Initial import

ChibiOS_2.0.2/docs/src/atomic.dox

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+/*
+    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.
+
+    This file is part of ChibiOS/RT.
+
+    ChibiOS/RT is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    ChibiOS/RT is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+                                      ---
+
+    A special exception to the GPL can be applied should you wish to distribute
+    a combined work that includes ChibiOS/RT, without being obliged to provide
+    the source code for any proprietary components. See the file exception.txt
+    for full details of how and when the exception can be applied.
+*/
+
+/**
+ * @page article_atomic Invoking multiple primitives as a single atomic operation
+ * It is often necessary to invoke multiple operations involving a
+ * reschedule as a single atomic operation.<br>
+ * ChibiOS/RT already implements APIs that perform complex operations, as
+ * example the API @p chSemSignalWait() performs two operations atomically.<br>
+ * If more complex operations are required in your application then it is
+ * possible to build macro-operations, see the following example:
+ * @code
+  chSysLock();
+
+  chSemSignalI(&sem1);
+  chSemSignalI(&sem2);
+  chMtxUnlockS();
+  chSchRescheduleS();
+
+  chSysUnlock();
+ * @endcode
+ * The above example performs a signal operation on two semaphores, unlocks the
+ * last acquired mutex and finally performs a reschedule. All the operations
+ * are performed atomically.<br>
+ * An hypothetical @p chSemSignalSignalWait() operation could be implemented as
+ * follow:
+ * @code
+  chSysLock();
+
+  chSemSignalI(&sem1);
+  chSemSignalI(&sem2);
+  chSemWaitS(&Sem3);  /* May reschedule or not. */
+  chSchRescheduleS(); /* This one reschedules if necessary. */
+
+  chSysUnlock();
+ * @endcode
+ * In general multiple @ref I-Class and (non rescheduling) @ref S-Class APIs
+ * can be included and the block is terminated by a rescheduling @ref S-Class
+ * API. An extra @p chSchRescheduleS() can be present at the very end of the
+ * block, it only reschedules if a reschedule is still required.
+ */