From: nobu@...
Date: 2014-07-19T14:01:55+00:00
Subject: [ruby-core:63874] [ruby-trunk - Bug #10076] 2nd thread can't get mutex even though 1st thread released it (race)

Issue #10076 has been updated by Nobuyoshi Nakada.

Description updated

Thread fairness issue?
Checking interrupts seems to help it, but not sure.

~~~diff
diff --git a/thread.c b/thread.c
index 682e05f..6f67df6 100644
--- a/thread.c
+++ b/thread.c
@@ -4528,11 +4528,15 @@ rb_mutex_synchronize(VALUE mutex, VALUE (*func)(VALUE arg), VALUE arg)
 static VALUE
 rb_mutex_synchronize_m(VALUE self, VALUE args)
 {
+    VALUE ret;
+
     if (!rb_block_given_p()) {
 	rb_raise(rb_eThreadError, "must be called with a block");
     }
 
-    return rb_mutex_synchronize(self, rb_yield, Qundef);
+    ret = rb_mutex_synchronize(self, rb_yield, Qundef);
+    RUBY_VM_CHECK_INTS(GET_THREAD());
+    return ret;
 }
 
 void rb_mutex_allow_trap(VALUE self, int val)
~~~

----------------------------------------
Bug #10076: 2nd thread can't get mutex even though 1st thread released it (race)
https://bugs.ruby-lang.org/issues/10076#change-47898

* Author: Dmitry Maksyoma
* Status: Open
* Priority: Normal
* Assignee: 
* Category: lib
* Target version: 
* ruby -v: ruby 2.1.2p95 (2014-05-08 revision 45877) [i686-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
----------------------------------------
~~~ruby
require 'thread'

m = Mutex.new

Thread.abort_on_exception = true
Thread.new {
  loop {
    m.synchronize {
      puts 'got mutex in thread'
      sleep 0.1
    }
  }
}

loop {
  m.synchronize {
    puts 'got mutex in loop'
    sleep 1
  }
  # Without sleep, the thread above has no chance of getting the mutex.
  #sleep 0.1
}
~~~


---Files--------------------------------
monitor-test (344 Bytes)


-- 
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