Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755263Ab2HaXqD (ORCPT ); Fri, 31 Aug 2012 19:46:03 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:33100 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755171Ab2HaXqA (ORCPT ); Fri, 31 Aug 2012 19:46:00 -0400 X-Originating-IP: 217.70.178.133 X-Originating-IP: 173.246.103.110 Date: Fri, 31 Aug 2012 16:45:51 -0700 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org, Alessio Igor Bogani , Avi Kivity , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , "H. Peter Anvin" , Ingo Molnar , Kevin Hilman , Max Krasnyansky , Stephen Hemminger , Sven-Thorsten Dietrich Subject: Re: [PATCH tip/core/rcu 05/26] rcu: Allow rcu_user_enter()/exit() to nest Message-ID: <20120831234550.GC11771@jtriplet-mobl1> References: <20120830210520.GA2824@linux.vnet.ibm.com> <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> <1346360743-3628-5-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1346360743-3628-5-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5462 Lines: 176 On Thu, Aug 30, 2012 at 02:05:22PM -0700, Paul E. McKenney wrote: > From: Frederic Weisbecker > > Allow calls to rcu_user_enter() even if we are already > in userspace (as seen by RCU) and allow calls to rcu_user_exit() > even if we are already in the kernel. > > This makes the APIs more flexible to be called from architectures. > Exception entries for example won't need to know if they come from > userspace before calling rcu_user_exit(). > > Signed-off-by: Frederic Weisbecker > Cc: Alessio Igor Bogani > Cc: Andrew Morton > Cc: Avi Kivity > Cc: Chris Metcalf > Cc: Christoph Lameter > Cc: Geoff Levand > Cc: Gilad Ben Yossef > Cc: Hakan Akkan > Cc: H. Peter Anvin > Cc: Ingo Molnar > Cc: Josh Triplett > Cc: Kevin Hilman > Cc: Max Krasnyansky > Cc: Peter Zijlstra > Cc: Stephen Hemminger > Cc: Steven Rostedt > Cc: Sven-Thorsten Dietrich > Cc: Thomas Gleixner > Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett > kernel/rcutree.c | 41 +++++++++++++++++++++++++++++++++-------- > kernel/rcutree.h | 3 +++ > 2 files changed, 36 insertions(+), 8 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index e287c4a..8bbc7fb 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -390,11 +390,9 @@ static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval, > */ > static void rcu_eqs_enter(bool user) > { > - unsigned long flags; > long long oldval; > struct rcu_dynticks *rdtp; > > - local_irq_save(flags); > rdtp = &__get_cpu_var(rcu_dynticks); > oldval = rdtp->dynticks_nesting; > WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); > @@ -403,7 +401,6 @@ static void rcu_eqs_enter(bool user) > else > rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; > rcu_eqs_enter_common(rdtp, oldval, user); > - local_irq_restore(flags); > } > > /** > @@ -420,7 +417,11 @@ static void rcu_eqs_enter(bool user) > */ > void rcu_idle_enter(void) > { > + unsigned long flags; > + > + local_irq_save(flags); > rcu_eqs_enter(0); > + local_irq_restore(flags); > } > EXPORT_SYMBOL_GPL(rcu_idle_enter); > > @@ -435,7 +436,18 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter); > */ > void rcu_user_enter(void) > { > - rcu_eqs_enter(1); > + unsigned long flags; > + struct rcu_dynticks *rdtp; > + > + WARN_ON_ONCE(!current->mm); > + > + local_irq_save(flags); > + rdtp = &__get_cpu_var(rcu_dynticks); > + if (!rdtp->in_user) { > + rdtp->in_user = true; > + rcu_eqs_enter(1); > + } > + local_irq_restore(flags); > } > EXPORT_SYMBOL_GPL(rcu_user_enter); > > @@ -530,11 +542,9 @@ static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval, > */ > static void rcu_eqs_exit(bool user) > { > - unsigned long flags; > struct rcu_dynticks *rdtp; > long long oldval; > > - local_irq_save(flags); > rdtp = &__get_cpu_var(rcu_dynticks); > oldval = rdtp->dynticks_nesting; > WARN_ON_ONCE(oldval < 0); > @@ -543,7 +553,6 @@ static void rcu_eqs_exit(bool user) > else > rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; > rcu_eqs_exit_common(rdtp, oldval, user); > - local_irq_restore(flags); > } > > /** > @@ -559,7 +568,11 @@ static void rcu_eqs_exit(bool user) > */ > void rcu_idle_exit(void) > { > + unsigned long flags; > + > + local_irq_save(flags); > rcu_eqs_exit(0); > + local_irq_restore(flags); > } > EXPORT_SYMBOL_GPL(rcu_idle_exit); > > @@ -572,7 +585,16 @@ EXPORT_SYMBOL_GPL(rcu_idle_exit); > */ > void rcu_user_exit(void) > { > - rcu_eqs_exit(1); > + unsigned long flags; > + struct rcu_dynticks *rdtp; > + > + local_irq_save(flags); > + rdtp = &__get_cpu_var(rcu_dynticks); > + if (rdtp->in_user) { > + rdtp->in_user = false; > + rcu_eqs_exit(1); > + } > + local_irq_restore(flags); > } > EXPORT_SYMBOL_GPL(rcu_user_exit); > > @@ -2590,6 +2612,9 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) > rdp->dynticks = &per_cpu(rcu_dynticks, cpu); > WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); > WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); > +#ifdef CONFIG_RCU_USER_QS > + WARN_ON_ONCE(rdp->dynticks->in_user); > +#endif > rdp->cpu = cpu; > rdp->rsp = rsp; > raw_spin_unlock_irqrestore(&rnp->lock, flags); > diff --git a/kernel/rcutree.h b/kernel/rcutree.h > index 4d29169..0dd5fd6 100644 > --- a/kernel/rcutree.h > +++ b/kernel/rcutree.h > @@ -102,6 +102,9 @@ struct rcu_dynticks { > /* idle-period nonlazy_posted snapshot. */ > int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ > #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ > +#ifdef CONFIG_RCU_USER_QS > + bool in_user; /* Is the CPU in userland from RCU POV? */ > +#endif > }; > > /* RCU's kthread states for tracing. */ > -- > 1.7.8 > -- 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/