Re: [PATCH, v3] shmat: introduce flag SHM_MAP_NOT_FIXED

[Andi Kleen]

On Wed, Oct 08, 2008 at 11:20:37AM +0100, Alan Cox wrote:
> > That is racy when multi threaded because shmat() doesn't replace, so you 
> > would need to munmap() inbetween and someone else could steal the area
> > then. Yes you could stick a loop around it. It could livelock.
> > No, it's not a good interface I would advocate.
> 
> You could just use pthread mutexes in your application. The rôle of the

malloc() can call mmap, so that would require putting a mutex around
each malloc(). Good luck finding them all.

> kernel is not to provide nappies for people who think programming is too
> hard but to provide services that can be used to build applications.

Outsourcing kernel locking to user space is not the way to go.

-Andi

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