From: Don Zickus <dzickus@redhat.com>
Subject: Re: [RHEL-5 PATCH] enabling lockdep on x86_64 hangs the system
Date: Tue, 2 Jan 2007 17:40:51 -0500
Bugzilla: 221198
Message-Id: <20070102224051.GP5381@redhat.com>
Changelog: x86_64: enabling lockdep hangs the system


On Tue, Jan 02, 2007 at 05:33:45PM -0500, Don Zickus wrote:
> bugzilla: 221198
> 
> When we grabbed a bunch of stack unwinder fixes that when into 2.6.19,
> enabling lockdep on x86_64 caused boot problems.  We didn't care for
> awhile because we disabled lockdep (and also we couldn't figure out why).  
> 
> Cheers,
> Don
>


I think it was only needed for the printks and we can do them later.

I put in a single early_printk so that we know the kernel is alive
(early_printk doesn't need any locks)

This makes some things easier for initialization of unwind for
lockdep, which is needed by later patches.

cc: mingo@elte.hu

Signed-off-by: Andi Kleen <ak@suse.de>
---
 arch/x86_64/kernel/head64.c |    8 +-------
 arch/x86_64/kernel/setup.c  |    2 ++
 2 files changed, 3 insertions(+), 7 deletions(-)

Index: latest/arch/x86_64/kernel/head64.c
===================================================================
--- latest.orig/arch/x86_64/kernel/head64.c
+++ latest/arch/x86_64/kernel/head64.c
@@ -52,15 +52,12 @@ static void __init copy_bootdata(char *r
 	new_data = *(u32 *) (x86_boot_params + NEW_CL_POINTER);
 	if (!new_data) {
 		if (OLD_CL_MAGIC != *(u16 *)(real_mode_data + OLD_CL_MAGIC_ADDR)) {
-			printk("so old bootloader that it does not support commandline?!\n");
 			return;
 		}
 		new_data = __pa(real_mode_data) + *(u16 *)(real_mode_data + OLD_CL_OFFSET);
-		printk("old bootloader convention, maybe loadlin?\n");
 	}
 	command_line = __va(new_data);
 	memcpy(saved_command_line, command_line, COMMAND_LINE_SIZE);
-	printk("Bootdata ok (command line is %s)\n", saved_command_line);	
 }
 
 static void __init setup_boot_cpu_data(void)
@@ -95,10 +92,7 @@ void __init x86_64_start_kernel(char * r
 	/* Make NULL pointers segfault */
 	zap_identity_mappings();
 
-	/*
-	 * This must be called really, really early:
-	 */
-	lockdep_init();
+	early_printk("Kernel alive\n");
 
  	for (i = 0; i < NR_CPUS; i++)
  		cpu_pda(i) = &boot_cpu_pda[i];
Index: latest/arch/x86_64/kernel/setup.c
===================================================================
--- latest.orig/arch/x86_64/kernel/setup.c
+++ latest/arch/x86_64/kernel/setup.c
@@ -521,6 +521,8 @@ static void discover_ebda(void)
 
 void __init setup_arch(char **cmdline_p)
 {
+	printk(KERN_INFO "Command line: %s\n", saved_command_line);
+
  	ROOT_DEV = old_decode_dev(ORIG_ROOT_DEV);
  	screen_info = SCREEN_INFO;
 	edid_info = EDID_INFO;
Index: latest/arch/x86_64/kernel/mce.c
===================================================================
--- latest.orig/arch/x86_64/kernel/mce.c
+++ latest/arch/x86_64/kernel/mce.c
@@ -182,7 +182,7 @@ void do_machine_check(struct pt_regs * r
 		goto out2;
 
 	memset(&m, 0, sizeof(struct mce));
-	m.cpu = safe_smp_processor_id();
+	m.cpu = smp_processor_id();
 	rdmsrl(MSR_IA32_MCG_STATUS, m.mcgstatus);
 	if (!(m.mcgstatus & MCG_STATUS_RIPV))
 		kill_it = 1;
Index: latest/arch/x86_64/kernel/smp.c
===================================================================
--- latest.orig/arch/x86_64/kernel/smp.c
+++ latest/arch/x86_64/kernel/smp.c
@@ -521,27 +521,3 @@ asmlinkage void smp_call_function_interr
 		atomic_inc(&call_data->finished);
 	}
 }
-
-int safe_smp_processor_id(void)
-{
-	unsigned apicid, i;
-
-	if (disable_apic)
-		return 0;
-
-	apicid = hard_smp_processor_id();
-	if (apicid < NR_CPUS && x86_cpu_to_apicid[apicid] == apicid)
-		return apicid;
-
-	for (i = 0; i < NR_CPUS; ++i) {
-		if (x86_cpu_to_apicid[i] == apicid)
-			return i;
-	}
-
-	/* No entries in x86_cpu_to_apicid?  Either no MPS|ACPI,
-	 * or called too early.  Either way, we must be CPU 0. */
-      	if (x86_cpu_to_apicid[0] == BAD_APICID)
-		return 0;
-
-	return 0; /* Should not happen */
-}
Index: latest/arch/x86_64/kernel/traps.c
===================================================================
--- latest.orig/arch/x86_64/kernel/traps.c
+++ latest/arch/x86_64/kernel/traps.c
@@ -242,7 +242,7 @@ static unsigned long *in_exception_stack
 void dump_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * stack,
 		struct stacktrace_ops *ops, void *data)
 {
-	const unsigned cpu = safe_smp_processor_id();
+	const unsigned cpu = smp_processor_id();
 	unsigned long *irqstack_end = (unsigned long *)cpu_pda(cpu)->irqstackptr;
 	unsigned used = 0;
 
@@ -375,7 +375,7 @@ _show_stack(struct task_struct *tsk, str
 {
 	unsigned long *stack;
 	int i;
-	const int cpu = safe_smp_processor_id();
+	const int cpu = smp_processor_id();
 	unsigned long *irqstack_end = (unsigned long *) (cpu_pda(cpu)->irqstackptr);
 	unsigned long *irqstack = (unsigned long *) (cpu_pda(cpu)->irqstackptr - IRQSTACKSIZE);
 
@@ -429,7 +429,7 @@ void show_registers(struct pt_regs *regs
 	int i;
 	int in_kernel = !user_mode(regs);
 	unsigned long rsp;
-	const int cpu = safe_smp_processor_id(); 
+	const int cpu = smp_processor_id();
 	struct task_struct *cur = cpu_pda(cpu)->pcurrent;
 
 		rsp = regs->rsp;
@@ -504,7 +504,7 @@ static unsigned int die_nest_count;
 
 unsigned __kprobes long oops_begin(void)
 {
-	int cpu = safe_smp_processor_id();
+	int cpu = smp_processor_id();
 	unsigned long flags;
 
 	/* racy, but better than risking deadlock. */
@@ -582,7 +582,7 @@ void __kprobes die_nmi(char *str, struct
 	 * We are in trouble anyway, lets at least try
 	 * to get a message out.
 	 */
-	printk(str, safe_smp_processor_id());
+	printk(str, smp_processor_id());
 	show_registers(regs);
 	if (kexec_should_crash(current))
 		crash_kexec(regs);
Index: latest/include/asm-x86_64/smp.h
===================================================================
--- latest.orig/include/asm-x86_64/smp.h
+++ latest/include/asm-x86_64/smp.h
@@ -76,7 +76,6 @@ static inline int hard_smp_processor_id(
 	return GET_APIC_ID(*(unsigned int *)(APIC_BASE+APIC_ID));
 }
 
-extern int safe_smp_processor_id(void);
 extern int __cpu_disable(void);
 extern void __cpu_die(unsigned int cpu);
 extern void prefill_possible_map(void);
@@ -115,7 +114,6 @@ static inline int cpu_present_to_apicid(
 
 #ifndef CONFIG_SMP
 #define stack_smp_processor_id() 0
-#define safe_smp_processor_id() 0
 #define cpu_logical_map(x) (x)
 #else
 #include <asm/thread_info.h>
Index: latest/arch/x86_64/kernel/nmi.c
===================================================================
--- latest.orig/arch/x86_64/kernel/nmi.c
+++ latest/arch/x86_64/kernel/nmi.c
@@ -592,7 +592,7 @@ static nmi_callback_t nmi_callback = dum
  
 asmlinkage __kprobes void do_nmi(struct pt_regs * regs, long error_code)
 {
-	int cpu = safe_smp_processor_id();
+	int cpu = smp_processor_id();
 
 	nmi_enter();
 	add_pda(__nmi_count,1);