kernel/debug: Introduce arch_debug_snooze() and make use of it.

The idea is to add a facility that will use less CPU than
the loops we currently use. The default implementation just
calls spin(), which is rdtsc+pause. This already may save
some power compared to what we previously did, which was to
re-check serial ports, PS/2, etc. every single loop in
the debugger, broken up only by "pause".

Change-Id: Ie421adae5c25ad6ae0c266d1d28c2ea7b81ae465
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9603
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>

headers/private/kernel/arch/debug.h

@@ -53,6 +53,8 @@ status_t arch_get_debug_variable(const char* variableName, uint64* value);
 
 ssize_t arch_debug_gdb_get_registers(char* buffer, size_t bufferSize);
 
+void arch_debug_snooze(bigtime_t duration);
+
 #ifdef __cplusplus
 }
 #endif

src/system/kernel/arch/arm/arch_debug.cpp

@@ -502,6 +502,13 @@ arch_get_debug_variable(const char* variableName, uint64* value)
 }
 
 
+void
+arch_debug_snooze(bigtime_t duration)
+{
+	spin(duration);
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/arch/arm64/arch_debug.cpp

@@ -479,6 +479,13 @@ arch_get_debug_variable(const char* variableName, uint64* value)
 }
 
 
+void
+arch_debug_snooze(bigtime_t duration)
+{
+	spin(duration);
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/arch/m68k/arch_debug.cpp

@@ -393,6 +393,13 @@ arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
 }
 
 
+void
+arch_debug_snooze(bigtime_t duration)
+{
+	spin(duration);
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/arch/ppc/arch_debug.cpp

@@ -336,6 +336,13 @@ arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
 }
 
 
+void
+arch_debug_snooze(bigtime_t duration)
+{
+	spin(duration);
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/arch/riscv64/arch_debug.cpp

@@ -1136,11 +1136,16 @@ arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
 }
 
 
+void
+arch_debug_snooze(bigtime_t duration)
+{
+	spin(duration);
+}
+
+
 status_t
 arch_debug_init(kernel_args* args)
 {
-	// at this stage, the debugger command system is alive
-
 	add_debugger_command("where", &stack_trace, "Same as \"sc\"");
 	add_debugger_command("bt", &stack_trace, "Same as \"sc\" (as in gdb)");
 	add_debugger_command("sc", &stack_trace,

src/system/kernel/arch/sparc/arch_debug.cpp

@@ -92,6 +92,13 @@ arch_debug_get_interrupt_pc(bool* _isSyscall)
 }
 
 
+void
+arch_debug_snooze(bigtime_t duration)
+{
+	spin(duration);
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/arch/x86/arch_debug.cpp

@@ -1357,6 +1357,13 @@ arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
 }
 
 
+void
+arch_debug_snooze(bigtime_t duration)
+{
+	spin(duration);
+}
+
+
 status_t
 arch_debug_init(kernel_args* args)
 {

src/system/kernel/debug/debug.cpp

@@ -715,7 +715,7 @@ kgetc(void)
 			}
 		}
 
-		cpu_pause();
+		arch_debug_snooze(5000);
 	}
 }
 
@@ -1824,7 +1824,7 @@ debug_trap_cpu_in_kdl(int32 cpu, bool returnIfHandedOver)
 	sCPUTrapped[cpu] = true;
 
 	while (sInDebugger != 0) {
-		cpu_pause();
+		arch_debug_snooze(10000);
 
 		if (sHandOverKDL && sHandOverKDLToCPU == cpu) {
 			if (returnIfHandedOver)