Re: linux-next RCU complaint during boot

[Paul E. McKenney]

On Thu, Sep 01, 2011 at 12:33:37PM -0400, Valdis.Kletnieks@xxxxxx wrote:
> Seen during boot of linux-next 20110831:
> 
> [    8.823047] ------------[ cut here ]------------
> [    8.823177] WARNING: at kernel/rcutree.c:1821 rcu_needs_cpu_quick_check+0x6e/0x204()
> [    8.823314] Hardware name: Latitude E6500
> [    8.823418] Modules linked in:
> [    8.823601] Pid: 0, comm: swapper Not tainted 3.1.0-rc4-next-20110831-dirty #11
> [    8.823724] Call Trace:
> [    8.823824]  <IRQ>  [<ffffffff81039682>] warn_slowpath_common+0x7e/0x96
> [    8.824015]  [<ffffffff81092467>] ? note_new_gpnum+0x32/0x96
> [    8.824034]  [<ffffffff810396af>] warn_slowpath_null+0x15/0x17
> [    8.824034]  [<ffffffff810917de>] rcu_needs_cpu_quick_check+0x6e/0x204
> [    8.824034]  [<ffffffff81093df8>] rcu_needs_cpu+0x9/0xd
> [    8.824034]  [<ffffffff81065933>] tick_nohz_stop_sched_tick+0x20a/0x420
> [    8.824034]  [<ffffffff8103fd77>] irq_exit+0xd2/0xe0
> [    8.824034]  [<ffffffff81018f91>] smp_apic_timer_interrupt+0x8b/0x99
> [    8.824034]  [<ffffffff815a1b30>] apic_timer_interrupt+0x70/0x80
> [    8.824034]  <EOI>  [<ffffffff8159dbbf>] ? notifier_call_chain+0x20/0x81
> [    8.824034]  [<ffffffff8159dc7e>] __atomic_notifier_call_chain+0x5e/0x90
> [    8.824034]  [<ffffffff8159dc20>] ? notifier_call_chain+0x81/0x81
> [    8.824034]  [<ffffffff8159dcbf>] atomic_notifier_call_chain+0xf/0x11
> [    8.824034]  [<ffffffff8100092d>] cpu_idle+0xaf/0x102
> [    8.824034]  [<ffffffff81569ddc>] rest_init+0xd0/0xd7
> [    8.824034]  [<ffffffff81569d0c>] ? csum_partial_copy_generic+0x16c/0x16c
> [    8.824034]  [<ffffffff81b31b09>] start_kernel+0x375/0x380
> [    8.824034]  [<ffffffff81b3129f>] x86_64_start_reservations+0xaf/0xb3
> [    8.824034]  [<ffffffff81b31393>] x86_64_start_kernel+0xf0/0xf7
> [    8.824034] ---[ end trace f6289633ba846f8f ]---
> 
> Any ideas?

This is a bug where someone uses RCU at a time when RCU has been told
that the CPU is in dyntick-idle mode.  Frederic Weisbecker has some
patches that should address this.

							Thanx, Paul
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