From 98f1b5a762f7bee20785ed576630386ddcc62483 Mon Sep 17 00:00:00 2001 From: Grygorii Strashko Date: Tue, 8 May 2018 15:19:40 +0100 Subject: [PATCH] ARM: 8765/1: smp: Move clear_tasks_mm_cpumask() call to __cpu_die() Suspending a CPU on a RT kernel results in the following backtrace: | Disabling non-boot CPUs ... | BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917 | in_atomic(): 1, irqs_disabled(): 128, pid: 18, name: migration/1 | INFO: lockdep is turned off. | irq event stamp: 122 | hardirqs last enabled at (121): [] _raw_spin_unlock_irqrestore+0x88/0x90 | hardirqs last disabled at (122): [] _raw_spin_lock_irq+0x28/0x5c | CPU: 1 PID: 18 Comm: migration/1 Tainted: G W 4.1.4-rt3-01046-g96ac8da #204 | Hardware name: Generic DRA74X (Flattened Device Tree) | [] (unwind_backtrace) from [] (show_stack+0x20/0x24) | [] (show_stack) from [] (dump_stack+0x88/0xdc) | [] (dump_stack) from [] (___might_sleep+0x198/0x2a8) | [] (___might_sleep) from [] (rt_spin_lock+0x30/0x70) | [] (rt_spin_lock) from [] (find_lock_task_mm+0x9c/0x174) | [] (find_lock_task_mm) from [] (clear_tasks_mm_cpumask+0xb4/0x1ac) | [] (clear_tasks_mm_cpumask) from [] (__cpu_disable+0x98/0xbc) | [] (__cpu_disable) from [] (take_cpu_down+0x1c/0x50) | [] (take_cpu_down) from [] (multi_cpu_stop+0x11c/0x158) | [] (multi_cpu_stop) from [] (cpu_stopper_thread+0xc4/0x184) | [] (cpu_stopper_thread) from [] (smpboot_thread_fn+0x18c/0x324) | [] (smpboot_thread_fn) from [] (kthread+0xe8/0x104) | [] (kthread) from [] (ret_from_fork+0x14/0x3c) | CPU1: shutdown The root cause of above backtrace is task_lock() which takes a sleeping lock on -RT. To fix the issue, move clear_tasks_mm_cpumask() call from __cpu_disable() to __cpu_die() which is called on the thread which is asking for a target CPU to be shutdown. In addition, this change restores CPU hotplug functionality on ARM CPU1 can be unplugged/plugged many times. Link: http://lkml.kernel.org/r/1441995683-30817-1-git-send-email-grygorii.strashko@ti.com [bigeasy: slighty edited the commit message] Signed-off-by: Grygorii Strashko Cc: Cc: Sekhar Nori Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Russell King --- arch/arm/kernel/smp.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 2da087926ebe..b9e08f50df41 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -236,8 +236,6 @@ int __cpu_disable(void) flush_cache_louis(); local_flush_tlb_all(); - clear_tasks_mm_cpumask(cpu); - return 0; } @@ -255,6 +253,7 @@ void __cpu_die(unsigned int cpu) } pr_debug("CPU%u: shutdown\n", cpu); + clear_tasks_mm_cpumask(cpu); /* * platform_cpu_kill() is generally expected to do the powering off * and/or cutting of clocks to the dying CPU. Optionally, this may