[or-cvs] [tor/master 3/5] Better fix for 2190: defer libevent->controller messages instead of dropping
nickm at torproject.org
nickm at torproject.org
Tue Dec 21 20:46:25 UTC 2010
Author: Nick Mathewson <nickm at torproject.org>
Date: Fri, 19 Nov 2010 22:52:32 -0500
Subject: Better fix for 2190: defer libevent->controller messages instead of dropping
Commit: d166d18643197c57ba98d3a476df26c605554b26
---
changes/bug2190 | 5 +++
src/common/log.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++---
src/common/torlog.h | 5 ++-
src/or/main.c | 3 ++
4 files changed, 79 insertions(+), 7 deletions(-)
diff --git a/changes/bug2190 b/changes/bug2190
index 92ecba7..0591acb 100644
--- a/changes/bug2190
+++ b/changes/bug2190
@@ -4,3 +4,8 @@
running Libevent with debug logging enabled, and running Tor
with a controller watching for low-severity log messages.
Bugfix on 0.1.0.2-rc. Fixes bug 2190.
+ - Make Libevent log messages get delievered to controllers later,
+ and not from inside the Libevent log handler. This prevents
+ unsafe reentrant Libevent calls while still letting the log
+ messages get through.
+
diff --git a/src/common/log.c b/src/common/log.c
index 0ccda53..f26c5ef 100644
--- a/src/common/log.c
+++ b/src/common/log.c
@@ -103,6 +103,17 @@ static logfile_t *logfiles = NULL;
static int syslog_count = 0;
#endif
+/** Represents a log message that we are going to send to callback-driven
+ * loggers once we can do so in a non-reentrant way. */
+typedef struct pending_cb_message_t {
+ int severity;
+ log_domain_mask_t domain;
+ char *msg;
+} pending_cb_message_t;
+
+/** Log messages waiting to be replayed onto callback-based logs */
+static smartlist_t *pending_cb_messages = NULL;
+
#define LOCK_LOGS() STMT_BEGIN \
tor_mutex_acquire(&log_mutex); \
STMT_END
@@ -268,6 +279,10 @@ logv(int severity, log_domain_mask_t domain, const char *funcname,
* interesting and hard to diagnose effects */
assert(severity >= LOG_ERR && severity <= LOG_DEBUG);
LOCK_LOGS();
+
+ if (smartlist_len(pending_cb_messages))
+ flush_pending_log_callbacks();
+
lf = logfiles;
while (lf) {
if (! (lf->severities->masks[SEVERITY_MASK_IDX(severity)] & domain)) {
@@ -278,10 +293,6 @@ logv(int severity, log_domain_mask_t domain, const char *funcname,
lf = lf->next;
continue;
}
- if (lf->callback && (domain & LD_NOCB)) {
- lf = lf->next;
- continue;
- }
if (lf->seems_dead) {
lf = lf->next;
continue;
@@ -316,7 +327,15 @@ logv(int severity, log_domain_mask_t domain, const char *funcname,
lf = lf->next;
continue;
} else if (lf->callback) {
- lf->callback(severity, domain, end_of_prefix);
+ if (domain & LD_NOCB) {
+ pending_cb_message_t *msg = tor_malloc(sizeof(pending_cb_message_t));
+ msg->severity = severity;
+ msg->domain = domain;
+ msg->msg = tor_strdup(end_of_prefix);
+ smartlist_add(pending_cb_messages, msg);
+ } else {
+ lf->callback(severity, domain, end_of_prefix);
+ }
lf = lf->next;
continue;
}
@@ -555,6 +574,8 @@ init_logging(void)
tor_mutex_init(&log_mutex);
log_mutex_initialized = 1;
}
+ if (pending_cb_messages == NULL)
+ pending_cb_messages = smartlist_create();
}
/** Add a log handler to receive messages during startup (before the real
@@ -613,6 +634,48 @@ change_callback_log_severity(int loglevelMin, int loglevelMax,
UNLOCK_LOGS();
}
+/** If there are any log messages that were genered with LD_NOCB waiting to
+ * be sent to callback-based loggers, send them now. */
+void
+flush_pending_log_callbacks(void)
+{
+ logfile_t *lf;
+ smartlist_t *messages, *messages_tmp;
+
+ LOCK_LOGS();
+ if (0 == smartlist_len(pending_cb_messages)) {
+ UNLOCK_LOGS();
+ return;
+ }
+
+ messages = pending_cb_messages;
+ pending_cb_messages = smartlist_create();
+ do {
+ SMARTLIST_FOREACH_BEGIN(messages, pending_cb_message_t *, msg) {
+ const int severity = msg->severity;
+ const int domain = msg->domain;
+ for (lf = logfiles; lf; lf = lf->next) {
+ if (! lf->callback || lf->seems_dead ||
+ ! (lf->severities->masks[SEVERITY_MASK_IDX(severity)] & domain)) {
+ continue;
+ }
+ lf->callback(severity, domain, msg->msg);
+ }
+ tor_free(msg->msg);
+ tor_free(msg);
+ } SMARTLIST_FOREACH_END(msg);
+ smartlist_clear(messages);
+
+ messages_tmp = pending_cb_messages;
+ pending_cb_messages = messages;
+ messages = messages_tmp;
+ } while (smartlist_len(messages));
+
+ smartlist_free(messages);
+
+ UNLOCK_LOGS();
+}
+
/** Close any log handlers added by add_temp_log() or marked by
* mark_logs_temp(). */
void
diff --git a/src/common/torlog.h b/src/common/torlog.h
index 8b6cd1b..73c6906 100644
--- a/src/common/torlog.h
+++ b/src/common/torlog.h
@@ -95,8 +95,8 @@
/** Number of logging domains in the code. */
#define N_LOGGING_DOMAINS 20
-/** This log message is not safe to send to a callback-based logger.
- * Used as a flag, not a log domain. */
+/** This log message is not safe to send to a callback-based logger
+ * immediately. Used as a flag, not a log domain. */
#define LD_NOCB (1u<<31)
typedef uint32_t log_domain_mask_t;
@@ -141,6 +141,7 @@ void rollback_log_changes(void);
void mark_logs_temp(void);
void change_callback_log_severity(int loglevelMin, int loglevelMax,
log_callback cb);
+void flush_pending_log_callbacks(void);
void log_set_application_name(const char *name);
/* Outputs a message to stdout */
diff --git a/src/or/main.c b/src/or/main.c
index 9bdbbc1..e13215b 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -893,6 +893,9 @@ run_scheduled_events(time_t now)
signewnym_impl(now);
}
+ /* 0c. If we've deferred log messages for the controller, handle them now */
+ flush_pending_log_callbacks();
+
/** 1a. Every MIN_ONION_KEY_LIFETIME seconds, rotate the onion keys,
* shut down and restart all cpuworkers, and update the directory if
* necessary.
--
1.7.1
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