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rcu: Switch task's syscall hooks on context switch

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Clear the syscalls hook of a task when it's scheduled out so that if
the task migrates, it doesn't run the syscall slow path on a CPU
that might not need it.

Also set the syscalls hook on the next task if needed.

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 2012-07-16 15:06:40 -07:00
parent 1e1a689f10
commit 04e7e95153
5 changed files with 27 additions and 0 deletions
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1
arch/um/drivers/mconsole_kern.c
View file

@ -705,6 +705,7 @@ static void stack_proc(void *arg)
struct task_struct *from = current, *to = arg;
to->thread.saved_task = from;
rcu_switch(from, to);
switch_to(from, to, from);
}

2
include/linux/rcupdate.h
View file

@ -197,6 +197,8 @@ 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);
extern void rcu_user_hooks_switch(struct task_struct *prev,
struct task_struct *next);
#else
static inline void rcu_user_enter(void) { }
static inline void rcu_user_exit(void) { }

8
include/linux/sched.h
View file

@ -1885,6 +1885,14 @@ static inline void rcu_copy_process(struct task_struct *p)
#endif
static inline void rcu_switch(struct task_struct *prev,
struct task_struct *next)
{
#ifdef CONFIG_RCU_USER_QS
rcu_user_hooks_switch(prev, next);
#endif
}
static inline void tsk_restore_flags(struct task_struct *task,
unsigned long orig_flags, unsigned long flags)
{

15
kernel/rcutree.c
View file

@ -717,6 +717,21 @@ int rcu_is_cpu_idle(void)
}
EXPORT_SYMBOL(rcu_is_cpu_idle);
#ifdef CONFIG_RCU_USER_QS
void rcu_user_hooks_switch(struct task_struct *prev,
struct task_struct *next)
{
struct rcu_dynticks *rdtp;
/* Interrupts are disabled in context switch */
rdtp = &__get_cpu_var(rcu_dynticks);
if (!rdtp->ignore_user_qs) {
clear_tsk_thread_flag(prev, TIF_NOHZ);
set_tsk_thread_flag(next, TIF_NOHZ);
}
}
#endif /* #ifdef CONFIG_RCU_USER_QS */
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
/*

1
kernel/sched/core.c
View file

@ -2081,6 +2081,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
#endif
/* Here we just switch the register state and the stack. */
rcu_switch(prev, next);
switch_to(prev, next, prev);
barrier();