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Disable IOCP and retry event_base_new_with_config once on failure

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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.
This commit is contained in:
Nick Mathewson
2011-11-14 18:12:29 -05:00
parent cf8117136c
commit 7be50c26e8
2 changed files with 42 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
changes/bug4457_master
+6
View File
@@ -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.
src/common/compat_libevent.c
+36 -1
View File
@@ -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();