Messages in this thread | | | Date | Mon, 9 Jul 2012 19:42:02 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 1/6] rcu: Settle config for userspace extended quiescent state |
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On Fri, Jul 06, 2012 at 09:31:29AM -0700, Paul E. McKenney wrote: > On Fri, Jul 06, 2012 at 02:00:13PM +0200, Frederic Weisbecker wrote: > > Create a new config option under the RCU menu that put > > CPUs under RCU extended quiescent state (as in dynticks > > idle mode) when they run in userspace. This require > > some contribution from architectures to hook into kernel > > and userspace boundaries. > > > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > > Cc: Alessio Igor Bogani <abogani@kernel.org> > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Avi Kivity <avi@redhat.com> > > Cc: Chris Metcalf <cmetcalf@tilera.com> > > Cc: Christoph Lameter <cl@linux.com> > > Cc: Geoff Levand <geoff@infradead.org> > > Cc: Gilad Ben Yossef <gilad@benyossef.com> > > Cc: Hakan Akkan <hakanakkan@gmail.com> > > Cc: H. Peter Anvin <hpa@zytor.com> > > Cc: Ingo Molnar <mingo@kernel.org> > > Cc: Josh Triplett <josh@joshtriplett.org> > > Cc: Kevin Hilman <khilman@ti.com> > > Cc: Max Krasnyansky <maxk@qualcomm.com> > > Cc: Peter Zijlstra <peterz@infradead.org> > > Cc: Stephen Hemminger <shemminger@vyatta.com> > > Cc: Steven Rostedt <rostedt@goodmis.org> > > Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com> > > Cc: Thomas Gleixner <tglx@linutronix.de> > > --- > > arch/Kconfig | 13 +++++++++++++ > > init/Kconfig | 10 ++++++++++ > > kernel/rcutree.c | 4 ++++ > > 3 files changed, 27 insertions(+), 0 deletions(-) > > > > diff --git a/arch/Kconfig b/arch/Kconfig > > index 8c3d957..c2e0ce4 100644 > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -274,4 +274,17 @@ config SECCOMP_FILTER > > > > See Documentation/prctl/seccomp_filter.txt for details. > > > > +config HAVE_RCU_USER_QS > > + bool > > + help > > + Provide kernel entry/exit hooks necessary for userspace > > + RCU extended quiescent state. Syscalls and exceptions > > + low level handlers must be wrapped with a call to rcu_user_exit() > > + on entry and rcu_user_enter() before resuming userspace. Irqs > > + entry don't need to call rcu_user_exit() because their high level > > + handlers are protected inside rcu_irq_enter/rcu_irq_exit() but > > + preemption or signal handling on irq exit still need to be protected > > + with a call to rcu_user_exit(). rcu_user_enter() must then be > > + called back on irq exit when the preempted task is back on the CPU. > > + > > source "kernel/gcov/Kconfig" > > diff --git a/init/Kconfig b/init/Kconfig > > index d07dcf9..3a4af8f 100644 > > --- a/init/Kconfig > > +++ b/init/Kconfig > > @@ -441,6 +441,16 @@ config PREEMPT_RCU > > This option enables preemptible-RCU code that is common between > > the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. > > > > +config RCU_USER_QS > > + bool "Consider userspace as in RCU extended quiescent state" > > + depends on HAVE_RCU_USER_QS && SMP > > OK, I'll bite... Why the "SMP"? RCU could make good use of knowing > about user-mode executing even in UP kernels.
Because Tiny RCU doesn't implement rcu_user_enter()/exit yet. And it doesn't need it for now.
To better express the constraint I should probably have used:
depends on TREE_RCU || TREE_PREEMPT_RCU
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