smp: Simplify SMP initialization sequence

Delete bsp_smp_wait_for().  Other parts of the system work without
timeout, e.g. the spinlocks.  Using a timeout here does not make the
system more robust.

Delete bsp_smp_cpu_state and replace it with Per_CPU_State.  The
Per_CPU_State follows the Score naming conventions.  Add
_Per_CPU_Change_state() and _Per_CPU_Wait_for_state() functions to
change and observe states.

Use Per_CPU_State in Per_CPU_Control instead of the anonymous integer.

Add _CPU_Processor_event_broadcast() and _CPU_Processor_event_receive()
functions provided by the CPU port.  Use these functions in
_Per_CPU_Change_state() and _Per_CPU_Wait_for_state().

Add prototype for _SMP_Send_message().

Delete RTEMS_BSP_SMP_FIRST_TASK message.  The first context switch is
now performed in rtems_smp_secondary_cpu_initialize().  Issuing the
first context switch in the context of the inter-processor interrupt is
not possible on systems with a modern interrupt controller.  Such an
interrupt controler usually requires a handshake protocol with interrupt
acknowledge and end of interrupt signals.  A direct context switch in an
interrupt handler circumvents the interrupt processing epilogue and may
leave the system in an inconsistent state.

Release lock in rtems_smp_process_interrupt() even if no message was
delivered.  This prevents deadlock of the system.

Simplify and format _SMP_Send_message(),
_SMP_Request_other_cores_to_perform_first_context_switch(),
_SMP_Request_other_cores_to_dispatch() and
_SMP_Request_other_cores_to_shutdown().

1 files changed, 26 insertions, 3 deletions

diff --git a/cpukit/score/src/percpu.c b/cpukit/score/src/percpu.c
index f01d933cfe..a957053e18 100644
--- a/cpukit/score/src/percpu.c
+++ b/cpukit/score/src/percpu.c
@@ -56,9 +56,6 @@
         p->interrupt_stack_high = (void *)ptr;
       }
 #endif
-
-      p->state = RTEMS_BSP_SMP_CPU_INITIAL_STATE;
-      RTEMS_COMPILER_MEMORY_BARRIER();
     }
 
     /*
@@ -67,6 +64,32 @@
     max_cpus = bsp_smp_initialize( max_cpus );
 
     _SMP_Processor_count = max_cpus;
+
+    for ( cpu = 1 ; cpu < max_cpus; ++cpu ) {
+      _Per_CPU_Wait_for_state(
+        &_Per_CPU_Information[ cpu ],
+        PER_CPU_STATE_READY_TO_BEGIN_MULTITASKING
+      );
+    }
+  }
+
+  void _Per_CPU_Change_state(
+    Per_CPU_Control *per_cpu,
+    Per_CPU_State new_state
+  )
+  {
+    per_cpu->state = new_state;
+    _CPU_Processor_event_broadcast();
+  }
+
+  void _Per_CPU_Wait_for_state(
+    const Per_CPU_Control *per_cpu,
+    Per_CPU_State desired_state
+  )
+  {
+    while ( per_cpu->state != desired_state ) {
+      _CPU_Processor_event_receive();
+    }
   }
 #else
   /*