multithreading - Reader/Writer Locks in C++

 

You Only Need To Note This: only 1 single thread can acquire an upgrade_lock at one time.

 

 

others are very straightforward.

96  vote

1800 INFORMATION is more or less correct, but there are a few issues I wanted to correct. boost::shared_mutex _access;void reader(){ boost::shared_lock< boost::shared_mutex > lock(_access); // do work here, without anyone having exclusive access } void conditional_writer(){ boost::upgrade_lock< boost::shared_mutex > lock(_access); // do work here, without anyone having exclusive access if (something) { boost::upgrade_to_unique_lock< boost::shared_mutex > uniqueLock(lock); // do work here, but now you have exclusive access } // do more work here, without anyone having exclusive access } void unconditional_writer(){ boost::unique_lock< boost::shared_mutex > lock(_access); // do work here, with exclusive access }   Also Note, unlike a shared_lock, only a single thread can acquire an upgrade_lock at one time, even when it isn't upgraded (which I thought was awkward when I ran into it). So, if all your readers are conditional writers, you need to find another solution.