[ltt-dev] [rp] [PATCH RFC urcu 1/2] Provide pthread_atfork-friendly interfaces

[paulmck@linux.vnet.ibm.com (Paul E. McKenney)]

On Fri, Apr 01, 2011 at 04:52:50PM -0400, Mathieu Desnoyers wrote:
> * Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote:
> > Provides call_rcu_before_fork() and call_rcu_after_fork_parent() to
> > go with the existing call_rcu_after_fork_child().
> > 
> > Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
> > ---
> >  README          |    4 ++++
> >  urcu-call-rcu.c |   29 ++++++++++++++++++++++++++++-
> >  2 files changed, 32 insertions(+), 1 deletions(-)
> > 
> > diff --git a/README b/README
> > index f7f0dec..56e98d7 100644
> > --- a/README
> > +++ b/README
> > @@ -204,3 +204,7 @@ Interaction with fork()
> >  	liburcu-bp, which is designed to handle fork() by calling
> >  	rcu_bp_before_fork, rcu_bp_after_fork_parent and
> >  	rcu_bp_after_fork_child.
> > +
> > +	Applications that use call_rcu() are required to invoke
> > +	call_rcu_after_fork_child() from the child process after a
> > +	successful fork() system call that is not followed by exec().
> 
> Should you say something about the before hook, and after hook in the
> parent too ?

Good point, fixed as follows:

diff --git a/README b/README
index 56e98d7..3e23120 100644
--- a/README
+++ b/README
@@ -205,6 +205,8 @@ Interaction with fork()
 	rcu_bp_before_fork, rcu_bp_after_fork_parent and
 	rcu_bp_after_fork_child.
 
-	Applications that use call_rcu() are required to invoke
-	call_rcu_after_fork_child() from the child process after a
-	successful fork() system call that is not followed by exec().
+	Applications that use call_rcu() and that fork() without
+	doing an immediate exec() must take special action.  The parent
+	must invoke call_rcu_before_fork() before the fork() and
+	call_rcu_after_fork_parent() after the fork().  The child
+	process must invoke call_rcu_after_fork_child().