Re: [Boost-bugs] [Boost C++ Libraries] #7720: exception lock_error while intensive locking/unlocking of mutex

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #7720: exception lock_error while intensive locking/unlocking of mutex
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-09-17 08:00:41

#7720: exception lock_error while intensive locking/unlocking of mutex
--------------------------------+------------------------
  Reporter:  sergey.stepanov@…  |      Owner:  viboes
      Type:  Bugs               |     Status:  reopened
 Milestone:  Boost 1.54.0       |  Component:  thread
   Version:  Boost 1.51.0       |   Severity:  Regression
Resolution:                     |   Keywords:  lock_error
--------------------------------+------------------------
Changes (by duchungjava@…):

 * status:  closed => reopened
 * resolution:  fixed =>

Comment:

 To whom it may concern,

 On Boost 1.57, I can replicate this problem with the following code:
 {{{#!C++
 boost::shared_mutex mutex;

 void shared_proc() {
   while ( 1 ) {
     boost::shared_lock<boost::shared_mutex> lock(mutex);
     boost::this_thread::sleep_for(boost::chrono::seconds(2));
   }
 }
 void upgrade_proc() {
   while ( 1 ) {
     boost::upgrade_lock<boost::shared_mutex> lock(mutex);
     boost::this_thread::sleep_for(boost::chrono::milliseconds(1));
   }
 }
 int main() {
   boost::thread ts(boost::bind(shared_proc));
   boost::thread t1(boost::bind(upgrade_proc));
   boost::thread t2(boost::bind(upgrade_proc));

   ts.join();
   t1.join();
   t2.join();

   return 0;
 }
 }}}

 By testing this code with different Boost versions, I've confirmed that:
 1. Boost 1.56 doesn't throw exception
 2. Boost 1.57 and 1.59 throw exception instantly

 I think the root reason is: The variable state.shared_count in
 shared_mutex.hpp couldn't be decreased/reset properly when a shared_mutex
 is being used for both shared_lock and upgrade_lock.

 (I'm using Visual Studio 2012 in this test case)

 Yours sincerely,
 Hung Mai

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7720#comment:26>
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