score: Rework idle handling in SMP schedulers

This patch fixes an issue with the idle thread handling in the SMP
scheduler framework used for the MrsP locking protocol.  The approach to
use a simple chain of unused idle threads is broken for schedulers which
support thread to processor affinity.  The reason is that the thread to
processor affinity introduces another ordering indicator which may under
certain conditions lead to a reordering of idle threads in the scheduled
chain.  This reordering is not propagated to the chain of unused idle
threads.  This could lead to use an idle thread for a sticky scheduler
node which is already in use.  This locks up the system in infinite
loops in the thread context switch procedure.

To fix this, the SMP scheduler implementations must now provide
callbacks to get and release an unused idle thread.

Update #4531.

1 files changed, 1 insertions, 0 deletions

diff --git a/cpukit/include/rtems/score/schedulerprioritysmp.h b/cpukit/include/rtems/score/schedulerprioritysmp.h
index 9ece9ae143..21916647bc 100644
--- a/cpukit/include/rtems/score/schedulerprioritysmp.h
+++ b/cpukit/include/rtems/score/schedulerprioritysmp.h
@@ -57,6 +57,7 @@ extern "C" {
  */
 typedef struct {
   Scheduler_SMP_Context    Base;
+  Chain_Control           *idle_ready_queue;
   Priority_bit_map_Control Bit_map;
   Chain_Control            Ready[ RTEMS_ZERO_LENGTH_ARRAY ];
 } Scheduler_priority_SMP_Context;