Re: [patch v2] epoll use a single inode ...

[Davide Libenzi]

On Tue, 6 Mar 2007, Eric Dumazet wrote:

> Davide Libenzi a écrit :
> > On Mon, 5 Mar 2007, H. Peter Anvin wrote:
> > 
> > > Davide Libenzi wrote:
> > > > Right now is using:
> > > > 
> > > > 	this.len = sprintf(name, "[%u.%d]", current->pid, fd);
> > > > 
> > > > That should be unique and not have the wraparound problem. Ack?
> > > > 
> > > NAK, very much NAK.
> > > 
> > > File descriptors aren't file structures, they're *pointers* to file
> > > structures.
> > > 
> > > It's perfectly possible -- downright common -- for a file descriptor to be
> > > inherited by another process, and then the pid is recycled -- collision.
> > 
> > Ugh! Right! 64 bit counter it is ... :)
> 
> For epoll, I suspect this is harmless : Programs dont allocate epolls fd every
> milli second, but at startup only.
> 
> For pipes/sockets, using a 64 bits would be problematic, because sprintf()
> uses a divide for each digit. And a divide is slow. Ten divides are *very*
> slow.

This would be used for epoll, signalfd and timerfd. And the printf format 
is %llu ;)



- Davide