>>> On 5/21/2010 at 4:55 PM, in message <20100521205527.GB9594@xxxxxxx>, Greg KH
<gregkh@xxxxxxx> wrote:
> On Fri, May 21, 2010 at 02:21:46PM -0600, Ky Srinivasan wrote:
>>
>>
>> >>> On 5/21/2010 at 4:12 PM, in message <20100521201228.GA6712@xxxxxxx>, Greg KH
>> <gregkh@xxxxxxx> wrote:
>> > On Fri, May 21, 2010 at 07:58:26PM +0000, Haiyang Zhang wrote:
>> >> From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
>> >>
>> >> Subject: staging: hv: Fix race condition on IC channel initialization
>> >> There is a possible race condition when hv_utils starts to load immediately
>> >> after hv_vmbus is loading - null pointer error could happen.
>> >> This patch added an atomic counter to ensure all channels are ready before
>> >> vmbus_init() returns. So another module won't have any uninitialized
>> > channel.
>> >
>> > Better, but not quite ready...
>> >
>> >> +/* 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);
>> I agree with Greg; I would go a step further and deal with this issue
>> as part of loading the bus driver. After all, we already have
>> dependencies established for various LIC drivers on the bus driver.
>> The fact that even after the bus driver is loaded we cannot reliably
>> load other drivers implies that there is an additional dependency that
>> is not currently being handled. Why can't we ensure that the bus
>> driver is fully initialized before we are done with loading the bus
>> driver.
>
> Um, I think that is what this patch fixes :)
>
> It just doesn't do it in a way that I think is very good...
Ok, my mistake. When I saw hv_vmbus_ready function being exported, I was under the impression each of the drivers that depend on the bus driver to check if the bus driver was properly initialized.
Regards,
K. Y
>
> thanks,
>
> greg k-h
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