spin_rw_mutex upgrade/downgrade not compiling

[Nav]

I took an example from the TBB tutorial pdf.

[bash]std::vector MyVector;
typedef spin_rw_mutex MyVectorMutexType;
MyVectorMutexType MyVectorMutex;
void AddKeyIfMissing( const string& key ) {
    // Obtain a reader lock on MyVectorMutex
    MyVectorMutexType::scoped_lock
lock(MyVectorMutex,/*is_writer=*/false);
    size_t n = MyVector.size();
    for( size_t i=0; i        if( MyVector==key ) return;
    if( !MyVectorMutex.upgrade_to_writer() )
        // Check if key was added while lock was temporarily released
        for( int i=n; i           if(MyVector==key ) return;
    vector.push_back(key);
}
[/bash]

And created my own program.

[bash]#include
#include
#include 

using namespace std;
using namespace tbb;

typedef spin_rw_mutex myMutex;
myMutex sm;
int i=0;

void writerFunction() 
{ 
   {
      myMutex::scoped_lock lock(sm,/*is writer=*/true);
      ++i;
      sm.downgrade_to_reader();
      //sm.upgrade_to_writer();
      cout<<"wrote value "<<   }
}


int main()
{
   tbb_thread my_thread1(writerFunction);
   tbb_thread my_thread2(writerFunction);
       
   my_thread1.join();
   my_thread2.join();
    
   cout<<"Value of i = "  << i <}[/bash]

It shows the following compilation error:

[bash]spin_rw_mutex.cpp: In function void writerFunction():
spin_rw_mutex.cpp:25: error: class myMutex has no member named downgrade_to_reader
bash: ./spin_rw_mutex: No such file or directory
[/bash]

I had a look at the spin_rw_mutex_v3.hpp file. It shows that downgrade_to_reader is within scoped_lock. If that's so, I'm confused as to how the function is accessed as a mutex instance member in the tutorial example. What am I doing/understanding wrong?

[Alexey-Kukanov · Accepted solution]

It's an error in the Tutorial; thank you for pointing it out!
Upgrading/downgrading should be done through the scoped_lock object, not through the mutex object. We will fix the Tutorial.

[Nav]

Ah! So I just had to use
lock.downgrade_to_reader();
T'was as simple as that! Thanks! :)