diff options
| -rw-r--r-- | include/linux/sched.h | 52 | ||||
| -rw-r--r-- | include/linux/sched/sysctl.h | 1 | ||||
| -rw-r--r-- | kernel/sched/core.c | 17 | ||||
| -rw-r--r-- | kernel/sched/fair.c | 7 | ||||
| -rw-r--r-- | kernel/sysctl.c | 7 |
5 files changed, 45 insertions, 39 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 348f51b0ec92..3762fe4e3a80 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -262,20 +262,9 @@ extern char ___assert_task_state[1 - 2*!!( #define set_task_state(tsk, state_value) \ do { \ (tsk)->task_state_change = _THIS_IP_; \ - smp_store_mb((tsk)->state, (state_value)); \ + smp_store_mb((tsk)->state, (state_value)); \ } while (0) -/* - * set_current_state() includes a barrier so that the write of current->state - * is correctly serialised wrt the caller's subsequent test of whether to - * actually sleep: - * - * set_current_state(TASK_UNINTERRUPTIBLE); - * if (do_i_need_to_sleep()) - * schedule(); - * - * If the caller does not need such serialisation then use __set_current_state() - */ #define __set_current_state(state_value) \ do { \ current->task_state_change = _THIS_IP_; \ @@ -284,11 +273,19 @@ extern char ___assert_task_state[1 - 2*!!( #define set_current_state(state_value) \ do { \ current->task_state_change = _THIS_IP_; \ - smp_store_mb(current->state, (state_value)); \ + smp_store_mb(current->state, (state_value)); \ } while (0) #else +/* + * @tsk had better be current, or you get to keep the pieces. + * + * The only reason is that computing current can be more expensive than + * using a pointer that's already available. + * + * Therefore, see set_current_state(). + */ #define __set_task_state(tsk, state_value) \ do { (tsk)->state = (state_value); } while (0) #define set_task_state(tsk, state_value) \ @@ -299,11 +296,34 @@ extern char ___assert_task_state[1 - 2*!!( * is correctly serialised wrt the caller's subsequent test of whether to * actually sleep: * + * for (;;) { * set_current_state(TASK_UNINTERRUPTIBLE); - * if (do_i_need_to_sleep()) - * schedule(); + * if (!need_sleep) + * break; + * + * schedule(); + * } + * __set_current_state(TASK_RUNNING); + * + * If the caller does not need such serialisation (because, for instance, the + * condition test and condition change and wakeup are under the same lock) then + * use __set_current_state(). + * + * The above is typically ordered against the wakeup, which does: + * + * need_sleep = false; + * wake_up_state(p, TASK_UNINTERRUPTIBLE); + * + * Where wake_up_state() (and all other wakeup primitives) imply enough + * barriers to order the store of the variable against wakeup. + * + * Wakeup will do: if (@state & p->state) p->state = TASK_RUNNING, that is, + * once it observes the TASK_UNINTERRUPTIBLE store the waking CPU can issue a + * TASK_RUNNING store which can collide with __set_current_state(TASK_RUNNING). + * + * This is obviously fine, since they both store the exact same value. * - * If the caller does not need such serialisation then use __set_current_state() + * Also see the comments of try_to_wake_up(). */ #define __set_current_state(state_value) \ do { current->state = (state_value); } while (0) diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index 22db1e63707e..441145351301 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -36,7 +36,6 @@ extern unsigned int sysctl_numa_balancing_scan_size; extern unsigned int sysctl_sched_migration_cost; extern unsigned int sysctl_sched_nr_migrate; extern unsigned int sysctl_sched_time_avg; -extern unsigned int sysctl_sched_shares_window; int sched_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *length, diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 154fd689fe02..f3cfa0dd5b34 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1995,14 +1995,15 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * @state: the mask of task states that can be woken * @wake_flags: wake modifier flags (WF_*) * - * Put it on the run-queue if it's not already there. The "current" - * thread is always on the run-queue (except when the actual - * re-schedule is in progress), and as such you're allowed to do - * the simpler "current->state = TASK_RUNNING" to mark yourself - * runnable without the overhead of this. - * - * Return: %true if @p was woken up, %false if it was already running. - * or @state didn't match @p's state. + * If (@state & @p->state) @p->state = TASK_RUNNING. + * + * If the task was not queued/runnable, also place it back on a runqueue. + * + * Atomic against schedule() which would dequeue a task, also see + * set_current_state(). + * + * Return: %true if @p->state changes (an actual wakeup was done), + * %false otherwise. */ static int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c242944f5cbd..3cf446c53043 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -93,13 +93,6 @@ unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; -/* - * The exponential sliding window over which load is averaged for shares - * distribution. - * (default: 10msec) - */ -unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; - #ifdef CONFIG_CFS_BANDWIDTH /* * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 706309f9ed84..739fb17371af 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -347,13 +347,6 @@ static struct ctl_table kern_table[] = { .mode = 0644, .proc_handler = proc_dointvec, }, - { - .procname = "sched_shares_window_ns", - .data = &sysctl_sched_shares_window, - .maxlen = sizeof(unsigned int), - .mode = 0644, - .proc_handler = proc_dointvec, - }, #ifdef CONFIG_SCHEDSTATS { .procname = "sched_schedstats", |