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 <[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/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 -- 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/
