Re: horrible disk thorughput on itanium

[Linus Torvalds]

On Fri, 7 Dec 2001, Andi Kleen wrote:
>
> Your proposals sound rather dangerous. They would silently break recompiled
> threaded programs that need the locking and don't use -D__REENTRANT

No it wouldn't.

Once you do a pthread_create(), the locking is there.

Before you do a pthread_create(), it doesn't lock.

What's the problem? Before you do a pthread_create(), you don't _NEED_
locking, because there is only one thread that accesses the stdio data
structures.

And there are no races - if there is only one thread, then another thread
couldn't be suddenly doing a pthread_create() during a stdio operations.

Safe, and efficient. Yes, it adds a flag test or a indirect branch, but
considering that you avoid a serialized locking instruction, the
optimization sounds obvious.

		Linus