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Re: Cygwin 1.7: Concurrency Issue with Shared State Initialization
On Wed, Mar 10, 2010 at 10:59:29AM +0100, Corinna Vinschen wrote:
>On Mar 10 10:55, Schmidt, Oliver wrote:
>> Hi Corrina,
>>
>> Thanks for your involvement :-)
>>
>> >> [...] a spinlock [...] With
>> >> InterlockedCompareExchange() and Sleep() it should be quite simple to
>> >> create one that's very efficient in the usual scenario.
>>
>> > Does the below patch fix this for you?
>>
>> I'll test the snapshot asap!
>>
>> [...]
>> + LONG init = InterlockedCompareExchange (&installation_root_init, 1L, 0L);
>> [...]
>> + low_priority_sleep (0);
>> [...]
>>
>> I see we were thinking along the same lines ;-)
>
>The final patch is from cgf. It's probably more performant since it
>drops the requirement for an additional spinlock.
The snapshot contains try #3 on getting the locking right. I had to scrap
my approach after Corinna politely reminded me that I had done something
stupid in the prior snapshot.
But, the spinlock approach was nothing new. We use that technique in
several places in Cygwin.
cgf
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