Date: Tue, 21 Feb 2006 10:40:17 -0800
From: "Paul E. McKenney" <paulmck@us.ibm.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] introduce sig_needs_tasklist() helper
Message-ID: <20060221184017.GD1295@us.ibm.com>
Reply-To: paulmck@us.ibm.com
References: <43F76374.EDA3ED9D@tv-sign.ru> <20060221021302.GR1480@us.ibm.com> <43FB5B15.F88FF5A8@tv-sign.ru>
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On Tue, Feb 21, 2006 at 09:25:25PM +0300, Oleg Nesterov wrote:
> "Paul E. McKenney" wrote:
> > 
> > On Sat, Feb 18, 2006 at 09:12:04PM +0300, Oleg Nesterov wrote:
> > > +#define sig_needs_tasklist(sig) \
> > > +             (((sig) < SIGRTMIN)  && T(sig, SIG_KERNEL_STOP_MASK | M(SIGCONT)))
> > > +
> > 
> > Seems to me to be an improvement, but why not also encapsulate the
> > lock acquisition, something like:
> > 
> >         static inline int sig_tasklist_lock(int sig)
> >         {
> >                 if (unlikely(sig_needs_tasklist(sig)) {
> >                         read_lock(&tasklist_lock);
> >                         return 1;
> >                 }
> >                 return 0;
> >         }
> > 
> >         static inline void sig_tasklist_unlock(int acquired_tasklist_lock)
> >         {
> >                 if (acquired_tasklist_lock)
> >                         read_unlock(&tasklist_lock);
> >         }
> 
> I hope we will have
> 
> 	#define sig_needs_tasklist(sig)	  (sig == SIGCONT)
> 
> really soon (I planned to submit the final bits today, but
> for some stupid reasons I can't do anything till weekend),
> so I think it's better to kill 'acquired_tasklist_lock' and
> just do:
> 
> 	void sig_tasklist_lock(sig)
> 	{
> 		if (sig_needs_tasklist(sig))
> 			read_lock(&tasklist_lock);
> 	}
> 
> 	void sig_tasklist_unlock(sig)
> 	{
> 		if (sig_needs_tasklist(sig));
> 			read_unlock(&tasklist_lock);
> 	}

Even better!

						Thanx, Paul
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