Re: Multithread select() bug

[Andre Ben Hamou <andre@bluetheta.com>]

Eric Dumazet wrote:
> So please how do you guarantee that thread 1 runs *before* thread 2)
> 
> Thread 1)
>        select( fd)
> 
> Thread 2)
>        close(fd)
> 
> Thats not possible.
> 

I see where you're coming from, in that there is a potential race 
condition as to the socket being connected as I reach the select call.

This is an important concern but it is, I think, orthogonal to the 
original problem as there are two possible socket states at the point at 
which select gets called (as far as I can see)...

1. The socket is in its connected state
2. The socket has already been closed by the parent thread

As I understand it, if 1 is true (which corresponds to my original 
post), then select should return the moment the socket gets closed and, 
if 2 is true (which I believe corresponds to your concern), then select 
should return immediately anyway as the socket would not block if read from.

Sorry to be a pest, but I'm trying to get this clear in my head. Is it 
possible I've over-estimated the thread-safety of the select and close 
calls?

Cheers,

Andre Ben Hamou
Imperial College London

-- 

...and, on the seventh day, God switched off his Mac.