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rcu: Settle config for userspace extended quiescent state 

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>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Frederic Weisbecker 2012-07-11 20:26:30 +02:00
parent 9a0c6fef42
commit 2b1d5024e1
4 changed files with 33 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/Kconfig
View File

@ -281,4 +281,14 @@ 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"

9
include/linux/rcupdate.h
View File

@ -191,10 +191,19 @@ 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_after_irq(void);
extern void rcu_user_exit_after_irq(void);
#else
static inline void rcu_user_enter(void) { }
static inline void rcu_user_exit(void) { }
static inline void rcu_user_enter_after_irq(void) { }
static inline void rcu_user_exit_after_irq(void) { }
#endif /* CONFIG_RCU_USER_QS */
extern void exit_rcu(void);
/**

10
init/Kconfig
View File

@ -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

5
kernel/rcutree.c
View File

@ -400,6 +400,7 @@ 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.
*
@ -424,7 +425,6 @@ void rcu_user_enter(void)
rcu_eqs_enter(1);
}
/**
* rcu_user_enter_after_irq - inform RCU that we are going to resume userspace
* after the current irq returns.
@ -445,6 +445,7 @@ void rcu_user_enter_after_irq(void)
rdtp->dynticks_nesting = 1;
local_irq_restore(flags);
}
#endif /* CONFIG_RCU_USER_QS */
/**
* rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
@ -548,6 +549,7 @@ 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.
*
@ -591,6 +593,7 @@ void rcu_user_exit_after_irq(void)
rdtp->dynticks_nesting += DYNTICK_TASK_EXIT_IDLE;
local_irq_restore(flags);
}
#endif /* CONFIG_RCU_USER_QS */
/**
* rcu_irq_enter - inform RCU that current CPU is entering irq away from idle