Commit-ID: 04e7e951532b390b16feb070be9972b8fad2fc57
Gitweb: http://git.kernel.org/tip/04e7e951532b390b16feb070be9972b8fad2fc57
Author: Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Mon, 16 Jul 2012 15:06:40 -0700
Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CommitDate: Wed, 26 Sep 2012 15:47:02 +0200
rcu: Switch task's syscall hooks on context switch
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@xxxxxxxxx>
Cc: Alessio Igor Bogani <abogani@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Geoff Levand <geoff@xxxxxxxxxxxxx>
Cc: Gilad Ben Yossef <gilad@xxxxxxxxxxxxx>
Cc: Hakan Akkan <hakanakkan@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Kevin Hilman <khilman@xxxxxx>
Cc: Max Krasnyansky <maxk@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephen Hemminger <shemminger@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Sven-Thorsten Dietrich <thebigcorporation@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
arch/um/drivers/mconsole_kern.c | 1 +
include/linux/rcupdate.h | 2 ++
include/linux/sched.h | 8 ++++++++
kernel/rcutree.c | 15 +++++++++++++++
kernel/sched/core.c | 1 +
5 files changed, 27 insertions(+), 0 deletions(-)
diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 664a60e..c17de0d 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -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);
}
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f5034f2..7c968e4 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -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) { }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 23bddac..335720a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -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)
{
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 6b82a95..d2e74c8 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -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)
/*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1a48cdb..ea2213b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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();
--
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