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 <fweis...@gmail.com>
Cc: Alessio Igor Bogani <abog...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Avi Kivity <a...@redhat.com>
Cc: Chris Metcalf <cmetc...@tilera.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Geoff Levand <ge...@infradead.org>
Cc: Gilad Ben Yossef <gi...@benyossef.com>
Cc: Hakan Akkan <hakanak...@gmail.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Josh Triplett <j...@joshtriplett.org>
Cc: Kevin Hilman <khil...@ti.com>
Cc: Max Krasnyansky <m...@qualcomm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Stephen Hemminger <shemmin...@vyatta.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporat...@gmail.com>
Cc: Thomas Gleixner <t...@linutronix.de>
---
arch/um/drivers/mconsole_kern.c | 2 +-
include/linux/rcupdate.h | 2 ++
include/linux/sched.h | 20 +++++++++++---------
kernel/rcutree.c | 15 +++++++++++++++
kernel/sched/core.c | 2 +-
5 files changed, 30 insertions(+), 11 deletions(-)
diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 88e466b..e61922d 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -705,7 +705,7 @@ static void stack_proc(void *arg)
struct task_struct *from = current, *to = arg;
to->thread.saved_task = from;
- rcu_switch_from(from);
+ rcu_switch(from, to);
switch_to(from, to, from);
}
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index a72f25e..1e57888 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -198,6 +198,8 @@ 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);
+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 4059c0f..e17fcd0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1871,23 +1871,25 @@ static inline void rcu_copy_process(struct task_struct
*p)
INIT_LIST_HEAD(&p->rcu_node_entry);
}
-static inline void rcu_switch_from(struct task_struct *prev)
-{
- if (prev->rcu_read_lock_nesting != 0)
- rcu_preempt_note_context_switch();
-}
-
#else
static inline void rcu_copy_process(struct task_struct *p)
{
}
-static inline void rcu_switch_from(struct task_struct *prev)
-{
-}
+#endif
+static inline void rcu_switch(struct task_struct *prev,
+ struct task_struct *next)
+{
+#ifdef CONFIG_PREEMPT_RCU
+ if (prev->rcu_read_lock_nesting != 0)
+ rcu_preempt_note_context_switch();
+#endif
+#ifdef CONFIG_RCU_USER_QS
+ rcu_user_hooks_switch(prev, next);
#endif
+}
#ifdef CONFIG_SMP
extern void do_set_cpus_allowed(struct task_struct *p,
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 78b0c30..2d79308 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -720,6 +720,21 @@ 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
+
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
/*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d5594a4..fa61d8a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2081,7 +2081,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
#endif
/* Here we just switch the register state and the stack. */
- rcu_switch_from(prev);
+ rcu_switch(prev, next);
switch_to(prev, next, prev);
barrier();
--
1.7.5.4
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