[PATCH][x86_64] IPI calltraces on x86_64

[Kirill Korotaev <dev@openvz.org>]

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[PATCH] IPI calltraces on x86_64

This patch makes x86_64 kernel to print calltraces on _all_
CPUs on Alt-SysRq-p and NMI LOCKUP.
This patch supplements the one made for i386
some time ago and included in -mm tree.
Since it proved its usefullness many times already
we did the same patch for x86_64.

Signed-Off-By: Pavel Emelianov <xemul@openvz.org>
Signed-Off-By: Kirill Korotaev <dev@openvz.org>

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--- ./arch/x86_64/kernel/nmi.c.ve129	2006-03-20 08:53:29.000000000 +0300
+++ ./arch/x86_64/kernel/nmi.c	2006-04-05 17:35:49.000000000 +0400
@@ -522,6 +522,7 @@ static __kprobes int dummy_nmi_callback(
 }
  
 static nmi_callback_t nmi_callback = dummy_nmi_callback;
+static nmi_callback_t nmi_ipi_callback = dummy_nmi_callback;
  
 asmlinkage __kprobes void do_nmi(struct pt_regs * regs, long error_code)
 {
@@ -531,9 +532,21 @@ asmlinkage __kprobes void do_nmi(struct 
 	add_pda(__nmi_count,1);
 	if (!rcu_dereference(nmi_callback)(regs, cpu))
 		default_do_nmi(regs);
+
+	nmi_ipi_callback(regs, cpu);
 	nmi_exit();
 }
 
+void set_nmi_ipi_callback(nmi_callback_t callback)
+{
+	nmi_ipi_callback = callback;
+}
+
+void unset_nmi_ipi_callback(void)
+{
+	nmi_ipi_callback = dummy_nmi_callback;
+}
+
 void set_nmi_callback(nmi_callback_t callback)
 {
 	rcu_assign_pointer(nmi_callback, callback);
--- ./arch/x86_64/kernel/process.c.ve129	2006-04-05 16:52:55.000000000 +0400
+++ ./arch/x86_64/kernel/process.c	2006-04-05 18:13:16.000000000 +0400
@@ -345,6 +345,21 @@ void show_regs(struct pt_regs *regs)
 	show_trace(&regs->rsp);
 }
 
+void smp_show_regs(struct pt_regs *regs, void *data)
+{
+	static DEFINE_SPINLOCK(show_regs_lock);
+
+	if (regs == NULL)
+		return;
+
+	bust_spinlocks(1);
+	spin_lock(&show_regs_lock);
+	printk("----------- IPI show regs -----------\n");
+	show_regs(regs);
+	spin_unlock(&show_regs_lock);
+	bust_spinlocks(0);
+}
+
 /*
  * Free current thread data structures etc..
  */
--- ./arch/x86_64/kernel/smp.c.ve129	2006-04-05 15:11:18.000000000 +0400
+++ ./arch/x86_64/kernel/smp.c	2006-04-05 18:15:30.000000000 +0400
@@ -28,6 +28,7 @@
 #include <asm/proto.h>
 #include <asm/apicdef.h>
 #include <asm/idle.h>
+#include <asm/nmi.h>
 
 /*
  *	Smarter SMP flushing macros. 
@@ -444,6 +445,84 @@ int smp_call_function (void (*func) (voi
 	return 0;
 }
 
+static spinlock_t nmi_call_lock = SPIN_LOCK_UNLOCKED;
+static struct nmi_call_data_struct {
+	smp_nmi_function func;
+	void *info;
+	atomic_t started;
+	atomic_t finished;
+	cpumask_t cpus_called;
+	int wait;
+} *nmi_call_data;
+
+static int smp_nmi_callback(struct pt_regs * regs, int cpu)
+{
+	smp_nmi_function func;
+	void *info;
+	int wait;
+
+	func = nmi_call_data->func;
+	info = nmi_call_data->info;
+	wait = nmi_call_data->wait;
+	ack_APIC_irq();
+	/* prevent from calling func() multiple times */
+	if (cpu_test_and_set(cpu, nmi_call_data->cpus_called))
+		return 0;
+	/*
+	 * notify initiating CPU that I've grabbed the data and am
+	 * about to execute the function
+	 */
+	mb();
+	atomic_inc(&nmi_call_data->started);
+	/* at this point the nmi_call_data structure is out of scope */
+	irq_enter();
+	func(regs, info);
+	irq_exit();
+	if (wait)
+		atomic_inc(&nmi_call_data->finished);
+
+	return 0;
+}
+
+int smp_nmi_call_function(smp_nmi_function func, void *info, int wait)
+{
+	struct nmi_call_data_struct data;
+	int cpus;
+
+	cpus = num_online_cpus() - 1;
+	if (!cpus)
+		return 0;
+
+	data.func = func;
+	data.info = info;
+	data.wait = wait;
+	atomic_set(&data.started, 0);
+	atomic_set(&data.finished, 0);
+	cpus_clear(data.cpus_called);
+	/* prevent this cpu from calling func if NMI happens */
+	cpu_set(smp_processor_id(), data.cpus_called);
+
+	if (!spin_trylock(&nmi_call_lock))
+		return -1;
+
+	nmi_call_data = &data;
+	set_nmi_ipi_callback(smp_nmi_callback);
+	mb();
+
+	/* Send a message to all other CPUs and wait for them to respond */
+	send_IPI_allbutself(APIC_DM_NMI);
+	while (atomic_read(&data.started) != cpus)
+		barrier();
+
+	unset_nmi_ipi_callback();
+	if (wait)
+		while (atomic_read(&data.finished) != cpus)
+			barrier();
+	spin_unlock(&nmi_call_lock);
+
+	return 0;
+}
+
 void smp_stop_cpu(void)
 {
 	unsigned long flags;
--- ./arch/x86_64/kernel/traps.c.ve129	2006-04-05 16:52:55.000000000 +0400
+++ ./arch/x86_64/kernel/traps.c	2006-04-05 17:43:53.000000000 +0400
@@ -460,6 +460,7 @@ void __kprobes die_nmi(char *str, struct
 	show_registers(regs);
 	if (panic_on_timeout || panic_on_oops)
 		panic("nmi watchdog");
+	smp_nmi_call_function(smp_show_regs, NULL, 1);
 	printk("console shuts up ...\n");
 	oops_end(flags);
 	do_exit(SIGSEGV);
--- ./drivers/char/sysrq.c.ve129	2006-04-05 16:52:55.000000000 +0400
+++ ./drivers/char/sysrq.c	2006-04-05 17:55:06.000000000 +0400
@@ -178,7 +178,7 @@ static void sysrq_handle_showregs(int ke
 	if (pt_regs)
 		show_regs(pt_regs);
 	bust_spinlocks(0);
-#ifdef __i386__
+#if defined(__i386__) || defined(__x86_64__)
 	smp_nmi_call_function(smp_show_regs, NULL, 0);
 #endif
 }
--- ./include/asm-x86_64/nmi.h.ve129	2006-03-20 08:53:29.000000000 +0300
+++ ./include/asm-x86_64/nmi.h	2006-04-05 17:44:44.000000000 +0400
@@ -24,6 +24,9 @@ void set_nmi_callback(nmi_callback_t cal
  * Remove the handler previously set.
  */
 void unset_nmi_callback(void);
+
+void set_nmi_ipi_callback(nmi_callback_t callback);
+void unset_nmi_ipi_callback(void);
  
 #ifdef CONFIG_PM