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SubjectRe: PROBLEM: pthread-safety bug in write(2) on Linux 2.6.x


On Thu, 13 Apr 2006, Linus Torvalds wrote:

>
>
> On Fri, 14 Apr 2006, Alan Cox wrote:
> >
> > Quality for whom ? There is a measurable cost to all that extra locking
> > which will hurt everyone. Given existing kernels don't make the
> > guarantee and SuS v3 does not make the guarantee the apps that need it
> > will continue to do the extra work themselves anyway.
>
> True.

Side note: if you want the strange POSIX guarantees that Dan quoted
(atomicity between write and fstat), you'd almost have to do it with
user-space crapola magic locks. Doing it in the kernel would just be
insane, you'd have to have some per-process "IO semaphore".

(Doing it in user space _also_ sounds insane, but then you could have a
switch like "POSIX me harder, and do all the really stupid things" at
compile time or something)

Linus
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