sched: Create more preempt_count accessors

We need a few special preempt_count accessors:
 - task_preempt_count() for when we're interested in the preemption
   count of another (non-running) task.
 - init_task_preempt_count() for properly initializing the preemption
   count.
 - init_idle_preempt_count() a special case of the above for the idle
   threads.

With these no generic code ever touches thread_info::preempt_count
anymore and architectures could choose to remove it.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index a1fc659..8100b1e 100644 (file)
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -28,6 +28,20 @@ static __always_inline void preempt_count_set(int pc)
 }
 
 /*
+ * must be macros to avoid header recursion hell
+ */
+#define task_preempt_count(p) \
+       (task_thread_info(p)->preempt_count & ~PREEMPT_NEED_RESCHED)
+
+#define init_task_preempt_count(p) do { \
+       task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
+} while (0)
+
+#define init_idle_preempt_count(p, cpu) do { \
+       task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \
+} while (0)
+
+/*
  * We fold the NEED_RESCHED bit into the preempt count such that
  * preempt_enable() can decrement and test for needing to reschedule with a
  * single instruction.

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 2e7d994..613381b 100644 (file)
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -100,7 +100,7 @@ static inline long __trace_sched_switch_state(struct task_struct *p)
        /*
         * For all intents and purposes a preempted task is a running task.
         */
-       if (task_thread_info(p)->preempt_count & PREEMPT_ACTIVE)
+       if (task_preempt_count(p) & PREEMPT_ACTIVE)
                state = TASK_RUNNING | TASK_STATE_MAX;
 #endif
 

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ee61f5a..0ba4e41 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -983,7 +983,7 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
         * ttwu() will sort out the placement.
         */
        WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
-                       !(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));
+                       !(task_preempt_count(p) & PREEMPT_ACTIVE));
 
 #ifdef CONFIG_LOCKDEP
        /*
@@ -1723,8 +1723,7 @@ void sched_fork(struct task_struct *p)
        p->on_cpu = 0;
 #endif
 #ifdef CONFIG_PREEMPT_COUNT
-       /* Want to start with kernel preemption disabled. */
-       task_thread_info(p)->preempt_count = PREEMPT_DISABLED;
+       init_task_preempt_count(p);
 #endif
 #ifdef CONFIG_SMP
        plist_node_init(&p->pushable_tasks, MAX_PRIO);
@@ -4217,7 +4216,7 @@ void init_idle(struct task_struct *idle, int cpu)
        raw_spin_unlock_irqrestore(&rq->lock, flags);
 
        /* Set the preempt count _outside_ the spinlocks! */
-       task_thread_info(idle)->preempt_count = PREEMPT_ENABLED;
+       init_idle_preempt_count(idle, cpu);
 
        /*
         * The idle tasks have their own, simple scheduling class: