Re: [igt-dev] [PATCH v7 1/2] tests: Add a new test for driver/device hot reload

[Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>]

Hi Kasia,

On Friday, April 12, 2019 10:16:41 AM CEST Katarzyna Dec wrote:
> On Thu, Apr 11, 2019 at 02:26:28PM +0200, Janusz Krzysztofik wrote:
> > From: Janusz Krzysztofik <janusz.krzysztofik@intel.com>
> > 
> > Run a dummy load in background to put some workload on a device, then try
> > to either remove (unplug) the device from its bus, or unbind the device's
> > driver from it, depending on which subtest has been selected.  If
> > succeeded, unload the driver, rescan the device's bus if needed and
> > perform health checks on the device with the driver reloaded.
> > 
> > The dummy load is run from igt_fixture and in a sub-process, not directly
> > from subtests,  as it is expected to fail and it's more simple to ignore
> > igt_abort() in a sub-process.  Moreover, as soon as the sub-process fails
> > and exits, resources it was using are freed automatically so there is no
> > need to do any cleanups required for smooth module unload from the test
> > level itself.  Those cleanups might also make the subtests fail if simply
> > 
> > using igt library functions for that instead of reimplementing their safe
> > parts only.
> > 
> > The driver hot unbind / device hot unplug operation is expected to succeed
> > and the background workload sub-process to die in a reasonable time,
> > however long timeouts are used to let kernel level timeouts pop up first
> > if hit by a bug.
> > 
> > The dummy load works only on i915 driver.  The test is skipped on other
> > hardware unless they provide their implementation of igt_spin_batch_new()
> > and friends.
> 
> There are few not needed spaces above, no need to send new version if this
> will be the only thing (can be fixed during merging).

OK.

> > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@intel.com>
> > ---
> > 
> >  tests/Makefile.sources  |   1 +
> >  tests/core_hot_reload.c | 256 ++++++++++++++++++++++++++++++++++++++++
> >  tests/meson.build       |   1 +
> >  3 files changed, 258 insertions(+)
> >  create mode 100644 tests/core_hot_reload.c
> > 
> > diff --git a/tests/Makefile.sources b/tests/Makefile.sources
> > index 214698da..d2c0941d 100644
> > --- a/tests/Makefile.sources
> > +++ b/tests/Makefile.sources
> > @@ -16,6 +16,7 @@ TESTS_progs = \
> > 
> >  	core_getclient \
> >  	core_getstats \
> >  	core_getversion \
> > 
> > +	core_hot_reload \
> > 
> >  	core_setmaster_vs_auth \
> >  	debugfs_test \
> >  	drm_import_export \
> > 
> > diff --git a/tests/core_hot_reload.c b/tests/core_hot_reload.c
> > new file mode 100644
> > index 00000000..d862c99c
> > --- /dev/null
> > +++ b/tests/core_hot_reload.c
> > @@ -0,0 +1,256 @@
> > +/*
> > + * Copyright © 2019 Intel Corporation
> > + *
> > + * Permission is hereby granted, free of charge, to any person obtaining
> > a
> > + * copy of this software and associated documentation files (the
> > "Software"), + * to deal in the Software without restriction, including
> > without limitation + * the rights to use, copy, modify, merge, publish,
> > distribute, sublicense, + * and/or sell copies of the Software, and to
> > permit persons to whom the + * Software is furnished to do so, subject to
> > the following conditions: + *
> > + * The above copyright notice and this permission notice (including the
> > next + * paragraph) shall be included in all copies or substantial
> > portions of the + * Software.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> > EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> > MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND
> > NONINFRINGEMENT.  IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS
> > BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN
> > ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN
> > CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE
> > SOFTWARE.
> > + */
> > +
> > +#include "igt.h"
> > +#include "igt_device.h"
> > +#include "igt_dummyload.h"
> > +#include "igt_kmod.h"
> > +#include "igt_sysfs.h"
> > +
> > +#include <getopt.h>
> > +#include <limits.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +
> > +
> 
> I think that 1 blank line will be fine.

OK.

> > +typedef int (*action_t)(int dir);
> > +typedef void (*workload_wait_t)(void *priv);
> > +typedef void (*workload_t)(int device, const void *priv);
> > +
> > +
> 
> same here :)

OK.

> > +/*
> > + * Actions
> > + *
> > + * Purpose: make the device disappear
> > + *
> > + * @dir: file descriptor of an open device sysfs directory
> > + *
> > + * Return value: file descriptor of an open device bus' sysfs directory
> > + * 		 or -1 if no bus rescan is needed
> > + */
> > +
> 
> I went though your answers on my quesions. It is more then ok to have a
> wider overview on what is going on in whole binary, although I would prefer
> to have some summary doc at the begining and small docs aboe functions (if
> needed).

Let's try to agree on that before I submit another version.

There are now 3 multiline comments, each of them open one of three sections of 
the code:
1) a section with different action functions,
2) a section with different workload functions,
3) a section with common code, I called it skeleton.

If I move all those three comments at the top, they will loose their purpose 
of opening the sections.  That's why I propose to keep them where they are 
now, and to add another comment at the top.  Here is how it may look like:

 /**
 * This binary includes subtests for performing the following two actions:
 * - unbinding the driver from a device under load,
 * - virtually unplugging the device under load from its bus.
 * Both actions are implemented as separate functions sharing the same API,
 * wrapped with a common skeleton.  A similar approach has been taken for
 * defining different workloads.  Even if only one type of workload is currently
 * implemented, the code is ready for extending it with other workloads defined
 * as additional workload functions which follow the same API.
 * Since the unplug action actually removes the device instance from the system,
 * a bus rescan operation is needed to reinstantiate the device after completion
 * of the test.  For that purpose, the action passes back a file descriptor of
 * an open sysfs directory representing the bus on which the rescan is then 
 * performed.  In case of the unbind action, it always returns an invalid file
 * descriptor to inform the skeleton that no bus rescan is needed.
 * Since a workload is expected to crash as a result of an action, its
 * invocation is performed from a helper process run from the igt_fixture block
 * in order to avoid direct influence of that crash on a test result.
 */

What do you think?

> > +/* Unbind the driver from the device */
> > +static int driver_unbind(int dir)
> > +{
> > +	char path[PATH_MAX], *dev_bus_addr;
> > +	int len;
> > +
> > +	len = readlinkat(dir, "device", path, sizeof(path) - 1);
> > +	path[len] = '\0';
> > +	dev_bus_addr = strrchr(path, '/') + 1;
> > +
> > +	igt_set_timeout(60, "Driver unbind timeout!");
> > +	igt_sysfs_set(dir, "device/driver/unbind", dev_bus_addr);
> > +
> > +	/* No need for bus rescan */
> > +	return -1;
> > +}
> > +
> > +/* Remove (virtually unplug) the device from its bus */
> > +static int device_unplug(int dir)
> > +{
> > +	int bus;
> > +
> > +	bus = openat(dir, "device/subsystem", O_DIRECTORY);
> > +	igt_assert(bus >= 0);
> > +
> > +	igt_set_timeout(60, "Device unplug timeout!");
> > +	igt_sysfs_set(dir, "device/remove", "1");
> > +
> > +	return bus;
> > +}
> > +
> > +
> > +/*
> > + * Workloads
> > + *
> > + * Purpose: Put some long lasting load on the device
> > + *
> > + * @device: open device file descriptor,
> > + * @priv: pointer to an optional argument passed to the workload
> > + *
> > + * Return value: none
> > + */
> > +
> > +/* Workload using igt_spin_batch_run() */
> > +
> > +static void spin_batch(int device, const void *priv)
> > +{
> > +	igt_spin_t *spin;
> > +
> > +	/* submit the job */
> > +	spin = igt_spin_batch_new(device);
> > +
> > +	/* wait for the job to crash */
> > +	gem_sync(device, spin->handle);
> > +
> > +	/* clean up if still possible */
> > +	igt_spin_batch_free(device, spin);
> > +}
> > +
> > +
> > +/*
> > + * Skeleton
> > + */
> > +
> > +static void healthcheck(int chipset)
> > +{
> > +	if (chipset == DRIVER_INTEL) {
> > +		/*
> > +		 * We have it perfectly implemented in i915_module_load,
> > +		 * just use it.
> > +		 */
> > +		igt_assert(igt_system_quiet("i915_module_load --run-subtest reload")
> > +			   == IGT_EXIT_SUCCESS);
> > +	} else {
> > +		/*
> > +		 * We don't know how to check an unidentified device for health,
> > +		 * device reopen must suffice.
> > +		 */
> > +	}
> 
> I saw you answer about this else and I agree that it is not for us to decide
> what should code for other vendors look like. That is why we do not need
> else here at all

OK.

Janusz

> - healthcheck will be run only for INTEL + person who runs
> code will not see any message that 'if' here was not hit.
> 
> The rest looks fine.
> Kasia :)




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