From f340c0d1a3f40fdcba69cd291530a4debc58748f Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 28 Jun 2005 16:40:42 +0200 Subject: [PATCH] [PATCH] Tweak idle thread setup semantics This patch tweaks idle thread setup semantics a bit: instead of setting NEED_RESCHED in init_idle(), we do an explicit schedule() before calling into cpu_idle(). This patch, while having no negative side-effects, enables wider use of cond_resched()s. (which might happen in the stock kernel too, but it's particulary important for voluntary-preempt) Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/main.c | 7 +++++++ kernel/sched.c | 9 ++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/init/main.c b/init/main.c index d324801729b..b5e421e39ed 100644 --- a/init/main.c +++ b/init/main.c @@ -383,6 +383,13 @@ static void noinline rest_init(void) numa_default_policy(); unlock_kernel(); preempt_enable_no_resched(); + + /* + * The boot idle thread must execute schedule() + * at least one to get things moving: + */ + schedule(); + cpu_idle(); } diff --git a/kernel/sched.c b/kernel/sched.c index e2b0d3e4dd0..5f2182d4224 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4166,6 +4166,14 @@ void show_state(void) read_unlock(&tasklist_lock); } +/** + * init_idle - set up an idle thread for a given CPU + * @idle: task in question + * @cpu: cpu the idle task belongs to + * + * NOTE: this function does not set the idle thread's NEED_RESCHED + * flag, to make booting more robust. + */ void __devinit init_idle(task_t *idle, int cpu) { runqueue_t *rq = cpu_rq(cpu); @@ -4183,7 +4191,6 @@ void __devinit init_idle(task_t *idle, int cpu) #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW) idle->oncpu = 1; #endif - set_tsk_need_resched(idle); spin_unlock_irqrestore(&rq->lock, flags); /* Set the preempt count _outside_ the spinlocks! */