Commit 7be50c26 authored by Nick Mathewson's avatar Nick Mathewson 🦀
Browse files

Disable IOCP and retry event_base_new_with_config once on failure 

This is a fancier bug4457 workaround for 0.2.3.  In 0.2.2, we could
just tell Libevent "Don't enable locking!" so it wouldn't try to make
the event_base notifiable.  But for IOCP, we need a notifiable base.
(Eventually, we'll want a notifiable base for other stuff, like
multithreaded crypto.)  So the solution is to try a full-featured
initialization, and then retry with all the options turned off if that
fails.
parent cf811713

changes/bug4457_master

0 → 100644
+6 −0
Original line number Diff line number Diff line 
  o Minor features:

    - When we fail to initialize Libevent, retry with IOCP disabled so we

      don't need to turn on multi-threading support in Libevent, which in

      turn requires a working socketpair().  This is a workaround for bug

      4457, which affects Libevent versions from 2.0.1-alpha through

      2.0.15-stable.

src/common/compat_libevent.c

+36 −1
Original line number Diff line number Diff line
@@ -195,7 +195,14 @@ tor_libevent_initialize(tor_libevent_cfg *torcfg) 


#ifdef HAVE_EVENT2_EVENT_H

  {

    struct event_config *cfg = event_config_new();

    int attempts = 0;

    int using_threads;

    struct event_config *cfg;



  retry:

    ++attempts;

    using_threads = 0;

    cfg = event_config_new();

    tor_assert(cfg);



#if defined(MS_WINDOWS) && defined(USE_BUFFEREVENTS)
@@ -203,9 +210,18 @@ tor_libevent_initialize(tor_libevent_cfg *torcfg) 
      evthread_use_windows_threads();

      event_config_set_flag(cfg, EVENT_BASE_FLAG_STARTUP_IOCP);

      using_iocp_bufferevents = 1;

      using_threads = 1;

    } else {

      using_iocp_bufferevents = 0;

    }

#endif



    if (!using_threads) {

      /* Telling Libevent not to try to turn locking on can avoid a needless

       * socketpair() attempt. */

      event_config_set_flag(cfg, EVENT_BASE_FLAG_NOLOCK);

    }



#if defined(LIBEVENT_VERSION_NUMBER) && LIBEVENT_VERSION_NUMBER >= V(2,0,7)

    if (torcfg->num_cpus > 0)

      event_config_set_num_cpus_hint(cfg, torcfg->num_cpus);
@@ -220,6 +236,25 @@ tor_libevent_initialize(tor_libevent_cfg *torcfg) 
    the_event_base = event_base_new_with_config(cfg);



    event_config_free(cfg);



    if (using_threads && the_event_base == NULL && attempts < 2) {

      /* This could be a socketpair() failure, which can happen sometimes on

       * windows boxes with obnoxious firewall rules.  Downgrade and try

       * again. */

#if defined(MS_WINDOWS) && defined(USE_BUFFEREVENTS)

      if (torcfg->disable_iocp == 0) {

        log_warn(LD_GENERAL, "Unable to initialize Libevent. Trying again with "

                 "IOCP disabled.");

      } else

#endif

      {

          log_warn(LD_GENERAL, "Unable to initialize Libevent. Trying again.");

      }



      torcfg->disable_iocp = 1;

      goto retry;

    }



  }

#else

  the_event_base = event_init();