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x86: make pda a percpu variable

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[ Based on original patch from Christoph Lameter and Mike Travis. ]

As pda is now allocated in percpu area, it can easily be made a proper
percpu variable.  Make it so by defining per cpu symbol from linker
script and declaring it in C code for SMP and simply defining it for
UP.  This change cleans up code and brings SMP and UP closer a bit.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Tejun Heo
2009-01-13 20:41:35 +09:00
committed by Ingo Molnar
parent 9939ddaff5
commit b12d8db8fb
6 changed files with 23 additions and 20 deletions
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16
arch/x86/kernel/setup_percpu.c
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@@ -66,6 +66,16 @@ static void __init setup_node_to_cpumask_map(void);
static inline void setup_node_to_cpumask_map(void) { }
#endif
/*
* Define load_pda_offset() and per-cpu __pda for x86_64.
* load_pda_offset() is responsible for loading the offset of pda into
* %gs.
*
* On SMP, pda offset also duals as percpu base address and thus it
* should be at the start of per-cpu area. To achieve this, it's
* preallocated in vmlinux_64.lds.S directly instead of using
* DEFINE_PER_CPU().
*/
#ifdef CONFIG_X86_64
void __cpuinit load_pda_offset(int cpu)
{
@@ -74,6 +84,10 @@ void __cpuinit load_pda_offset(int cpu)
wrmsrl(MSR_GS_BASE, cpu_pda(cpu));
mb();
}
#ifndef CONFIG_SMP
DEFINE_PER_CPU(struct x8664_pda, __pda);
EXPORT_PER_CPU_SYMBOL(__pda);
#endif
#endif /* CONFIG_SMP && CONFIG_X86_64 */
@@ -180,8 +194,6 @@ void __init setup_per_cpu_areas(void)
memcpy(ptr, __per_cpu_load, __per_cpu_end - __per_cpu_start);
per_cpu_offset(cpu) = ptr - __per_cpu_start;
#ifdef CONFIG_X86_64
cpu_pda(cpu) = (void *)ptr;
/*
* CPU0 modified pda in the init data area, reload pda
* offset for CPU0 and clear the area for others.