lkml.org 
[lkml]   [2005]   [Dec]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Fix RCU race in access of nohz_cpu_mask
Srivatsa Vaddagiri wrote:
>
> On Fri, Dec 09, 2005 at 10:17:38PM +0300, Oleg Nesterov wrote:
> > > rcp->cur++; /* New GP */
> > >
> > > smp_mb();
> >
> > I think I need some education on memory barriers.
> >
> > Does this mb() garantees that the new value of ->cur will be visible
> > on other cpus immediately after smp_mb() (so that rcu_pending() will
> > notice it) ?
>
> AFAIK the new value of ->cur should be visible to other CPUs when smp_mb()
> returns. Here's a definition of smp_mb() from Paul's article:
>
> smp_mb(): "memory barrier" that orders both loads and stores. This means loads
> and stores preceding the memory barrier are committed to memory before any
> loads and stores following the memory barrier.

Thanks, but this definition talks about ordering, it does not say
anything about the time when stores are really commited to memory
(and does it mean also that cache-lines are invalidated on other
cpus ?).

> [ http://www.linuxjournal.com/article/8211 ]

And thanks for this link, now I have some understanding about
read_barrier_depends() ...

Oleg.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-12-10 18:49    [W:0.198 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site