diff options
| -rw-r--r-- | include/linux/context_tracking.h | 10 | ||||
| -rw-r--r-- | include/linux/sched.h | 3 | ||||
| -rw-r--r-- | kernel/context_tracking.c | 44 | ||||
| -rw-r--r-- | kernel/sched/core.c | 1 |
4 files changed, 22 insertions, 36 deletions
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 2821838256b4..b96bd299966f 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -14,8 +14,6 @@ extern void context_tracking_enter(enum ctx_state state); extern void context_tracking_exit(enum ctx_state state); extern void context_tracking_user_enter(void); extern void context_tracking_user_exit(void); -extern void __context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next); static inline void user_enter(void) { @@ -51,19 +49,11 @@ static inline void exception_exit(enum ctx_state prev_ctx) } } -static inline void context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next) -{ - if (context_tracking_is_enabled()) - __context_tracking_task_switch(prev, next); -} #else static inline void user_enter(void) { } static inline void user_exit(void) { } static inline enum ctx_state exception_enter(void) { return 0; } static inline void exception_exit(enum ctx_state prev_ctx) { } -static inline void context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next) { } #endif /* !CONFIG_CONTEXT_TRACKING */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 26a2e6122734..185a750e4ed4 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2532,6 +2532,9 @@ static inline unsigned long wait_task_inactive(struct task_struct *p, } #endif +#define tasklist_empty() \ + list_empty(&init_task.tasks) + #define next_task(p) \ list_entry_rcu((p)->tasks.next, struct task_struct, tasks) diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 5b11a10e196a..0a495ab35bc7 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -30,14 +30,6 @@ EXPORT_SYMBOL_GPL(context_tracking_enabled); DEFINE_PER_CPU(struct context_tracking, context_tracking); EXPORT_SYMBOL_GPL(context_tracking); -void context_tracking_cpu_set(int cpu) -{ - if (!per_cpu(context_tracking.active, cpu)) { - per_cpu(context_tracking.active, cpu) = true; - static_key_slow_inc(&context_tracking_enabled); - } -} - static bool context_tracking_recursion_enter(void) { int recursion; @@ -193,24 +185,26 @@ void context_tracking_user_exit(void) } NOKPROBE_SYMBOL(context_tracking_user_exit); -/** - * __context_tracking_task_switch - context switch the syscall callbacks - * @prev: the task that is being switched out - * @next: the task that is being switched in - * - * The context tracking uses the syscall slow path to implement its user-kernel - * boundaries probes on syscalls. This way it doesn't impact the syscall fast - * path on CPUs that don't do context tracking. - * - * But we need to clear the flag on the previous task because it may later - * migrate to some CPU that doesn't do the context tracking. As such the TIF - * flag may not be desired there. - */ -void __context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next) +void __init context_tracking_cpu_set(int cpu) { - clear_tsk_thread_flag(prev, TIF_NOHZ); - set_tsk_thread_flag(next, TIF_NOHZ); + static __initdata bool initialized = false; + + if (!per_cpu(context_tracking.active, cpu)) { + per_cpu(context_tracking.active, cpu) = true; + static_key_slow_inc(&context_tracking_enabled); + } + + if (initialized) + return; + + /* + * Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork + * This assumes that init is the only task at this early boot stage. + */ + set_tsk_thread_flag(&init_task, TIF_NOHZ); + WARN_ON_ONCE(!tasklist_empty()); + + initialized = true; } #ifdef CONFIG_CONTEXT_TRACKING_FORCE diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fe22f7510bce..54f032cea040 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2332,7 +2332,6 @@ context_switch(struct rq *rq, struct task_struct *prev, */ spin_release(&rq->lock.dep_map, 1, _THIS_IP_); - context_tracking_task_switch(prev, next); /* Here we just switch the register state and the stack. */ switch_to(prev, next, prev); barrier(); |