commit b0224bf7282f2ec968a46e35a2a8dab1ddaf0667 Author: Nick Mathewson <nickm@torproject.org> Date: Tue May 1 10:05:22 2018 -0400 Add a mechanism for the logging system to report queued callbacks Sometimes the logging system will queue a log message for later. When it does this, the callback will either get flushed at the next safe time, or from the second-elapsed callback. But we're trying to eliminate the second-elapsed callback, so let's make a way for the log system to tell its users about this. --- src/common/log.c | 25 +++++++++++++++++++++++++ src/common/torlog.h | 2 ++ 2 files changed, 27 insertions(+) diff --git a/src/common/log.c b/src/common/log.c index 922e9dd38..ebd50f62d 100644 --- a/src/common/log.c +++ b/src/common/log.c @@ -170,6 +170,9 @@ typedef struct pending_log_message_t { /** Log messages waiting to be replayed onto callback-based logs */ static smartlist_t *pending_cb_messages = NULL; +/** Callback to invoke when pending_cb_messages becomes nonempty. */ +static pending_callback_callback pending_cb_cb = NULL; + /** Log messages waiting to be replayed once the logging system is initialized. */ static smartlist_t *pending_startup_messages = NULL; @@ -538,6 +541,9 @@ logfile_deliver(logfile_t *lf, const char *buf, size_t msg_len, smartlist_add(pending_cb_messages, pending_log_message_new(severity,domain,NULL,msg_after_prefix)); *callbacks_deferred = 1; + if (smartlist_len(pending_cb_messages) == 1 && pending_cb_cb) { + pending_cb_cb(); + } } } else { lf->callback(severity, domain, msg_after_prefix); @@ -825,6 +831,7 @@ logs_free_all(void) logfiles = NULL; messages = pending_cb_messages; pending_cb_messages = NULL; + pending_cb_cb = NULL; messages2 = pending_startup_messages; pending_startup_messages = NULL; UNLOCK_LOGS(); @@ -988,6 +995,24 @@ add_temp_log(int min_severity) } /** + * Register "cb" as the callback to call when there are new pending log + * callbacks to be flushed with flush_pending_log_callbacks(). + * + * Note that this callback, if present, can be invoked from any thread. + * + * This callback must not log. + * + * It is intentional that this function contains the name "callback" twice: it + * sets a "callback" to be called on the condition that there is a "pending + * callback". + **/ +void +logs_set_pending_callback_callback(pending_callback_callback cb) +{ + pending_cb_cb = cb; +} + +/** * Add a log handler to send messages in <b>severity</b> * to the function <b>cb</b>. */ diff --git a/src/common/torlog.h b/src/common/torlog.h index ac632ff52..de389883c 100644 --- a/src/common/torlog.h +++ b/src/common/torlog.h @@ -154,6 +154,8 @@ int add_android_log(const log_severity_list_t *severity, const char *android_identity_tag); #endif // HAVE_ANDROID_LOG_H. int add_callback_log(const log_severity_list_t *severity, log_callback cb); +typedef void (*pending_callback_callback)(void); +void logs_set_pending_callback_callback(pending_callback_callback cb); void logs_set_domain_logging(int enabled); int get_min_log_level(void); void switch_logs_debug(void);