Changeset 25969ac in mainline

Timestamp:

2012-11-17T00:00:28Z (11 years ago)

Author:

Adam Hraska <adam.hraska+hos@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

089c23d

Parents:

853d613

Message:

smp_call: Comments clarifying memory semantics.

File:

• kernel/generic/src/smp/smp_call.c (modified) (3 diffs)

kernel/generic/src/smp/smp_call.c

@@ -69 +69 @@
  * directly.
  * 
+ * All memory accesses of prior to smp_call() will be visible
+ * to @a func on cpu @a cpu_id. Similarly, any changes @a func
+ * makes on cpu @a cpu_id will be visible on this cpu once
+ * smp_call() returns.
+ * 
+ * Invoking @a func on the destination cpu acts as a memory barrier
+ * on that cpu.
+ * 
  * @param cpu_id Destination CPU's logical id (eg CPU->id)
  * @param func Function to call.
@@ -89 +97 @@
  * @a func to complete.
  * 
- * @a call_info must be valid until @a func returns.
+ * @a call_info must be valid until/after @a func returns. Use
+ * smp_call_wait() to wait until it is safe to free @a call_info.
  * 
  * If @a cpu_id is the local CPU, the function will be invoked
  * directly. If the destination cpu id @a cpu_id is invalid
  * or denotes an inactive cpu, the call is discarded immediately.
+ * 
+ * All memory accesses of the caller prior to smp_call_async()
+ * will be made visible to @a func on the other cpu. Similarly, 
+ * any changes @a func makes on cpu @a cpu_id will be visible
+ * to this cpu when smp_call_wait() returns.
+ * 
+ * Invoking @a func on the destination cpu acts as a memory barrier
+ * on that cpu.
  * 
  * Interrupts must be enabled. Otherwise you run the risk
@@ -196 +213 @@
         list_initialize(&calls_list);
         
+        /* 
+         * Acts as a load memory barrier. Any changes made by the cpu that
+         * added the smp_call to calls_list will be made visible to this cpu.
+         */
         spinlock_lock(&CPU->smp_calls_lock);
         list_concat(&calls_list, &CPU->smp_pending_calls);