From: Colin Cross Date: Sat, 5 May 2012 19:58:13 +0000 (+0100) Subject: ARM: 7414/1: SMP: prevent use of the console when using idmap_pgd X-Git-Tag: v3.3.6~37 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c35fda8ad637d6f86fad00139f7faaf3d1133302;p=thirdparty%2Fkernel%2Fstable.git ARM: 7414/1: SMP: prevent use of the console when using idmap_pgd 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 Signed-off-by: Russell King Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index cdeb727527d39..31c256787d62a 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -255,8 +255,6 @@ 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. @@ -268,6 +266,8 @@ 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();