From 48b0c6f93ad3ba41103e59e3008b8ac6247e8f28 Mon Sep 17 00:00:00 2001
From: Ingo Weinhold <ingo_weinhold@gmx.de>
Date: Thu, 16 Apr 2009 21:55:40 +0000
Subject: [PATCH] debug_trap_cpu_in_kdl(): If the CPU running the kernel
 debugger exited and re-entered it fast enough, we wouldn't leave the loop and
 thus cause a deadlock, since we wouldn't process the ICI message telling us
 to halt. We do now call smp_intercpu_int_handler() in the loop and guard the
 function from being re-entered. This also has the advantage that we can
 execute code on all CPUs in the kernel debugger, if we have to.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@30208 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 src/system/kernel/debug/debug.cpp | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/system/kernel/debug/debug.cpp b/src/system/kernel/debug/debug.cpp
index 92ba0579a0..83bcafc0d5 100644
--- a/src/system/kernel/debug/debug.cpp
+++ b/src/system/kernel/debug/debug.cpp
@@ -26,6 +26,7 @@
 
 #include <arch/debug_console.h>
 #include <arch/debug.h>
+#include <util/AutoLock.h>
 #include <util/ring_buffer.h>
 
 #include <syslog_daemon.h>
@@ -102,6 +103,8 @@ static vint32 sInDebugger = 0;
 static bool sPreviousDprintfState;
 static volatile bool sHandOverKDL = false;
 static vint32 sHandOverKDLToCPU = -1;
+static bool sCPUTrapped[B_MAX_CPU_COUNT];
+
 
 #define distance(a, b) ((a) < (b) ? (b) - (a) : (a) - (b))
 
@@ -1307,19 +1310,28 @@ debug_get_page_fault_info()
 void
 debug_trap_cpu_in_kdl(bool returnIfHandedOver)
 {
-	cpu_status state = disable_interrupts();
+	InterruptsLocker locker;
+
+	int cpu = smp_get_current_cpu();
+
+	// return, if we've been called recursively (we call
+	// smp_intercpu_int_handler() below)
+	if (sCPUTrapped[cpu])
+		return;
+
+	sCPUTrapped[cpu] = true;
 
 	while (sInDebugger != 0) {
-		if (sHandOverKDL && sHandOverKDLToCPU == smp_get_current_cpu()) {
+		if (sHandOverKDL && sHandOverKDLToCPU == cpu) {
 			if (returnIfHandedOver)
-				return;
+				break;
 
 			kernel_debugger(NULL);
 		} else
-			PAUSE();
+			smp_intercpu_int_handler();
 	}
 
-	restore_interrupts(state);
+	sCPUTrapped[cpu] = false;
 }