Re: [PATCH v3 11/29] media: iris: implement reqbuf ioctl with vb2_queue_setup

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On 06/09/2024 13:50, Bryan O'Donoghue wrote:
+
+        ret = core->hfi_ops->session_open(inst);
+        if (ret) {
+            ret = -EINVAL;
+            dev_err(core->dev, "session open failed\n");
+            goto unlock;
+        }

I don't understand the lifetime of the core->lock mutex here.

It has verified the state as !ISIR_CORE_ERROR and then _released_ the lock so by the time you get to core->hfi_ops->session_open() you've not guaranteed the state at all.

Shouldn't you continue to hold the core mutex for the duration of the core->does_stuff() operation ?

i.e. the state was not !IRIS_CORE_ERROR at an indeterminate time prior to the next use of core-> ...

Perhaps this is all very obvious but, I'm not immediately understanding what the mutex gurantees nor for how long it does that.

You'd probably be better off

- taking the mutex at the external facing API
- validating state if you must
- doing all of your core ops
- dropping

If I'm interpreting your code right, there's alot of checking state in function a -> lock/check/unlock with function a then calling function b - which again verifies core->state and then optionally modifies say the linked list.

But since function b is called by function a, and function b requires the core->lock - you may as well have held that lock from a through b.

Moreover - what's the use case of the very granular core->stat lock checking ?

When is it valid for example for iris_vb2_queue_setup() to have core->state change state during the lifetime of iris_vb2_queue_setup() ?

iris_vb2_queue_setup() checks core->state
	-> locks - checks - release
		-> calls iris_hfi_gen1_session_open or
		         iris_hfi_gen2_session_open
			-> what is the assumed core->state @ that point?

So that's what I mean, I'm not immediately understanding why this granular locking scheme is in use, seems way, way, way too granular ?

---
bod




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