* [PATCH] thread_timeout: document additional caveats
@ 2012-07-19 20:14 Eric Wong
[not found] ` <20120719201403.GA11657-yBiyF41qdooeIZ0/mPfg9Q@public.gmane.org>
0 siblings, 1 reply; 2+ messages in thread
From: Eric Wong @ 2012-07-19 20:14 UTC (permalink / raw)
To: rainbows-talk-GrnCvJ7WPxnNLxjTenLetw
Again, for the one thousandth time, timing out threads is very
tricky business :<
---
Pushed to "master" of git://bogomips.org/rainbows and updated
http://rainbows.rubyforge.org/Rainbows/ThreadTimeout.html
lib/rainbows/thread_timeout.rb | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/lib/rainbows/thread_timeout.rb b/lib/rainbows/thread_timeout.rb
index 4f62aba..8348272 100644
--- a/lib/rainbows/thread_timeout.rb
+++ b/lib/rainbows/thread_timeout.rb
@@ -44,6 +44,15 @@
# does not expose a monotonic clock for users, so don't change
# the system time while this is running. All servers should be
# running ntpd anyways.
+#
+# "ensure" clauses may not fire properly or be interrupted during
+# execution, so do not mix this module with code which relies on "ensure".
+# (This is also true for the "Timeout" module in the Ruby standard library)
+#
+# "recursive locking" ThreadError exceptions may occur if
+# ThreadTimeout fires while a Mutex is locked (because "ensure"
+# clauses may not fire properly).
+
class Rainbows::ThreadTimeout
# :stopdoc:
--
Eric Wong
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^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] thread_timeout: document additional caveats
[not found] ` <20120719201403.GA11657-yBiyF41qdooeIZ0/mPfg9Q@public.gmane.org>
@ 2012-07-20 2:40 ` Eric Wong
0 siblings, 0 replies; 2+ messages in thread
From: Eric Wong @ 2012-07-20 2:40 UTC (permalink / raw)
To: rainbows-talk-GrnCvJ7WPxnNLxjTenLetw
Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org> wrote:
> Again, for the one thousandth time, timing out threads is very
> tricky business :<
On a related note, it looks like Thread.control_interrupt
landed in Ruby trunk (http://svn.ruby-lang.org/repos/ruby/trunk r36470)
Perhaps the future for interrupting long-running threads is
less bleak.
+/*
+ * call-seq:
+ * Thread.control_interrupt(hash) { ... } -> result of the block
+ *
+ * Thread.control_interrupt controls interrupt timing.
+ *
+ * _interrupt_ means asynchronous event and corresponding procedure
+ * by Thread#raise, Thread#kill, signal trap (not supported yet)
+ * and main thread termination (if main thread terminates, then all
+ * other thread will be killed).
+ *
+ * _hash_ has pairs of ExceptionClass and TimingSymbol. TimingSymbol
+ * is one of them:
+ * - :immediate Invoke interrupt immediately.
+ * - :on_blocking Invoke interrupt while _BlockingOperation_.
+ * - :never Never invoke interrupt.
+ *
+ * _BlockingOperation_ means that the operation will block the calling thread,
+ * such as read and write. On CRuby implementation, _BlockingOperation_ is
+ * operation executed without GVL.
+ *
+ * Masked interrupts are delayed until they are enabled.
+ * This method is similar to sigprocmask(3).
+ *
+ * TODO (DOC): control_interrupt is stacked.
+ * TODO (DOC): check ancestors.
+ * TODO (DOC): to prevent all interrupt, {Object => :never} works.
+ *
+ * NOTE: Asynchronous interrupts are difficult to use.
+ * If you need to communicate between threads,
+ * please consider to use another way such as Queue.
+ * Or use them with deep understanding about this method.
+ *
+ *
+ * # example: Guard from Thread#raise
+ * th = Thread.new do
+ * Thead.control_interrupt(RuntimeError => :never) {
+ * begin
+ * # Thread#raise doesn't interrupt here.
+ * # You can write resource allocation code safely.
+ * Thread.control_interrupt(RuntimeError => :immediate) {
+ * # ...
+ * # It is possible to be interrupted by Thread#raise.
+ * }
+ * ensure
+ * # Thread#raise doesn't interrupt here.
+ * # You can write resource dealocation code safely.
+ * end
+ * }
+ * end
+ * Thread.pass
+ * # ...
+ * th.raise "stop"
+ *
+ * # example: Guard from TimeoutError
+ * require 'timeout'
+ * Thread.control_interrupt(TimeoutError => :never) {
+ * timeout(10){
+ * # TimeoutError doesn't occur here
+ * Thread.control_interrupt(TimeoutError => :on_blocking) {
+ * # possible to be killed by TimeoutError
+ * # while blocking operation
+ * }
+ * # TimeoutError doesn't occur here
+ * }
+ * }
+ *
+ * # example: Stack control settings
+ * Thread.control_interrupt(FooError => :never) {
+ * Thread.control_interrupt(BarError => :never) {
+ * # FooError and BarError are prohibited.
+ * }
+ * }
+ *
+ * # example: check ancestors
+ * Thread.control_interrupt(Exception => :never) {
+ * # all exceptions inherited from Exception are prohibited.
+ * }
+ *
+ */
+
+/*
+ * call-seq:
+ * Thread.check_interrupt() -> nil
+ *
+ * Check queued interrupts.
+ *
+ * If there are queued interrupts, process respective procedures.
+ *
+ * This method can be defined as the following Ruby code:
+ *
+ * def Thread.check_interrupt
+ * Thread.control_interrupt(Object => :immediate) {
+ * Thread.pass
+ * }
+ * end
+ *
+ * Examples:
+ *
+ * th = Thread.new{
+ * Thread.control_interrupt(RuntimeError => :on_blocking){
+ * while true
+ * ...
+ * # reach safe point to invoke interrupt
+ * Thread.check_interrupt
+ * ...
+ * end
+ * }
+ * }
+ * ...
+ * th.raise # stop thread
+ *
+ * NOTE: This example can be described by the another code.
+ * You need to keep to avoid asynchronous interrupts.
+ *
+ * flag = true
+ * th = Thread.new{
+ * Thread.control_interrupt(RuntimeError => :on_blocking){
+ * while true
+ * ...
+ * # reach safe point to invoke interrupt
+ * break if flag == false
+ * ...
+ * end
+ * }
+ * }
+ * ...
+ * flag = false # stop thread
+ */
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2012-07-19 20:14 [PATCH] thread_timeout: document additional caveats Eric Wong
[not found] ` <20120719201403.GA11657-yBiyF41qdooeIZ0/mPfg9Q@public.gmane.org>
2012-07-20 2:40 ` Eric Wong
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