On Fri, Apr 17, 2015 at 10:41:30AM -0400, Steven Rostedt wrote: > On Fri, 17 Apr 2015 16:38:04 +0200 > Milos Vyletel <milos@xxxxxxxxxx> wrote: > > > Make a note stating that repeated calls of rcu_dereference() may not > > return the same pointer if update happens while in critical section. > > > > Reported-by: Jeff Haran <jeff.haran@xxxxxxxxxx> > > Signed-off-by: Milos Vyletel <milos@xxxxxxxxxx> > > Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Queued for 4.2, thank you both! Thanx, Paul > -- Steve > > > --- > > Documentation/RCU/whatisRCU.txt | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt > > index 88dfce1..16622c9 100644 > > --- a/Documentation/RCU/whatisRCU.txt > > +++ b/Documentation/RCU/whatisRCU.txt > > @@ -256,7 +256,9 @@ rcu_dereference() > > If you are going to be fetching multiple fields from the > > RCU-protected structure, using the local variable is of > > course preferred. Repeated rcu_dereference() calls look > > - ugly and incur unnecessary overhead on Alpha CPUs. > > + ugly, do not guarantee that the same pointer will be returned > > + if an update happened while in the critical section, and incur > > + unnecessary overhead on Alpha CPUs. > > > > Note that the value returned by rcu_dereference() is valid > > only within the enclosing RCU read-side critical section. > -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
