On 7/15/2020 5:42 PM, Jason Wang wrote:

On 2020/7/15 下午5:20, Zhu, Lingshan wrote:

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I meant something like:

unregister();
vq->call_ctx.producer.token = ctx;
register();

This is what we are doing now, or I must missed somethig:
if (ctx && ctx != token) {
    irq_bypass_unregister_producer(&vq->call_ctx.producer);
    vq->call_ctx.producer.token = ctx;
    irq_bypass_register_producer(&vq->call_ctx.producer);

}

It just unregister and register.

I meant there's probably no need for the check and another check and 
unregister before. The whole function is as simple as I suggested 
above.

Thanks

IMHO we still need the checks, this function handles three cases:
(1)if the ctx == token, we do nothing. For this unregister and 
register can work, but waste of time.

But we have a more simple code and we don't care about the performance 
here since the operations is rare.

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(2)if token exists but ctx is NULL, this means user space issued an 
unbind, so we need to only unregister the producer.

Note that the register/unregister have a graceful check of whether or 
not there's a token.

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(3)if ctx exists and ctx!=token, this means there is a new ctx, we 
need to update producer by unregister and register.

I think we can not simply handle all these cases by "unregister and 
register".

So it looks to me the functions are equivalent.

Thanks

Sounds reasonable, thanks!

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Thanks,
BR
Zhu Lingshan