Re: [Libevent-users] std::threads

[Azat Khuzhin <a3at.mail@xxxxxxxxx>]

On Sun, Mar 20, 2016 at 11:10:47AM -0400, Michael wrote:
> >Ugh, you don't need this wrapper, since evbuffer_get_length() will use
> >bufferevent's lock automatically.
> 
> bufferevent_lock(bev_) and bufferevent_unlock(bev_) should not be used????
> 
> How about bufferevent_write()???

evbuffer/bufferevent's are thread-safe, so the answer is *no*.

If we take a look at bufferevent_write() code we will see:
  evbuffer_add()

Which is:
  int
  evbuffer_add(struct evbuffer *buf, const void *data_in, size_t datlen)
  {
      ...
      EVBUFFER_LOCK(buf);

And this is:
#define EVBUFFER_LOCK(buffer) EVLOCK_LOCK((buffer)->lock, 0)
#define EVLOCK_LOCK(lockvar,mode) if (lockvar) evthreadimpl_lock_lock_(mode, lockvar);

So IOW if buf->lock != NULL then it is thread-safe, and as I already mentioned
it will be not null if you pass BEV_OPT_THREADSAFE to bufferevent (and also you
need to enable one of locking mechanisms pthread/win32/your-own), since in this
case bufferevent->{output,input} will have the save lock as bufferevent.

I hope this will help.

Regards,
Azat.
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