Changes between Version 39 and Version 40 of Language

Timestamp:

05/21/23 13:42:01 (3 years ago)

Author:

siegel

Comment:

--

Language

@@ -294 +294 @@
 == Statements #statements
 
-=== Atomic blocks: `$atomic` #atomic
-
-An ''atomic block'' has syntax
-  `$atomic` `{` ( ''stmt'' ( `,` stmt )* )? `}`
+=== Atomic statements: `$atomic` #atomic
+
+An atomic statement has syntax
+  `$atomic` ''stmt''
+It indicates that ''stmt'' should be executed without the intervention of other processes.
 For example,
 {{{
@@ -305 +306 @@
 }
 }}}
-It indicates that the statements comprising the block should be executed without the intervention of other processes.
-
-More precisely, there is a global atomic lock which is initially free.
-A process attempting to execute an atomic block will wait until the atomic lock becomes free, i.e., no other process is inside an atomic block.
-The process must also wait until the guard of the atomic block holds; this means that the first statement in the block is enabled.
-Once the atomic lock is free and the guard holds, the atomic block becomes enabled and the process may enter the atomic block.
-The process may not necessarily enter the atomic block as soon as these conditions hold, because some other enabled process may be scheduled first.
+In this example, ''stmt'' is a compound statement `{` ... `}`.  This is usually the case.
+
+Semantics: there is a global atomic lock which is initially free.
+A process attempting to execute an atomic statement will wait until the atomic lock becomes free, i.e., no other process is inside an atomic statement.
+The process must also wait until the guard of the atomic statement holds; this means that the first sub-statement of the statement is enabled.
+Once the atomic lock is free and the guard holds, the atomic statement becomes enabled and the process may enter the atomic statement.
+The process may not necessarily enter the atomic statement as soon as these conditions hold, because some other enabled process may be scheduled first.
 In fact, some other process may obtain the atomic lock.
-But if the enabling conditions hold and this process is scheduled, it will obtain the atomic lock and begin executing the statements
-of the atomic block without other processes executing.
-Upon reaching the end of the atomic block, the process releases the atomic lock and exits the block.
-
-There is an exception to atomicity: if the process inside the atomic block executes a [#yield $yield statement], it releases the atomic lock.
+But if the enabling conditions hold and this process is scheduled, it will obtain the atomic lock and begin executing ''stmt'' without other processes executing.
+Upon reaching the end of ''stmt'', the process releases the atomic lock and exits ''stmt''.
+
+There is an exception to atomicity: if the process executing inside the atomic statement call the [#yield $yield function], it releases the atomic lock.
 This allows other processes to execute, and even obtain the lock.
 At any point at which the atomic lock is free and the first statement following the `$yield` is enabled, the original process may re-obtain
-the atomic lock and continue executing its block atomically.
-
-If a statement inside an atomic block blocks, so that the process executing the atomic block has no enabled statement, execution deadlocks. 
-The exception to this rule is that the first statement in the atomic block, and the first statement after a `$yield`, as described above,
+the atomic lock and continue executing atomically.
+
+If a statement inside an atomic statement blocks, so that the process executing the atomic statement has no enabled statement, execution deadlocks. 
+The exception to this rule is that the first sub-statement in the atomic statement, and the first statement after a `$yield`, as described above,
 may block, without necessarily causing deadlock.
 
@@ -331 +331 @@
 These counters are initially 0.
 When a process acquires the lock, the counter is set to 1.
-Each time the process attempts to enter an atomic block when it already owns the lock, it succeeds immediately and the counter is incremented.
-Each time the process leaves an atomic block, the counter is decremented.
+Each time the process attempts to enter an atomic statement when it already owns the lock, it succeeds immediately and the counter is incremented.
+Each time the process leaves an atomic statement, the counter is decremented.
 When the counter reaches 0, the lock is released.
 
-Execution of a `$yield` does not change the multiplicity; the process releases the lock but maintains the multiplicity,
+Execution of a `$yield` does not change the multiplicity counter; the process releases the lock but maintains the multiplicity,
 so that when the lock is re-obtained, the original multiplicity is still in place.