOCK_VIRTUAL); =20 --=20 2.39.5