[patch 15/22] alpha: SMP boot fixes

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-stable review patch.  If anyone has any objections, please let us know.


From: Brian Uhrain <[email protected]> says:

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 <[email protected]>

 - 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 <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Ivan Kokshaysky <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

 arch/alpha/kernel/setup.c |   17 +++++++++++++++++
 arch/alpha/kernel/smp.c   |    8 +++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

--- linux-
+++ linux-
@@ -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>
@@ -477,6 +478,22 @@ page_is_ram(unsigned long pfn)
 #undef PFN_PHYS
 #undef PFN_MAX
+static int __init
+	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;
 void __init
 setup_arch(char **cmdline_p)
--- linux-
+++ linux-
@@ -439,7 +439,7 @@ setup_smp(void)
 			if ((cpu->flags & 0x1cc) == 0x1cc) {
 				/* 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
-	 * 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);

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