[LinuxBIOS] PATCH: nested spinlock hang when initializing x86 sibling CPUs

[Steven J. Magnani]

This patch resolves the issue identified in
http://openbios.org/pipermail/linuxbios/2005-July/011903.html.

Changes:
* Remove spinlock bracketing of cpu_initialize() call
* Drop SERIAL_CPU_INIT option
* (Unrelated) Attempt more descriptive comments for various config
options

PATCH:

--- src/cpu/x86/lapic/lapic_cpu_init.c.orig	2005-09-09
09:29:25.156250000 -0500
+++ src/cpu/x86/lapic/lapic_cpu_init.c	2005-09-09 09:31:59.109375000
-0500
@@ -230,17 +230,16 @@
 void secondary_cpu_init(void)
 {
    atomic_inc(&active_cpus);
-#if SERIAL_CPU_INIT == 1
-  #if CONFIG_MAX_CPUS>2
-	spin_lock(&start_cpu_lock);
-  #endif
-#endif
+
+	// NOTE: The call to cpu_initialize() used to be bracketed by 
+	//       calls to lock and unlock the start_cpu_lock spin lock.
+	//       These were removed to resolve a hang due to nested spin
locking
+	//       when secondary CPUs go to initialize their siblings.
+	//       See
http://openbios.org/pipermail/linuxbios/2005-July/011903.html.
+	//       It's possible that some other form of concurrency
control 
+	//       is needed at this level.
    cpu_initialize();
-#if SERIAL_CPU_INIT == 1
-  #if CONFIG_MAX_CPUS>2
-	spin_unlock(&start_cpu_lock);
-  #endif
-#endif
+
    atomic_dec(&active_cpus);
    stop_this_cpu();
 }
@@ -265,11 +264,9 @@
    		printk_err("CPU  %u would not start!\n",
    			cpu->path.u.apic.apic_id);
    	}
-#if SERIAL_CPU_INIT == 1
   #if CONFIG_MAX_CPUS>2
    	udelay(10);
   #endif
-#endif
    }

/* Now loop until the other cpus have finished initializing */
--- src/config/Options.lb.orig	2005-09-09 09:36:27.562500000 -0500
+++ src/config/Options.lb	2005-09-09 09:35:17.125000000 -0500
@@ -188,37 +188,37 @@
    default 65536
    format "0x%x"
    export used
-	comment "Default fallback image size"
+	comment "ROM_SECTION_SIZE to use for the fallback build."
 end
 define ROM_SIZE
    default none
    format "0x%x"
    export used
-	comment "Size of your ROM"
+	comment "Total number of bytes allocated for normal and fallback
LinuxBIOS images and payloads. Note that the fallback image goes at the
end of the ROM, and the normal image at the beginning."
 end
 define ROM_IMAGE_SIZE
    default 65535
    format "0x%x"
    export always
-	comment "Default image size"
+	comment "Maximum number of bytes allowed for a LinuxBIOS image.
Does not include the payload."
 end
 define ROM_SECTION_SIZE
    default {FALLBACK_SIZE}
    format "0x%x"
    export used
-	comment "Default rom section size"
+	comment "Default rom section size. Normally, this is calculated
in mainboard Config.lb and varies between the normal and fallback
builds."
 end
 define ROM_SECTION_OFFSET
    default {ROM_SIZE - FALLBACK_SIZE}
    format "0x%x"
    export used
-	comment "Default rom section offset"
+	comment "Number of bytes from the beginning of the ROM to the
start of the section containing this build (normal or fallback).
Normally, this is calculated in mainboard Config.lb."
 end
 define PAYLOAD_SIZE
    default {ROM_SECTION_SIZE - ROM_IMAGE_SIZE}
    format "0x%x"
    export always
-	comment "Default payload size"
+	comment "Maximum number of bytes allowed for a payload.
Normally, this is calculated as above."
 end
 define _ROMBASE
    default {PAYLOAD_SIZE}
@@ -479,7 +479,7 @@
    export used
    comment "System clock frequency in MHz"
 end
-
+
 ###############################################
 # SMP options
 ###############################################
@@ -509,11 +509,6 @@
    export used
    comment "Define to build an MP table"
 end
-define SERIAL_CPU_INIT
-        default 1
-        export always
-        comment "Serialize CPU init"
-end

###############################################
 # Boot options
@@ -533,7 +528,7 @@
    default {0xffffffff - ROM_SIZE + ROM_SECTION_OFFSET + 1}
    format "0x%x"
    export always
-	comment "ROM stream start location"
+	comment "Memory address of this (normal or fallback) build's
payload in ROM. Normally, this is calculated as above."
 end
 define CONFIG_FS_STREAM
    default 0

--- src/mainboard/tyan/s2735/Options.lb.orig	2005-09-08
13:35:22.453125000 -0500
+++ src/mainboard/tyan/s2735/Options.lb	2005-09-09 09:21:21.531250000
-0500
@@ -8,7 +8,6 @@
 uses CONFIG_MAX_CPUS
 uses CONFIG_MAX_PHYSICAL_CPUS
 uses CONFIG_LOGICAL_CPUS
-uses SERIAL_CPU_INIT
 uses CONFIG_IOAPIC
 uses CONFIG_SMP
 uses FALLBACK_SIZE
@@ -127,8 +126,6 @@
 default CONFIG_MAX_PHYSICAL_CPUS=2
 default CONFIG_LOGICAL_CPUS=1

-default SERIAL_CPU_INIT=0
-
 #BTEXT Console
 #default CONFIG_CONSOLE_BTEXT=1

------------------------------------------------------------------------
 Steven J. Magnani               "I claim this network for MARS!
 www.digidescorp.com              Earthling, return my space modulator!"

#include <standard.disclaimer>