Commit 4ad8d383 authored by Zwane Mwaikambo's avatar Zwane Mwaikambo Committed by Linus Torvalds
Browse files

[PATCH] i386 boottime for_each_cpu broken 



for_each_cpu walks through all processors in cpu_possible_map, which is
defined as cpu_callout_map on i386 and isn't initialised until all
processors have been booted. This breaks things which do for_each_cpu
iterations early during boot. So, define cpu_possible_map as a bitmap with
NR_CPUS bits populated. This was triggered by a patch i'm working on which
does alloc_percpu before bringing up secondary processors.

From: Alexander Nyberg <alexn@telia.com>

i386-boottime-for_each_cpu-broken.patch
i386-boottime-for_each_cpu-broken-fix.patch

The SMP version of __alloc_percpu checks the cpu_possible_map before
allocating memory for a certain cpu.  With the above patches the BSP cpuid
is never set in cpu_possible_map which breaks CONFIG_SMP on uniprocessor
machines (as soon as someone tries to dereference something allocated via
__alloc_percpu, which in fact is never allocated since the cpu is not set
in cpu_possible_map).

Signed-off-by: default avatarZwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: default avatarAlexander Nyberg <alexn@telia.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent d7271b14

arch/i386/kernel/mpparse.c

+7 −1
Original line number Diff line number Diff line
@@ -122,7 +122,7 @@ static int MP_valid_apicid(int apicid, int version) 


static void __init MP_processor_info (struct mpc_config_processor *m)

{

 	int ver, apicid;

 	int ver, apicid, cpu, found_bsp = 0;

	physid_mask_t tmp;

 	

	if (!(m->mpc_cpuflag & CPU_ENABLED))
@@ -181,6 +181,7 @@ static void __init MP_processor_info (struct mpc_config_processor *m) 
	if (m->mpc_cpuflag & CPU_BOOTPROCESSOR) {

		Dprintk("    Bootup CPU\n");

		boot_cpu_physical_apicid = m->mpc_apicid;

		found_bsp = 1;

	}



	if (num_processors >= NR_CPUS) {
@@ -204,6 +205,11 @@ static void __init MP_processor_info (struct mpc_config_processor *m) 
		return;

	}



	if (found_bsp)

		cpu = 0;

	else

		cpu = num_processors - 1;

	cpu_set(cpu, cpu_possible_map);

	tmp = apicid_to_cpu_present(apicid);

	physids_or(phys_cpu_present_map, phys_cpu_present_map, tmp);

arch/i386/kernel/smpboot.c

+3 −0
Original line number Diff line number Diff line
@@ -88,6 +88,8 @@ EXPORT_SYMBOL(cpu_online_map); 
cpumask_t cpu_callin_map;

cpumask_t cpu_callout_map;

EXPORT_SYMBOL(cpu_callout_map);

cpumask_t cpu_possible_map;

EXPORT_SYMBOL(cpu_possible_map);

static cpumask_t smp_commenced_mask;



/* TSC's upper 32 bits can't be written in eariler CPU (before prescott), there
@@ -1265,6 +1267,7 @@ void __devinit smp_prepare_boot_cpu(void) 
	cpu_set(smp_processor_id(), cpu_online_map);

	cpu_set(smp_processor_id(), cpu_callout_map);

	cpu_set(smp_processor_id(), cpu_present_map);

	cpu_set(smp_processor_id(), cpu_possible_map);

	per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;

}

arch/i386/mach-voyager/voyager_smp.c

+3 −0
Original line number Diff line number Diff line
@@ -242,6 +242,8 @@ static cpumask_t smp_commenced_mask = CPU_MASK_NONE; 
cpumask_t cpu_callin_map = CPU_MASK_NONE;

cpumask_t cpu_callout_map = CPU_MASK_NONE;

EXPORT_SYMBOL(cpu_callout_map);

cpumask_t cpu_possible_map = CPU_MASK_ALL;

EXPORT_SYMBOL(cpu_possible_map);



/* The per processor IRQ masks (these are usually kept in sync) */

static __u16 vic_irq_mask[NR_CPUS] __cacheline_aligned;
@@ -1910,6 +1912,7 @@ void __devinit smp_prepare_boot_cpu(void) 
{

	cpu_set(smp_processor_id(), cpu_online_map);

	cpu_set(smp_processor_id(), cpu_callout_map);

	cpu_set(smp_processor_id(), cpu_possible_map);

}



int __devinit

include/asm-i386/smp.h

+1 −1
Original line number Diff line number Diff line
@@ -59,7 +59,7 @@ extern void cpu_uninit(void); 


extern cpumask_t cpu_callout_map;

extern cpumask_t cpu_callin_map;

#define cpu_possible_map cpu_callout_map

extern cpumask_t cpu_possible_map;



/* We don't mark CPUs online until __cpu_up(), so we need another measure */

static inline int num_booting_cpus(void)

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