> Perhaps what is happening is that cpu0 comes online ... safely skips > over the early printk calls. Calls cpu_init() which sets up the resources > *it* needs (ar.k3 points to per-cpu space), and then executes > sched_init() which marks it safe for all printk's. Then cpu1 comes > up and does a printk before it gets to cpu_init().
I just tried Ingo's patch[1] on a 2.6.25-rc2 kernel with printk timestamps turned on ... and it booted just fine on my tiger4. The default path for non-boot cpus is from head.S to start_secondary(), and that calls cpu_init() pretty quickly. There shouldn't normally[2] be any printk() calls on the non-boot cpu before it is safe to do so. -Tony [1] Attached [2] If you set #define SMP_DEBUG in arch/ia64/kernel/smpboot.c that enables at least one printk() that will cause problems if you have also configured timestamps.
kernel/sched.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) Index: linux-x86.q/kernel/sched.c =================================================================== --- linux-x86.q.orig/kernel/sched.c +++ linux-x86.q/kernel/sched.c @@ -666,6 +666,8 @@ const_debug unsigned int sysctl_sched_rt */ const_debug unsigned int sysctl_sched_rt_ratio = 62259; +static __read_mostly int scheduler_running; + /* * For kernel-internal use: high-speed (but slightly incorrect) per-cpu * clock constructed from sched_clock(): @@ -676,14 +678,16 @@ unsigned long long cpu_clock(int cpu) unsigned long flags; struct rq *rq; - local_irq_save(flags); - rq = cpu_rq(cpu); /* * Only call sched_clock() if the scheduler has already been * initialized (some code might call cpu_clock() very early): */ - if (rq->idle) - update_rq_clock(rq); + if (unlikely(!scheduler_running)) + return 0; + + local_irq_save(flags); + rq = cpu_rq(cpu); + update_rq_clock(rq); now = rq->clock; local_irq_restore(flags); @@ -7255,6 +7259,8 @@ void __init sched_init(void) * During early bootup we pretend to be a normal task: */ current->sched_class = &fair_sched_class; + + scheduler_running = 1; } #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP --
