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d="scan'208";a="4978399" From: Paul Durrant To: Anthony Perard , "qemu-devel@nongnu.org" Thread-Topic: [PATCH v2 1/2] xen-bus: Fix backend state transition on device reset Thread-Index: AQHVWZu40FkCyruIxkOY4hQyauVsBKcOxNHg Date: Tue, 27 Aug 2019 09:44:48 +0000 Message-ID: References: <20190823101534.465-1-anthony.perard@citrix.com> <20190823101534.465-2-anthony.perard@citrix.com> In-Reply-To: <20190823101534.465-2-anthony.perard@citrix.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: FreeBSD 9.x X-Received-From: 216.71.155.175 Subject: Re: [Qemu-devel] [PATCH v2 1/2] xen-bus: Fix backend state transition on device reset 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: Anthony Perard , "xen-devel@lists.xenproject.org" , Stefano Stabellini , "qemu-stable@nongnu.org" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > -----Original Message----- > From: Anthony PERARD > Sent: 23 August 2019 11:16 > To: qemu-devel@nongnu.org > Cc: Anthony Perard ; qemu-stable@nongnu.org; S= tefano Stabellini > ; Paul Durrant ; xen-dev= el@lists.xenproject.org > Subject: [PATCH v2 1/2] xen-bus: Fix backend state transition on device r= eset >=20 > When a frontend wants to reset its state and the backend one, it > starts with setting "Closing", then waits for the backend (QEMU) to do > the same. >=20 > But when QEMU is setting "Closing" to its state, it triggers an event > (xenstore watch) that re-execute xen_device_backend_changed() and set > the backend state to "Closed". QEMU should wait for the frontend to > set "Closed" before doing the same. >=20 > Before setting "Closed" to the backend_state, we are also going to > check if there is a frontend. If that the case, when the backend state > is set to "Closing" the frontend should react and sets its state to > "Closing" then "Closed". The backend should wait for that to happen. >=20 > Fixes: b6af8926fb858c4f1426e5acb2cfc1f0580ec98a > Signed-off-by: Anthony PERARD Reviewed-by: Paul Durrant > --- > Cc: qemu-stable@nongnu.org > --- >=20 > Notes: > v2: > - use a helper > - Add InitWait and Initialised to the list of active state >=20 > hw/xen/xen-bus.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) >=20 > diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c > index e40500242d..62c127b926 100644 > --- a/hw/xen/xen-bus.c > +++ b/hw/xen/xen-bus.c > @@ -516,6 +516,23 @@ static void xen_device_backend_set_online(XenDevice = *xendev, bool online) > xen_device_backend_printf(xendev, "online", "%u", online); > } >=20 > +/* > + * Tell from the state whether the frontend is likely alive, > + * i.e. it will react to a change of state of the backend. > + */ > +static bool xen_device_state_is_active(enum xenbus_state state) > +{ > + switch (state) { > + case XenbusStateInitWait: > + case XenbusStateInitialised: > + case XenbusStateConnected: > + case XenbusStateClosing: > + return true; > + default: > + return false; > + } > +} > + > static void xen_device_backend_changed(void *opaque) > { > XenDevice *xendev =3D opaque; > @@ -539,11 +556,11 @@ static void xen_device_backend_changed(void *opaque= ) >=20 > /* > * If the toolstack (or unplug request callback) has set the backend > - * state to Closing, but there is no active frontend (i.e. the > - * state is not Connected) then set the backend state to Closed. > + * state to Closing, but there is no active frontend then set the > + * backend state to Closed. > */ > if (xendev->backend_state =3D=3D XenbusStateClosing && > - xendev->frontend_state !=3D XenbusStateConnected) { > + !xen_device_state_is_active(state)) { > xen_device_backend_set_state(xendev, XenbusStateClosed); > } >=20 > -- > Anthony PERARD