diff options
Diffstat (limited to 'html/075channel.mu.html')
| -rw-r--r-- | html/075channel.mu.html | 68 |
1 files changed, 46 insertions, 22 deletions
diff --git a/html/075channel.mu.html b/html/075channel.mu.html index 6f34b054..4912015e 100644 --- a/html/075channel.mu.html +++ b/html/075channel.mu.html @@ -21,6 +21,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color .Comment { color: #9090ff; } .Constant { color: #00a0a0; } .Special { color: #c00000; } +.CommentedCode { color: #6c6c6c; } .muControl { color: #c0a020; } --> </style> @@ -33,20 +34,17 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color </head> <body> <pre id='vimCodeElement'> -<span class="Comment"># Mu synchronizes using channels rather than locks, like Erlang and Go.</span> -<span class="Comment">#</span> -<span class="Comment"># The two ends of a channel will usually belong to different routines, but</span> -<span class="Comment"># each end should (currently) only be used by a single one. Don't try to read</span> -<span class="Comment"># from or write to it from multiple routines at once.</span> +<span class="Comment"># Mu synchronizes between routines using channels rather than locks, like</span> +<span class="Comment"># Erlang and Go.</span> <span class="Comment">#</span> <span class="Comment"># Key properties of channels:</span> <span class="Comment">#</span> -<span class="Comment"># a) Writing to a full channel or reading from an empty one will put the</span> -<span class="Comment"># current routine in 'waiting' state until the operation can be completed.</span> +<span class="Comment"># a) Writing to a full channel or reading from an empty one will put the</span> +<span class="Comment"># current routine in 'waiting' state until the operation can be completed.</span> <span class="Comment">#</span> -<span class="Comment"># b) Writing to a channel implicitly performs a deep copy, to prevent</span> -<span class="Comment"># addresses from being shared between routines, thereby causing race</span> -<span class="Comment"># conditions.</span> +<span class="Comment"># b) Writing to a channel implicitly performs a deep copy. This prevents</span> +<span class="Comment"># addresses from being shared between routines, and therefore eliminates all</span> +<span class="Comment"># possibility of race conditions.</span> <span class="muScenario">scenario</span> channel [ run [ @@ -62,9 +60,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color ] <span class="muData">container</span> channel:_elem [ - <span class="Comment"># To avoid locking, writer and reader will never write to the same location.</span> - <span class="Comment"># So channels will include fields in pairs, one for the writer and one for the</span> - <span class="Comment"># reader.</span> + lock:boolean <span class="Comment"># inefficient but simple: serialize all reads as well as writes</span> first-full:number <span class="Comment"># for write</span> first-free:number <span class="Comment"># for read</span> <span class="Comment"># A circular buffer contains values from index first-full up to (but not</span> @@ -105,13 +101,25 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color assert out, <span class="Constant">[write to null channel]</span> chan:address:channel:_elem<span class="Special"> <- </span>get *out, <span class="Constant">chan:offset</span> <span class="Constant"> <channel-write-initial></span> + <span class="Comment"># block until lock is acquired AND queue has room</span> + lock:location<span class="Special"> <- </span>get-location *chan, <span class="Constant">lock:offset</span> +<span class="CommentedCode">#? $print [write], 10/newline</span> <span class="Delimiter">{</span> - <span class="Comment"># block if chan is full</span> - full:boolean<span class="Special"> <- </span>channel-full? chan - <span class="muControl">break-unless</span> full - full-address:location<span class="Special"> <- </span>get-location *chan, <span class="Constant">first-full:offset</span> - wait-for-location full-address +<span class="CommentedCode">#? $print [trying to acquire lock for writing], 10/newline</span> + wait-for-reset-then-set lock +<span class="CommentedCode">#? $print [lock acquired for writing], 10/newline</span> + full?:boolean<span class="Special"> <- </span>channel-full? chan + <span class="muControl">break-unless</span> full? +<span class="CommentedCode">#? $print [but channel is full; relinquishing lock], 10/newline</span> + <span class="Comment"># channel is full; relinquish lock and give a reader the opportunity to</span> + <span class="Comment"># create room on it</span> + reset lock + current-routine-is-blocked + switch <span class="Comment"># avoid spinlocking</span> + <span class="muControl">loop</span> <span class="Delimiter">}</span> + current-routine-is-unblocked +<span class="CommentedCode">#? $print [performing write], 10/newline</span> <span class="Comment"># store a deep copy of val</span> circular-buffer:address:array:_elem<span class="Special"> <- </span>get *chan, <span class="Constant">data:offset</span> free:number<span class="Special"> <- </span>get *chan, <span class="Constant">first-free:offset</span> @@ -128,6 +136,8 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color <span class="Delimiter">}</span> <span class="Comment"># write back</span> *chan<span class="Special"> <- </span>put *chan, <span class="Constant">first-free:offset</span>, free +<span class="CommentedCode">#? $print [relinquishing lock after writing], 10/newline</span> + reset lock ] <span class="muRecipe">def</span> read in:address:source:_elem<span class="muRecipe"> -> </span>result:_elem, eof?:boolean, in:address:source:_elem [ @@ -136,14 +146,25 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color assert in, <span class="Constant">[read on null channel]</span> eof?<span class="Special"> <- </span>copy <span class="Constant">0/false</span> <span class="Comment"># default result</span> chan:address:channel:_elem<span class="Special"> <- </span>get *in, <span class="Constant">chan:offset</span> + <span class="Comment"># block until lock is acquired AND queue has data</span> + lock:location<span class="Special"> <- </span>get-location *chan, <span class="Constant">lock:offset</span> +<span class="CommentedCode">#? $print [read], 10/newline</span> <span class="Delimiter">{</span> - <span class="Comment"># block if chan is empty</span> +<span class="CommentedCode">#? $print [trying to acquire lock for reading], 10/newline</span> + wait-for-reset-then-set lock +<span class="CommentedCode">#? $print [lock acquired for reading], 10/newline</span> empty?:boolean<span class="Special"> <- </span>channel-empty? chan <span class="muControl">break-unless</span> empty? +<span class="CommentedCode">#? $print [but channel is empty; relinquishing lock], 10/newline</span> + <span class="Comment"># channel is empty; relinquish lock and give a writer the opportunity to</span> + <span class="Comment"># add to it</span> + reset lock + current-routine-is-blocked <span class="Constant"> <channel-read-empty></span> - free-address:location<span class="Special"> <- </span>get-location *chan, <span class="Constant">first-free:offset</span> - wait-for-location free-address + switch <span class="Comment"># avoid spinlocking</span> + <span class="muControl">loop</span> <span class="Delimiter">}</span> + current-routine-is-unblocked <span class="Comment"># pull result off</span> full:number<span class="Special"> <- </span>get *chan, <span class="Constant">first-full:offset</span> circular-buffer:address:array:_elem<span class="Special"> <- </span>get *chan, <span class="Constant">data:offset</span> @@ -162,6 +183,8 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color <span class="Delimiter">}</span> <span class="Comment"># write back</span> *chan<span class="Special"> <- </span>put *chan, <span class="Constant">first-full:offset</span>, full +<span class="CommentedCode">#? $print [relinquishing lock after reading], 10/newline</span> + reset lock ] <span class="muRecipe">def</span> clear in:address:source:_elem<span class="muRecipe"> -> </span>in:address:source:_elem [ @@ -344,6 +367,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color <span class="Delimiter">{</span> <span class="muControl">break-unless</span> closed? empty-result:address:_elem<span class="Special"> <- </span>new <span class="Constant">_elem:type</span> + current-routine-is-unblocked <span class="muControl">return</span> *empty-result, <span class="Constant">1/true</span> <span class="Delimiter">}</span> ] @@ -424,7 +448,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color <span class="Delimiter">}</span> <span class="Comment"># copy line into 'buffered-out'</span> i:number<span class="Special"> <- </span>copy <span class="Constant">0</span> - line-contents:address:array:character<span class="Special"> <- </span>get *line, <span class="Constant">data:offset</span> + line-contents:text<span class="Special"> <- </span>get *line, <span class="Constant">data:offset</span> max:number<span class="Special"> <- </span>get *line, <span class="Constant">length:offset</span> <span class="Delimiter">{</span> done?:boolean<span class="Special"> <- </span>greater-or-equal i, max |