commit 7be50c26e8b2ec0bd0121d5e8b2dc55de977cf5a Author: Nick Mathewson nickm@torproject.org Date: Mon Nov 14 18:12:29 2011 -0500

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. --- changes/bug4457_master | 6 ++++++ src/common/compat_libevent.c | 37 ++++++++++++++++++++++++++++++++++++- 2 files changed, 42 insertions(+), 1 deletions(-)

diff --git a/changes/bug4457_master b/changes/bug4457_master new file mode 100644 index 0000000..d394643 --- /dev/null +++ b/changes/bug4457_master @@ -0,0 +1,6 @@ + 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. diff --git a/src/common/compat_libevent.c b/src/common/compat_libevent.c index c533461..7a28c9b 100644 --- a/src/common/compat_libevent.c +++ b/src/common/compat_libevent.c @@ -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();