[lkml]   [2006]   [Jul]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] Use uname not sysctl to get the kernel revision
On Thu, 2006-07-13 at 00:07 +0100, Alan Cox wrote:
> Ar Mer, 2006-07-12 am 16:26 -0600, ysgrifennodd Eric W. Biederman:
> > If the lock is not short lived then the release is like to be a long
> > ways off. If the lock is not highly contended then you are not likely
> > to hit the window when someone else as the contended lock.
> >
> > How frequent are highly contended short lived locks in user space?
> I'm not sure it matters.
> If you want to do the job right then do this
> - Stick an indicator of how much else wants to run on this CPU in the
> vsyscall page or similar location

Except that "this cpu" doesn't really mean anything in userspace, and
while I think Andi has some tricks to get some sort of CPU number to
userspace (though it's really only valid during the execution of the
instruction that reads it :) I haven't yet found an equivalent for
powerpc (and possibly other architectures will have the same problem).

> In your locks you can now do
> while(try_and_grab_lock() == FAILED) {
> if (kernelpage->waiting > 0)
> sys_somelockwaitthing()
> }
> Furthermore the kernel can be intelligent about the waiting indicator
> for power or other global scheduling reasons
> [Disclaimer: There is a patent issue around this technique but its not
> one that will impact GPL code as permissions are given for GPL use.]
> Alan

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2006-07-14 20:51    [W:0.087 / U:3.372 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site