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authorTejun Heo <tj@kernel.org>2010-06-08 21:40:37 +0200
committerTejun Heo <tj@kernel.org>2010-06-08 21:40:37 +0200
commit21aa9af03d06cb1d19a3738e5cf12acff984e69b (patch)
treee205a742a4a9baf098b4e3d428c04f4d3a065bca /kernel/sched.c
parent9ed3811a6c0d6b66e6cd47a5d7b9136386dce743 (diff)
sched: add hooks for workqueue
Concurrency managed workqueue needs to know when workers are going to sleep and waking up. Using these two hooks, cmwq keeps track of the current concurrency level and throttles execution of new works if it's too high and wakes up another worker from the sleep hook if it becomes too low. This patch introduces PF_WQ_WORKER to identify workqueue workers and adds the following two hooks. * wq_worker_waking_up(): called when a worker is woken up. * wq_worker_sleeping(): called when a worker is going to sleep and may return a pointer to a local task which should be woken up. The returned task is woken up using try_to_wake_up_local() which is simplified ttwu which is called under rq lock and can only wake up local tasks. Both hooks are currently defined as noop in kernel/workqueue_sched.h. Later cmwq implementation will replace them with proper implementation. These hooks are hard coded as they'll always be enabled. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c53
1 files changed, 51 insertions, 2 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 96eafd5f345..edd5a54b95d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -77,6 +77,7 @@
#include <asm/irq_regs.h>
#include "sched_cpupri.h"
+#include "workqueue_sched.h"
#define CREATE_TRACE_POINTS
#include <trace/events/sched.h>
@@ -2306,6 +2307,9 @@ static inline void ttwu_post_activation(struct task_struct *p, struct rq *rq,
rq->idle_stamp = 0;
}
#endif
+ /* if a worker is waking up, notify workqueue */
+ if ((p->flags & PF_WQ_WORKER) && success)
+ wq_worker_waking_up(p, cpu_of(rq));
}
/**
@@ -2414,6 +2418,37 @@ out:
}
/**
+ * try_to_wake_up_local - try to wake up a local task with rq lock held
+ * @p: the thread to be awakened
+ *
+ * Put @p on the run-queue if it's not alredy there. The caller must
+ * ensure that this_rq() is locked, @p is bound to this_rq() and not
+ * the current task. this_rq() stays locked over invocation.
+ */
+static void try_to_wake_up_local(struct task_struct *p)
+{
+ struct rq *rq = task_rq(p);
+ bool success = false;
+
+ BUG_ON(rq != this_rq());
+ BUG_ON(p == current);
+ lockdep_assert_held(&rq->lock);
+
+ if (!(p->state & TASK_NORMAL))
+ return;
+
+ if (!p->se.on_rq) {
+ if (likely(!task_running(rq, p))) {
+ schedstat_inc(rq, ttwu_count);
+ schedstat_inc(rq, ttwu_local);
+ }
+ ttwu_activate(p, rq, false, false, true, ENQUEUE_WAKEUP);
+ success = true;
+ }
+ ttwu_post_activation(p, rq, 0, success);
+}
+
+/**
* wake_up_process - Wake up a specific process
* @p: The process to be woken up.
*
@@ -3618,10 +3653,24 @@ need_resched_nonpreemptible:
clear_tsk_need_resched(prev);
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
- if (unlikely(signal_pending_state(prev->state, prev)))
+ if (unlikely(signal_pending_state(prev->state, prev))) {
prev->state = TASK_RUNNING;
- else
+ } else {
+ /*
+ * If a worker is going to sleep, notify and
+ * ask workqueue whether it wants to wake up a
+ * task to maintain concurrency. If so, wake
+ * up the task.
+ */
+ if (prev->flags & PF_WQ_WORKER) {
+ struct task_struct *to_wakeup;
+
+ to_wakeup = wq_worker_sleeping(prev, cpu);
+ if (to_wakeup)
+ try_to_wake_up_local(to_wakeup);
+ }
deactivate_task(rq, prev, DEQUEUE_SLEEP);
+ }
switch_count = &prev->nvcsw;
}