Commit 917b1f78 authored Apr 10, 2006 by Brian Uhrain says Committed by Linus Torvalds Apr 11, 2006

[PATCH] alpha: SMP boot fixes



I've encountered two problems with 2.6.16 and newer kernels on my API CS20
(dual 833MHz Alpha 21264b processors).  The first is the kernel OOPSing
because of a NULL pointer dereference while trying to populate SysFS with the
CPU information.  The other is that only one processor was being brought up.
I've included a small Alpha-specific patch that fixes both problems.

The first problem was caused by the CPUs never being properly registered using
register_cpu(), the way it's done on other architectures.

The second problem has to do with the removal of hwrpb_cpu_present_mask in
arch/alpha/kernel/smp.c.  In setup_smp() in the 2.6.15 kernel sources,
hwrpb_cpu_present_mask has a bit set for each processor that is probed, and
afterwards cpu_present_mask is set to the cpumask for the boot CPU.  In the
same function of the same file in the 2.6.16 sources, instead of
hwrpb_cpu_present_mask being set, cpu_possible_map is updated for each probed
CPU.  cpu_present_mask is still set to the cpumask of the boot CPU afterwards.
 The problem lies in include/asm-alpha/smp.h, where cpu_possible_map is
#define'd to be cpu_present_mask.

Cleanups from: Ivan Kokshaysky <ink@jurassic.park.msu.ru>

 - cpu_present_mask and cpu_possible_map are essentially the same thing
   on alpha, as it doesn't support CPU hotplug;
 - allocate "struct cpu" only for present CPUs, like sparc64 does.
   Static array of "struct cpu" is just a waste of memory.

Signed-off-by: Brian Uhrain <buhrain@rosettastone.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 1c08ca89

arch/alpha/kernel/setup.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -24,6 +24,7 @@
		#include <linux/config.h> /* CONFIG_ALPHA_LCA etc */
		#include <linux/mc146818rtc.h>
		#include <linux/console.h>
		#include <linux/cpu.h>
		#include <linux/errno.h>
		#include <linux/init.h>
		#include <linux/string.h>
		@@ -471,6 +472,22 @@ page_is_ram(unsigned long pfn)
		return 0;
		}

		static int __init
		register_cpus(void)
		{
		int i;

		for_each_possible_cpu(i) {
		struct cpu p = kzalloc(sizeof(p), GFP_KERNEL);
		if (!p)
		return -ENOMEM;
		register_cpu(p, i, NULL);
		}
		return 0;
		}

		arch_initcall(register_cpus);

		void __init
		setup_arch(char **cmdline_p)
		{

arch/alpha/kernel/smp.c

+3 −5

Original line number	Diff line number	Diff line
		@@ -439,7 +439,7 @@ setup_smp(void)
		if ((cpu->flags & 0x1cc) == 0x1cc) {
		smp_num_probed++;
		/* Assume here that "whami" == index */
		cpu_set(i, cpu_possible_map);
		cpu_set(i, cpu_present_mask);
		cpu->pal_revision = boot_cpu_palrev;
		}

		@@ -450,9 +450,8 @@ setup_smp(void)
		}
		} else {
		smp_num_probed = 1;
		cpu_set(boot_cpuid, cpu_possible_map);
		cpu_set(boot_cpuid, cpu_present_mask);
		}
		cpu_present_mask = cpumask_of_cpu(boot_cpuid);

		printk(KERN_INFO "SMP: %d CPUs probed -- cpu_present_mask = %lx\n",
		smp_num_probed, cpu_possible_map.bits[0]);
		@@ -488,9 +487,8 @@ void __devinit
		smp_prepare_boot_cpu(void)
		{
		/*
		* Mark the boot cpu (current cpu) as both present and online
		* Mark the boot cpu (current cpu) as online
		*/
		cpu_set(smp_processor_id(), cpu_present_mask);
		cpu_set(smp_processor_id(), cpu_online_map);
		}