task: Add task_set_essential

Whenever a Hurd essential task crashes, startup just reboots the system
since there's not much that can be done at that point. When we have a
kernel debugger, however, we could at least get crashing information, so
let's let Hurd's startup tell the kernel which tasks are essential, and
trigger the debugger whenever they crash.

1 files changed, 11 insertions, 0 deletions

diff --git a/doc/mach.texi b/doc/mach.texi
index 4abafe1a..fecd097b 100644
--- a/doc/mach.texi
+++ b/doc/mach.texi
@@ -5100,6 +5100,17 @@ printed by the kernel.
 The function returns @code{KERN_SUCCESS} if the call succeeded.
 @end deftypefun
 
+@deftypefun kern_return_t task_set_essential (@w{task_t @var{target_task}}, @w{boolean_t @var{essential}})
+
+The function @code{task_set_essential} sets whether @var{target_task} is
+essential for the system, i.e. the system will completely crash and reboot if
+that task crashes. This means that when the debugger is enabled, it should be
+triggered on the crash, so as to get the opportunity to debug the issue instead
+of just rebooting.
+
+The function returns @code{KERN_SUCCESS} if the call succeeded.
+@end deftypefun
+
 
 @node Task Execution
 @subsection Task Execution