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Jon Fraser authored
CPU interrupts need to be disabled on a cpu being taken down. When a cpu is hot-plugged out of the system the following sequence occurs. On the CPU where the hotplug sequence was initiated: cpu_down _cpu_down { __cpu_notify(CPU_DOWN_PREPARE __stop_machine(take_cpu_down wait for cpu to run disable code. __cpu_die } On the CPU being disabled: take_cpu_down __cpu_disable { mp_ops->cpu_disable bmips_cpu_disable clear_c0_status(IE_IRQ5) (added) cpu_notify(CPU_DYING... } Before the cpu_notifier is called with CPU_DYING, all interrupts on the dying cpu must be disabled. This guarantees that before tick_notify is called with the CPU_DYING event and sets the clock device pointer to NULL, there can not be any more clock interrupts. When this wasn't done, an unfortunately-timed timer interrupt sometimes caused hangs immediately prior to system suspend: Debug PM is not enabled. To enable partial suspend, rebuild kernel with CONFIG_PM_DEBUG Pass 1 out of 1,PM: Syncing filesystems ... mode=none, tp1=done. 1, flags=5, cycle_tp=, sleep= Freezing user space processes ... (elapsed 0.01 seconds) done. Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done. PM: suspend of devices complete after 54.199 msecs PM: late suspend of devices complete after 0.172 msecs Disabling non-boot CPUs ... SMP: CPU1 is offline INFO: rcu_sched detected stalls on CPUs/tasks: { 3} (detected by 0, t=62537 jiffies) Call Trace: [<804baa78>] dump_stack+0x8/0x34 [<8008a2d8>] __rcu_pending+0x4b8/0x55c [<8008adf4>] rcu_check_callbacks+0x78/0x180 [<80037830>] update_process_times+0x40/0x6c [<80072fe4>] tick_sched_timer+0x74/0xe4 [<80050180>] __run_hrtimer.clone.30+0x64/0x140 [<80051150>] hrtimer_interrupt+0x19c/0x4bc [<8000cdb8>] c0_compare_interrupt+0x50/0x88 [<80081b18>] handle_irq_event_percpu+0x5c/0x2f4 [<80086490>] handle_percpu_irq+0x8c/0xc0 [<800811b4>] generic_handle_irq+0x34/0x54 [<800067dc>] do_IRQ+0x18/0x2c [<8000375c>] plat_irq_dispatch+0xd0/0x128 [<80004a04>] ret_from_irq+0x0/0x4 [<80004c40>] r4k_wait+0x20/0x40 [<80006b6c>] cpu_idle+0x98/0xf0 [<805d3988>] start_kernel+0x424/0x440 Signed-off-by: Jon Fraser <jfraser@broadcom.com> Signed-off-by: Kevin Cernekee <cernekee@gmail.com> Cc: f.fainelli@gmail.com Cc: mbizon@freebox.fr Cc: jogo@openwrt.org Cc: linux-mips@linux-mips.org Cc: devicetree@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/8160/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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