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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [RFC PATCH v2 1/2] libs/light: add device model start timeout env var
On Thu, Apr 11, 2024 at 03:28:19PM +0300, Manos Pitsidianakis wrote:
> diff --git a/docs/man/xl.1.pod.in b/docs/man/xl.1.pod.in
> index bed8393473..c159877094 100644
> --- a/docs/man/xl.1.pod.in
> +++ b/docs/man/xl.1.pod.in
> @@ -1993,6 +1993,17 @@ Otherwise the build time default in
> LIBXL_BOOTLOADER_TIMEOUT will be used.
> If defined the value must be an unsigned integer between 0 and INT_MAX,
> otherwise behavior is undefined. Setting to 0 disables the timeout.
I don't think a value of "0" would disable timeouts, did you try?
It's more likely that the timeout will fire immediately. I'll had some
comment later about this on case-by-case basis.
>
> +=item LIBXL_DEVICE_MODEL_START_TIMEOUT
> +
> +Timeout in seconds for starting the device model process. Useful in case the
> +device model takes an unusual amount of time to start— for example in case of
Could you use only ASCII characters, here ^
It's looks like it's the first UTF-8 chr in this document, and we can do
without it. I just want to avoid find out later that something break
because of that chr.
> +very slow I/O, in case of slow performance due to memory sanitizer usage,
> etc.
> +
> +If undefined, the default hard-coded value of 60 seconds is used.
> +
> +If defined, the value must be an unsigned integer between 0 and INT_MAX,
> +otherwise behaviour is undefined. Setting the value to 0 disables the
> timeout.
> +
> =back
>
> =head1 SEE ALSO
> diff --git a/tools/libs/light/libxl_9pfs.c b/tools/libs/light/libxl_9pfs.c
> index 48f894f070..950a464b45 100644
> --- a/tools/libs/light/libxl_9pfs.c
> +++ b/tools/libs/light/libxl_9pfs.c
> @@ -132,7 +132,7 @@ static int xen9pfsd_spawn(libxl__egc *egc, uint32_t
> domid, libxl_device_p9 *p9,
> aop9->spawn.ao = aodev->ao;
> aop9->spawn.what = "xen-9pfs daemon";
> aop9->spawn.xspath = GCSPRINTF("%s/state", path);
> - aop9->spawn.timeout_ms = LIBXL_DEVICE_MODEL_START_TIMEOUT * 1000;
> + aop9->spawn.timeout_ms = __libxl_device_model_start_timeout() * 1000;
So this value is going to be used by libxl__spawn_spawn() then
libxl__xswait_start(), and it's looks like a timeout of "0" will have
the timeout fire immediately. Instead, a value of "-1" might disable the
timeout, but I don't know how well it would work without a timeout.
Timeout is setup with libxl__ev_time_register_rel().
> aop9->spawn.pidpath = GCSPRINTF("%s/pid", path);
> aop9->spawn.midproc_cb = libxl__spawn_record_pid;
> aop9->spawn.confirm_cb = xen9pfsd_confirm;
> diff --git a/tools/libs/light/libxl_device.c b/tools/libs/light/libxl_device.c
> index 6f0100d05e..452e55ba23 100644
> --- a/tools/libs/light/libxl_device.c
> +++ b/tools/libs/light/libxl_device.c
> @@ -1436,7 +1436,7 @@ int libxl__wait_for_device_model_deprecated(libxl__gc
> *gc,
>
> path = DEVICE_MODEL_XS_PATH(gc, dm_domid, domid, "/state");
> return libxl__xenstore_child_wait_deprecated(gc, domid,
> - LIBXL_DEVICE_MODEL_START_TIMEOUT,
> + __libxl_device_model_start_timeout(),
This function will return an error immediately, without trying, with a
timeout of "0", and "-1" isn't an option (well I guess it might be
INT_MAX because it an unsigned value).
> "Device Model", path, state, spawning,
> check_callback,
> check_callback_userdata);
> }
> diff --git a/tools/libs/light/libxl_dm.c b/tools/libs/light/libxl_dm.c
> index 0b03a7c747..4369fef161 100644
> --- a/tools/libs/light/libxl_dm.c
> +++ b/tools/libs/light/libxl_dm.c
> @@ -2629,7 +2629,7 @@ static void spawn_qmp_proxy(libxl__egc *egc,
> sdss->qmp_proxy_spawn.pidpath = GCSPRINTF("%s/image/qmp-proxy-pid",
> dom_path);
> sdss->qmp_proxy_spawn.xspath = DEVICE_MODEL_XS_PATH(gc,
> LIBXL_TOOLSTACK_DOMID,
> dm_domid,
> "/qmp-proxy-state");
> - sdss->qmp_proxy_spawn.timeout_ms = LIBXL_DEVICE_MODEL_START_TIMEOUT *
> 1000;
> + sdss->qmp_proxy_spawn.timeout_ms = __libxl_device_model_start_timeout()
> * 1000;
That's used by libxl__spawn_spawn(). Already commented on it.
> sdss->qmp_proxy_spawn.midproc_cb = libxl__spawn_record_pid;
> sdss->qmp_proxy_spawn.confirm_cb = qmp_proxy_confirm;
> sdss->qmp_proxy_spawn.failure_cb = qmp_proxy_startup_failed;
> @@ -3011,7 +3011,7 @@ retry_transaction:
> spawn->what = GCSPRINTF("domain %d device model", domid);
> spawn->xspath = DEVICE_MODEL_XS_PATH(gc, LIBXL_TOOLSTACK_DOMID, domid,
> "/state");
> - spawn->timeout_ms = LIBXL_DEVICE_MODEL_START_TIMEOUT * 1000;
> + spawn->timeout_ms = __libxl_device_model_start_timeout() * 1000;
That's used by libxl__spawn_spawn(). Already commented on it.
> spawn->pidpath = GCSPRINTF("%s/image/device-model-pid", dom_path);
> spawn->midproc_cb = libxl__spawn_record_pid;
> spawn->confirm_cb = device_model_confirm;
> @@ -3435,7 +3435,7 @@ void libxl__spawn_qdisk_backend(libxl__egc *egc,
> libxl__dm_spawn_state *dmss)
>
> dmss->spawn.what = GCSPRINTF("domain %u Qdisk backend", domid);
> dmss->spawn.xspath = GCSPRINTF("device-model/%u/state", domid);
> - dmss->spawn.timeout_ms = LIBXL_DEVICE_MODEL_START_TIMEOUT * 1000;
> + dmss->spawn.timeout_ms = __libxl_device_model_start_timeout() * 1000;
That's used by libxl__spawn_spawn(). Already commented on it.
> /*
> * We cannot save Qemu pid anywhere in the xenstore guest dir,
> * because we will call this from unprivileged driver domains,
> diff --git a/tools/libs/light/libxl_dom_suspend.c
> b/tools/libs/light/libxl_dom_suspend.c
> index 6091a5f3f6..29e51f6c40 100644
> --- a/tools/libs/light/libxl_dom_suspend.c
> +++ b/tools/libs/light/libxl_dom_suspend.c
> @@ -517,7 +517,7 @@ void libxl__dm_resume(libxl__egc *egc,
> rc = libxl__ev_time_register_rel(dmrs->ao,
> &dmrs->time,
> dm_resume_timeout,
> - LIBXL_DEVICE_MODEL_START_TIMEOUT *
> 1000);
> + __libxl_device_model_start_timeout() *
> 1000);
libxl__ev_time_register_rel() just setup a timer, and I think with a
timeout of 0, dm_resume_timeout() would be call immediately as soon as
the current function returns, resulting in a failure.
> if (rc) goto out;
>
> switch (libxl__device_model_version_running(gc, domid)) {
> diff --git a/tools/libs/light/libxl_internal.h
> b/tools/libs/light/libxl_internal.h
> index 803dbc1a03..684390f822 100644
> --- a/tools/libs/light/libxl_internal.h
> +++ b/tools/libs/light/libxl_internal.h
> @@ -97,6 +97,12 @@
> /* QEMU may be slow to load and start due to a bug in Linux where the I/O
> * subsystem sometime produce high latency under load. */
> #define LIBXL_DEVICE_MODEL_START_TIMEOUT 60
> +static inline int __libxl_device_model_start_timeout(void)
Could you rename that function? Probably:
libxl__device_model_start_timeout()
No leading '_', this is usually reserved, by glibc or C, I forgot the
details.
Also, internal libxl function have two '_', so full prefix is "libxl__".
> +{
> + const char *timeout_env = getenv("LIBXL_DEVICE_MODEL_START_TIMEOUT");
> + return timeout_env ? atoi(timeout_env)
That usage of atoi() isn't good, because on conversion error, 0 is
returned, which disable the timeout. I would rather fallback when we
don't have a number.
One case that might be more problematic than other might be:
LIBXL_DEVICE_MODEL_START_TIMEOUT= xl create
I think we would have a timeout of 0, instead of a fallback to the
default.
> + : LIBXL_DEVICE_MODEL_START_TIMEOUT;
> +}
> #define LIBXL_DEVICE_MODEL_SAVE_FILE XEN_LIB_DIR "/qemu-save" /* .$domid */
> #define LIBXL_DEVICE_MODEL_RESTORE_FILE XEN_LIB_DIR "/qemu-resume" /*
> .$domid */
> #define LIBXL_QMP_CMD_TIMEOUT 10
> diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
> index 96cb4da079..7bdd9f6c3b 100644
> --- a/tools/libs/light/libxl_pci.c
> +++ b/tools/libs/light/libxl_pci.c
> @@ -1157,7 +1157,7 @@ static void do_pci_add(libxl__egc *egc,
> pas->xswait.what = "Device Model";
> pas->xswait.path = DEVICE_MODEL_XS_PATH(gc,
> libxl_get_stubdom_id(CTX, domid), domid, "/state");
> - pas->xswait.timeout_ms = LIBXL_DEVICE_MODEL_START_TIMEOUT *
> 1000;
> + pas->xswait.timeout_ms =
> __libxl_device_model_start_timeout() * 1000;
That used by libxl__xswait_start(), and "0" seems to result in a
failure.
> pas->xswait.callback = pci_add_qemu_trad_watch_state_cb;
> rc = libxl__xswait_start(gc, &pas->xswait);
> if (rc) goto out;
> @@ -1719,7 +1719,7 @@ static void device_pci_add_stubdom_wait(libxl__egc *egc,
> rc = libxl__ev_devstate_wait(ao, &pas->pciback_ds,
> device_pci_add_stubdom_ready,
> state_path, XenbusStateConnected,
> - LIBXL_DEVICE_MODEL_START_TIMEOUT * 1000);
> + __libxl_device_model_start_timeout() * 1000);
That value will be use by libxl__xswait_start().
> if (rc) goto out;
> return;
> out:
> @@ -1976,7 +1976,7 @@ static void do_pci_remove(libxl__egc *egc,
> pci_remove_state *prs)
> prs->xswait.what = "Device Model";
> prs->xswait.path = DEVICE_MODEL_XS_PATH(gc,
> libxl_get_stubdom_id(CTX, domid), domid, "/state");
> - prs->xswait.timeout_ms = LIBXL_DEVICE_MODEL_START_TIMEOUT * 1000;
> + prs->xswait.timeout_ms = __libxl_device_model_start_timeout() *
> 1000;
That value will be use by libxl__xswait_start().
> prs->xswait.callback = pci_remove_qemu_trad_watch_state_cb;
> rc = libxl__xswait_start(gc, &prs->xswait);
> if (rc) goto out_fail;
So, overall, I'm fine with been able to change the timeout via env var,
but disabling the timeout might not be easy or possible, even if "-1"
might be an option, or -1000 in most case.
So, you change the man page to only allow value>0 ? And a timeout of 0
might be best to revert to the default.
Thanks,
--
Anthony PERARD
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