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 <[email protected]> Cc: Alessio Igor Bogani <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Avi Kivity <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Geoff Levand <[email protected]> Cc: Gilad Ben Yossef <[email protected]> Cc: Hakan Akkan <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Josh Triplett <[email protected]> Cc: Kevin Hilman <[email protected]> Cc: Max Krasnyansky <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Stephen Hemminger <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Sven-Thorsten Dietrich <[email protected]> Cc: Thomas Gleixner <[email protected]> --- arch/Kconfig | 10 ++++++++++ include/linux/rcupdate.h | 8 ++++++++ init/Kconfig | 10 ++++++++++ kernel/rcutree.c | 5 ++++- 4 files changed, 32 insertions(+), 1 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 8c3d957..1c7c9be 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -274,4 +274,14 @@ 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 need to be wrapped inside + rcu_user_exit()-rcu_user_enter() through the slow path using + TIF_NOHZ flag. Exceptions handlers must be wrapped as well. Irqs + are already protected inside rcu_irq_enter/rcu_irq_exit() but + preemption or signal handling on irq exit still need to be protected. + source "kernel/gcov/Kconfig" diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 148f381..a72f25e 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -192,10 +192,18 @@ extern void rcu_idle_enter(void); extern void rcu_idle_exit(void); extern void rcu_irq_enter(void); extern void rcu_irq_exit(void); + +#ifdef CONFIG_RCU_USER_QS extern void rcu_user_enter(void); extern void rcu_user_exit(void); extern void rcu_user_enter_irq(void); extern void rcu_user_exit_irq(void); +#else +static inline void rcu_user_enter(void) { } +static inline void rcu_user_exit(void) { } +#endif /* CONFIG_RCU_USER_QS */ + + extern void exit_rcu(void); /** 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 + help + This option sets hooks on kernel / userspace boundaries and + puts RCU in extended quiescent state when the CPU runs in + userspace. It means that when a CPU runs in userspace, it is + excluded from the global RCU state machine and thus doesn't + to keep the timer tick on for RCU. + config RCU_FANOUT int "Tree-based hierarchical RCU fanout value" range 2 64 if 64BIT diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 5541a07..efa5983 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -423,6 +423,7 @@ void rcu_idle_enter(void) } EXPORT_SYMBOL_GPL(rcu_idle_enter); +#ifdef CONFIG_RCU_USER_QS /** * rcu_user_enter - inform RCU that we are resuming userspace. * @@ -437,7 +438,6 @@ void rcu_user_enter(void) } EXPORT_SYMBOL_GPL(rcu_user_enter); - /** * rcu_user_enter_irq - inform RCU that we are going to resume userspace * after the current irq returns. @@ -458,6 +458,7 @@ void rcu_user_enter_irq(void) rdtp->dynticks_nesting = 1; local_irq_restore(flags); } +#endif /** * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle @@ -561,6 +562,7 @@ void rcu_idle_exit(void) } EXPORT_SYMBOL_GPL(rcu_idle_exit); +#ifdef CONFIG_RCU_USER_QS /** * rcu_user_exit - inform RCU that we are exiting userspace. * @@ -594,6 +596,7 @@ void rcu_user_exit_irq(void) rdtp->dynticks_nesting += DYNTICK_TASK_EXIT_IDLE; local_irq_restore(flags); } +#endif /** * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
