[PATCH 08/12] cpukit/libblock: No preempt handling in bdbuf init

[Ralf Kirchner]

Enabling and disabling preemption as done for single core will not work for SMP.
In the bdbuf initialization preemption handling can be avoided in general by using pthred_once().
---
 cpukit/libblock/src/bdbuf.c |   79 +++++++++++++++++++++++++++----------------
 1 Datei geändert, 49 Zeilen hinzugefügt(+), 30 Zeilen entfernt(-)

diff --git a/cpukit/libblock/src/bdbuf.c b/cpukit/libblock/src/bdbuf.c
index 07f479f..1e4887c 100644
--- a/cpukit/libblock/src/bdbuf.c
+++ b/cpukit/libblock/src/bdbuf.c
@@ -35,6 +35,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <inttypes.h>
+#include <pthread.h>
 
 #include <rtems.h>
 #include <rtems/error.h>
@@ -137,8 +138,6 @@ typedef struct rtems_bdbuf_cache
   rtems_id            read_ahead_task;   /**< Read-ahead task */
   rtems_chain_control read_ahead_chain;  /**< Read-ahead request chain */
   bool                read_ahead_enabled; /**< Read-ahead enabled */
-
-  bool                initialised;       /**< Initialised state. */
 } rtems_bdbuf_cache;
 
 typedef enum {
@@ -171,6 +170,20 @@ typedef enum {
   RTEMS_BDBUF_FATAL_WAIT_TRANS_EVNT
 } rtems_bdbuf_fatal_code;
 
+typedef struct {
+  pthread_once_t    is_initialized;
+  rtems_status_code return_status;
+} rtems_bdbuf_init_data_type;
+
+#define RTEMS_BDBUF_INIT_DATA_TYPE_INITIALIZER( \
+) \
+{ \
+  PTHREAD_ONCE_INIT, \
+  RTEMS_SUCCESSFUL \
+}
+
+static rtems_bdbuf_init_data_type rtems_bdbuf_data = RTEMS_BDBUF_INIT_DATA_TYPE_INITIALIZER();
+
 /**
  * The events used in this code. These should be system events rather than
  * application events.
@@ -1388,10 +1401,9 @@ rtems_bdbuf_read_request_size (uint32_t transfer_count)
 /**
  * Initialise the cache.
  *
- * @return rtems_status_code The initialisation status.
  */
-rtems_status_code
-rtems_bdbuf_init (void)
+static void
+rtems_bdbuf_init_once (void)
 {
   rtems_bdbuf_group*  group;
   rtems_bdbuf_buffer* bd;
@@ -1399,41 +1411,30 @@ rtems_bdbuf_init (void)
   size_t              b;
   size_t              cache_aligment;
   rtems_status_code   sc;
-  rtems_mode          prev_mode;
 
   if (rtems_bdbuf_tracer)
     printf ("bdbuf:init\n");
 
-  if (rtems_interrupt_is_in_progress())
-    return RTEMS_CALLED_FROM_ISR;
+  if (rtems_interrupt_is_in_progress()) {
+    rtems_bdbuf_data.return_status = RTEMS_CALLED_FROM_ISR;
+    goto end;
+  }
 
   /*
    * Check the configuration table values.
    */
 
-  if ((bdbuf_config.buffer_max % bdbuf_config.buffer_min) != 0)
-    return RTEMS_INVALID_NUMBER;
+  if ((bdbuf_config.buffer_max % bdbuf_config.buffer_min) != 0) {
+    rtems_bdbuf_data.return_status = RTEMS_INVALID_NUMBER;
+    goto end;
+  }
 
   if (rtems_bdbuf_read_request_size (bdbuf_config.max_read_ahead_blocks)
-      > RTEMS_MINIMUM_STACK_SIZE / 8U)
-    return RTEMS_INVALID_NUMBER;
-
-  /*
-   * We use a special variable to manage the initialisation incase we have
-   * completing threads doing this. You may get errors if the another thread
-   * makes a call and we have not finished initialisation.
-   */
-  prev_mode = rtems_bdbuf_disable_preemption ();
-  if (bdbuf_cache.initialised)
-  {
-    rtems_bdbuf_restore_preemption (prev_mode);
-    return RTEMS_RESOURCE_IN_USE;
+      > RTEMS_MINIMUM_STACK_SIZE / 8U) {
+    rtems_bdbuf_data.return_status = RTEMS_INVALID_NUMBER;
+    goto end;
   }
 
-  memset(&bdbuf_cache, 0, sizeof(bdbuf_cache));
-  bdbuf_cache.initialised = true;
-  rtems_bdbuf_restore_preemption (prev_mode);
-
   /*
    * For unspecified cache alignments we use the CPU alignment.
    */
@@ -1605,7 +1606,8 @@ rtems_bdbuf_init (void)
 
   rtems_bdbuf_unlock_cache ();
 
-  return RTEMS_SUCCESSFUL;
+  rtems_bdbuf_data.return_status = RTEMS_SUCCESSFUL;
+  goto end;
 
 error:
 
@@ -1650,9 +1652,26 @@ error:
     rtems_semaphore_delete (bdbuf_cache.lock);
   }
 
-  bdbuf_cache.initialised = false;
+  rtems_bdbuf_data.return_status = RTEMS_UNSATISFIED;
+
+end:;
+}
 
-  return RTEMS_UNSATISFIED;
+/**
+ * Initialise the cache.
+ *
+ * @return rtems_status_code The initialisation status.
+ */
+rtems_status_code
+rtems_bdbuf_init (void)
+{
+  int eno = pthread_once (&rtems_bdbuf_data.is_initialized, rtems_bdbuf_init_once);
+
+  if (eno != 0) {
+    return RTEMS_UNSATISFIED;
+  } else {
+    return rtems_bdbuf_data.return_status;
+  }
 }
 
 static void
-- 
1.7.10.4