[lkml]   [2002]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC] New locking primitive for 2.5
On Fri, Feb 08, 2002 at 03:04:34PM -0500, Jeff Garzik wrote:
> Linus Torvalds wrote:
> >
> > On Fri, 8 Feb 2002, Ingo Molnar wrote:
> > >
> > > and regarding the reintroduction of BKL, *please* do not just use a global
> > > locks around such pieces of code, lock bouncing sucks on SMP, even if
> > > there is no overhead.
> >
> > I'd suggest not having a lock at all, but instead add two functions: one
> > to read a 64-bit value atomically, the other to write it atomically (and
> > they'd be atomic only wrt each other, no memory barriers etc implied).
> >
> > On 64-bit architectures that's just a direct dereference, and even on x86
> > it's just a "cmpxchg8b".
> Are there architectures out there that absolutely must implement this
> with a spinlock? Your suggested API of functions to read/write 64-bit
> values atomically would work for such a case, but still I am just
> curious.

SMP 486s would need that (if there is such a beast). What point does x86
get the 64 bit instructions? If after 586, then it would definately need a
spinlock or somesuch in those functions.

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: 2005-03-22 13:24    [W:0.112 / U:5.096 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site