[ 18/52] ARM: 7414/1: SMP: prevent use of the console when using idmap_pgd
From: Greg KH
Date: Thu May 10 2012 - 13:44:51 EST
3.3-stable review patch. If anyone has any objections, please let me know.
From: Colin Cross <ccross@xxxxxxxxxxx>
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@xxxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
arch/arm/kernel/smp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
@@ -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
+ printk("CPU%u: Booted secondary processor\n", cpu);
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