Re: [PATCH v5] perf: arm_cspmu: Separate Arm and vendor module

On 2023-08-19 21:11, Besar Wicaksono wrote:
[...]

quoted

quoted

+void arm_cspmu_impl_unregister(const struct arm_cspmu_impl_match

*impl_match)

quoted

+{
+     struct device *dev;
+     struct arm_cspmu_impl_match *match;
+
+     match = arm_cspmu_impl_match_get(impl_match->pmiidr_val);
+
+     WARN_ON(!match);

Nit: do "if (WARN_ON(!match)) return;" rather than indenting almost the 
whole function.

quoted

quoted

+
+     if (match) {
+             /* Unbind the driver from all matching backend devices. */
+dev_release:
+             dev = driver_find_device(&arm_cspmu_driver.driver, NULL,
+                     match, arm_cspmu_match_device);
+             if (dev) {
+                     device_release_driver(dev);
+                     goto dev_release;
+             }

minor nit: We could simply do :

static int arm_cspmu_release_driver(struct device *dev, void *data)
{
         struct arm_cspmu *cspmu =
platform_get_drvdata(to_platform_device(dev));

         if (cspmu && cspmu->impl.match == match)
                 device_release_driver(dev);
         return 0;
}

                 ret = driver_for_each_device(&driver, NULL, match,
arm_csmpu_release_driver);

It doesn’t seem to work for me.
Is it safe to release while iterating via driver_for_each_device ?

Looking at the klist code it doesn't *obviously* appear safe to modify 
the list during iteration, so probably best not to risk it anyway. 
However, please try to write this loop as an actual loop, e.g.:

	while ((dev = driver_find_device()))
		device_release_driver();

At first glance I thought there was a bug here that it's only processing 
a single device, then eventually I saw the goto and my thought changed 
to "Eww..."

Thanks,
Robin.

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