[Openais] [PATCH] change fork() override to pthread_atfork() callbacks.

[Angus Salkeld]

On Tue, 2010-03-09 at 12:45 -0700, Steven Dake wrote:
> On Tue, 2010-03-09 at 07:07 +1100, Angus Salkeld wrote:
> > On VM (one cpu) I was getting very high cpu usage by corosync.
> > 
> > This was because of the tsafe code I added. This patch changes
> > the overriding of fork() to using pthread_atfork() callbacks
> > instead. It seems that during the fork the mutex was been held
> > so the child had a "taken" mutex.
> > 
> > -Angus
> > 
> One nitpicky spacing issue otherwise good for merge
> 

Committed as revision 2677.

-A

> > Signed-off-by: Angus Salkeld <asalkeld at redhat.com>
> > ---
> >  exec/tsafe.c |   44 ++++++++++++++++++++++++--------------------
> >  1 files changed, 24 insertions(+), 20 deletions(-)
> > 
> > diff --git a/exec/tsafe.c b/exec/tsafe.c
> > index aecfb15..e2b4f21 100644
> > --- a/exec/tsafe.c
> > +++ b/exec/tsafe.c
> > @@ -80,6 +80,9 @@
> >  static int tsafe_disabled = 1;
> >  static int tsafe_inited = 0;
> >  static char **coro_environ;
> > +static void atfork_prepare (void);
> > +static void atfork_parent (void);
> > +static void atfork_child (void);
> >  
> >  #if defined(HAVE_PTHREAD_SPIN_LOCK)
> >  static pthread_spinlock_t tsafe_enabled_mutex;
> > @@ -105,11 +108,13 @@ void tsafe_init (char **envp)
> >  #if defined(HAVE_PTHREAD_SPIN_LOCK)
> >         pthread_spin_init (&tsafe_enabled_mutex, 0);
> >  #endif
> > +
> > +       pthread_atfork (atfork_prepare, atfork_parent,atfork_child);
> > +
> 
> missing a space after ,atfork_child
> 
> >         tsafe_disabled = 1;
> >         tsafe_inited = 1;
> >  }
> >  
> > -
> >  static void tsafe_lock (void)
> >  {
> >  #if defined(HAVE_PTHREAD_SPIN_LOCK)
> > @@ -118,6 +123,7 @@ static void tsafe_lock (void)
> >         pthread_mutex_lock (&tsafe_enabled_mutex);
> >  #endif
> >  }
> > +
> >  static void tsafe_unlock (void)
> >  {
> >  #if defined(HAVE_PTHREAD_SPIN_LOCK)
> > @@ -141,6 +147,23 @@ void tsafe_on (void)
> >         tsafe_unlock ();
> >  }
> >  
> > +static void atfork_prepare (void)
> > +{
> > +       tsafe_lock ();
> > +}
> > +
> > +static void atfork_parent (void)
> > +{
> > +       tsafe_unlock ();
> > +}
> > +
> > +static void atfork_child (void)
> > +{
> > +       if (tsafe_inited && !tsafe_disabled) {
> > +               tsafe_disabled = 1;
> > +       }
> > +       tsafe_unlock ();
> > +}
> >  
> >  static void* _get_real_func_(const char * func_name)
> >  {
> > @@ -182,25 +205,6 @@ int pthread_create(pthread_t *thread, const
> > pthread_attr_t *attr,
> >         return real_pthread_create (thread, attr, start_routine, arg);
> >  }
> >  
> > -pid_t fork(void)
> > -{
> > -       static pid_t (*real_fork)(void) = NULL;
> > -       pid_t ret;
> > -
> > -       if (tsafe_inited && !tsafe_disabled) {
> > -               tsafe_off ();
> > -       }
> > -
> > -       if (real_fork == NULL) {
> > -               real_fork = _get_real_func_ ("fork");
> > -       }
> > -       ret = real_fork ();
> > -       if (ret == 0) {
> > -               /* if we have forked corosync then anything goes. */
> > -               tsafe_off ();
> > -       }
> > -       return ret;
> > -}
> >  #endif /* COROSYNC_LINUX */
> >  
> >  /*
> > -- 
> > 1.6.6.1
> > 
>