Re: [PATCH] bug in bigsmp CPU bringup

[Andrew Morton]

Len, Martin: please review?


From: "Pallipadi, Venkatesh" <venkatesh.pallipadi@xxxxxxxxx>

There is an bug in bigsmp sub-architecture, due to which it will not enable
all the CPUs when the BIOS-APICIDs are not 0 to n-1 (where n is total
number of CPUs).  Particularly, only 2 CPU comes up on a system that has 4
CPUs with BIOS APICID as (0, 1, 6, 7).

The bug is root caused to check_apicid_present(bit) call in smpboot.c, when
bigsmp is expecting apicid in place of bit.  check_apicid_present(bit) in
bigsmp subarchitecture checks the bit with phys_id_present_map (which is
actually map representing all apicids and not bit).

One solution is to change check_apicid_present(bit) to
check_apicid_present(apicid), in smp_boot_cpus().  But, it can affect all
the other subarchitectures in various subtle ways.  So, here is a simple
alternate fix (Thanks to Martin Bligh), which solves the above problem.


---

 25-akpm/include/asm-i386/mach-bigsmp/mach_apic.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletion(-)

diff -puN include/asm-i386/mach-bigsmp/mach_apic.h~bigsmp-cpu-bringup-fix include/asm-i386/mach-bigsmp/mach_apic.h
--- 25/include/asm-i386/mach-bigsmp/mach_apic.h~bigsmp-cpu-bringup-fix	2004-05-05 19:02:18.299905696 -0700
+++ 25-akpm/include/asm-i386/mach-bigsmp/mach_apic.h	2004-05-05 19:02:18.302905240 -0700
@@ -37,9 +37,10 @@ static inline unsigned long check_apicid
 	return 0;
 }
 
+/* we don't use the phys_cpu_present_map to indicate apicid presence */
 static inline unsigned long check_apicid_present(int bit) 
 {
-	return physid_isset(bit, phys_cpu_present_map);
+	return 1;
 }
 
 #define apicid_cluster(apicid) (apicid & 0xF0)

_

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