| From fde165b2a29673aabf18ceff14dea1f1cfb0daad Mon Sep 17 00:00:00 2001 |
| From: Colin Cross <ccross@android.com> |
| Date: Sat, 5 May 2012 20:58:13 +0100 |
| Subject: ARM: 7414/1: SMP: prevent use of the console when using idmap_pgd |
| |
| From: Colin Cross <ccross@android.com> |
| |
| commit fde165b2a29673aabf18ceff14dea1f1cfb0daad upstream. |
| |
| Commit 4e8ee7de227e3ab9a72040b448ad728c5428a042 (ARM: SMP: use |
| idmap_pgd for mapping MMU enable during secondary booting) |
| switched secondary boot to use idmap_pgd, which is initialized |
| during early_initcall, instead of a page table initialized during |
| __cpu_up. This causes idmap_pgd to contain the static mappings |
| but be missing all dynamic mappings. |
| |
| If a console is registered that creates a dynamic mapping, the |
| printk in secondary_start_kernel will trigger a data abort on |
| the missing mapping before the exception handlers have been |
| initialized, leading to a hang. Initial boot is not affected |
| because no consoles have been registered, and resume is usually |
| not affected because the offending console is suspended. |
| Onlining a cpu with hotplug triggers the problem. |
| |
| A workaround is to the printk in secondary_start_kernel until |
| after the page tables have been switched back to init_mm. |
| |
| Signed-off-by: Colin Cross <ccross@android.com> |
| Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/arm/kernel/smp.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- a/arch/arm/kernel/smp.c |
| +++ b/arch/arm/kernel/smp.c |
| @@ -255,8 +255,6 @@ asmlinkage void __cpuinit secondary_star |
| struct mm_struct *mm = &init_mm; |
| unsigned int cpu = smp_processor_id(); |
| |
| - printk("CPU%u: Booted secondary processor\n", cpu); |
| - |
| /* |
| * All kernel threads share the same mm context; grab a |
| * reference and switch to it. |
| @@ -268,6 +266,8 @@ asmlinkage void __cpuinit secondary_star |
| enter_lazy_tlb(mm, current); |
| local_flush_tlb_all(); |
| |
| + printk("CPU%u: Booted secondary processor\n", cpu); |
| + |
| cpu_init(); |
| preempt_disable(); |
| trace_hardirqs_off(); |
