From fde165b2a29673aabf18ceff14dea1f1cfb0daad Mon Sep 17 00:00:00 2001 From: Colin Cross Date: Sat, 5 May 2012 20:58:13 +0100 Subject: [PATCH] ARM: 7414/1: SMP: prevent use of the console when using idmap_pgd 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. Cc: Signed-off-by: Colin Cross Signed-off-by: Russell King --- arch/arm/kernel/smp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index f6a4d32b0421..8f4644659777 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -251,8 +251,6 @@ asmlinkage void __cpuinit secondary_start_kernel(void) 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. @@ -264,6 +262,8 @@ asmlinkage void __cpuinit secondary_start_kernel(void) enter_lazy_tlb(mm, current); local_flush_tlb_all(); + printk("CPU%u: Booted secondary processor\n", cpu); + cpu_init(); preempt_disable(); trace_hardirqs_off(); -- GitLab