RE: [PATCH 1/1] staging: hv: Fix race condition on IC channelinitialization

From: Haiyang Zhang
Date: Fri May 21 2010 - 18:07:29 EST

> From: Greg KH [mailto:gregkh@xxxxxxx]
> > +/* Counter of IC channels initialized */
> > +atomic_t hv_utils_initcnt = ATOMIC_INIT(0);
> This doesn't need to be an atomic variable, does it really?
> Why not have a simple bool variable "vmbus_initialized" or something.
> It starts out as false, and then turns true when you are up and ready.
> Then provide a function that tests it:
> bool hv_vmbus_ready(void)
> {
> return vmbus_initialized
> }
> EXPORT_SYMBOL_GPL(hv_vmbus_ready);
> this turns into a simple function call, again, never needing to know
> about message types or any other mess.

This looks good. I will add the hv_vmbus_ready() function. It doesn't even
have to be exported symbol, because it's only used in vmbus module to ensure
all channels are ready before vmbus_init() returns. Other modules won't get a
chance to see uninitialized channels after hv_vmbus is loaded.

Also, I'll cleanup the printk in hv_utils load/unload.

Regarding the atomic variable -- the channel offer processing function is
triggered by interrupts from host -- should we be concerned about "counter++"
racing with each other in two interrupts happening around the same time?


- Haiyang

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