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* Revert r42319 as it introduces a race condition when entering the kernel 

debugger. As sInDebugger is already > 0 when the first CPU enters KDL, code
  from other CPUs might see debug_debugger_running() == true already before they
  enter the debugger.
* Instead, move the sDebuggerOnCPU setting out of the debugger loop and hold the
  value until after calling exit_kernel_debugger() so that the exit hooks still
  see debug_debugger_running() == true.
* Also avoid calling exit_kernel_debugger() when we've been called recursively
  (previousCPU != -1). Previously the exit hooks would've been called and the
  debugger state reset erroneously. To balance the missing decrement of
  sInDebugger in that case we decrement sInDebugger in enter_kernel_debugger()
  also when detecting the recursion case.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42320 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Michael Lotz 2011-06-26 00:06:52 +00:00
parent 3214710036
commit 14c345e147
1 changed files with 15 additions and 9 deletions
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24
src/system/kernel/debug/debug.cpp
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@ -805,9 +805,6 @@ static void
kernel_debugger_loop(const char* messagePrefix, const char* message,
va_list args, int32 cpu)
{
int32 previousCPU = sDebuggerOnCPU;
sDebuggerOnCPU = cpu;
DebugAllocPool* allocPool = create_debug_alloc_pool();
sCurrentKernelDebuggerMessagePrefix = messagePrefix;
@ -936,8 +933,6 @@ kernel_debugger_loop(const char* messagePrefix, const char* message,
va_end(sCurrentKernelDebuggerMessageArgs);
delete_debug_alloc_pool(allocPool);
sDebuggerOnCPU = previousCPU;
}
@ -945,6 +940,8 @@ static void
enter_kernel_debugger(int32 cpu)
{
while (atomic_add(&sInDebugger, 1) > 0) {
atomic_add(&sInDebugger, -1);
// The debugger is already running, find out where...
if (sDebuggerOnCPU == cpu) {
// We are re-entering the debugger on the same CPU.
@ -955,7 +952,6 @@ enter_kernel_debugger(int32 cpu)
// us. Process ICIs to ensure we get the halt request. Then we are
// blocking there until everyone leaves the debugger and we can
// try to enter it again.
atomic_add(&sInDebugger, -1);
smp_intercpu_int_handler(cpu);
}
@ -1027,13 +1023,23 @@ kernel_debugger_internal(const char* messagePrefix, const char* message,
} else
enter_kernel_debugger(cpu);
// If we're called recursively sDebuggerOnCPU will be != -1.
int32 previousCPU = sDebuggerOnCPU;
sDebuggerOnCPU = cpu;
kernel_debugger_loop(messagePrefix, message, args, cpu);
if (sHandOverKDLToCPU < 0) {
if (sHandOverKDLToCPU < 0 && previousCPU == -1) {
// We're not handing over to a different CPU and we weren't
// called recursively, so we'll exit the debugger.
exit_kernel_debugger();
break;
}
sDebuggerOnCPU = previousCPU;
if (sHandOverKDLToCPU < 0)
break;
hand_over_kernel_debugger();
debug_trap_cpu_in_kdl(cpu, true);
@ -1617,7 +1623,7 @@ debug_stop_screen_debug_output(void)
bool
debug_debugger_running(void)
{
return sInDebugger > 0;
return sDebuggerOnCPU != -1;
}