Fix race accessing settings.verbosity

As reported by ThreadSanitizer:

WARNING: ThreadSanitizer: data race (pid=34992)
  Read of size 4 at 0x7f98b38b5bf4 by main thread:
    #0 run_event_loop /home/daver/repos/couchbase/server/memcached/daemon/connections.cc:170 (memcached+0x0000000c7049)
    #1 event_handler /home/daver/repos/couchbase/server/memcached/daemon/memcached.cc:6912 (memcached+0x0000000d7b34)
    #2 event_persist_closure /home/couchbase/jenkins/workspace/cbdeps-build/label/ubuntu14.04/release/sherlock/deps/packages/build/libevent/libevent-prefix/src/libevent/event.c:1319 (libevent_core-2.0.so.5+0x00000000b6c7)
    #3 __libc_start_main /build/buildd/eglibc-2.19/csu/libc-start.c:287 (libc.so.6+0x000000021ec4)

  Previous write of size 4 at 0x7f98b38b5bf4 by thread T19 (mutexes: write M45860):
    #0 verbosity_executor(conn*, void*) /home/daver/repos/couchbase/server/memcached/daemon/memcached.cc:3600 (memcached+0x0000000df219)
    #1 process_bin_packet(conn*) /home/daver/repos/couchbase/server/memcached/daemon/memcached.cc:5053 (memcached+0x0000000d2100)
    #2 run_event_loop /home/daver/repos/couchbase/server/memcached/daemon/connections.cc:174 (memcached+0x0000000c70c3)
    #3 event_handler /home/daver/repos/couchbase/server/memcached/daemon/memcached.cc:6912 (memcached+0x0000000d7b34)
    #4 event_persist_closure /home/couchbase/jenkins/workspace/cbdeps-build/label/ubuntu14.04/release/sherlock/deps/packages/build/libevent/libevent-prefix/src/libevent/event.c:1319 (libevent_core-2.0.so.5+0x00000000b6c7)
    #5 platform_thread_wrap /home/daver/repos/couchbase/server/platform/src/cb_pthreads.c:23 (libplatform.so.0.1.0+0x000000003730)

Change-Id: I2ae83312a532c67b2e3915e0c604e4e60558a8a7
Reviewed-on: http://review.couchbase.org/52487
Tested-by: buildbot <[email protected]>
Reviewed-by: Trond Norbye <[email protected]>

daemon/breakpad.cc

@@ -25,16 +25,13 @@
 #  else
 #    error Unsupported platform for breakpad, cannot compile.
 #  endif
+#include "settings.h"
 
 #include "memcached/extension_loggers.h"
 #include <platform/backtrace.h>
 
 #include <stdlib.h>
 
-extern "C" {
-    extern struct settings settings;
-}
-
 using namespace google_breakpad;
 
 ExceptionHandler* handler;

daemon/config_parse.cc

@@ -92,6 +92,11 @@ static bool get_absolute_file(const char *file, const char **value,
 }
 
 
+/** Given a JSON element {i} with the name {key}, attempt to convert
+ *  it's value to an integer and store the result in {value}. Returns
+ *  true on success; else returns false and sets {error_msg} to point
+ *  to message describing the any error.
+ */
 static bool get_int_value(cJSON *i, const char *key, int* value,
                           char **error_msg) {
     switch (i->type) {
@@ -370,7 +375,9 @@ static bool get_max_packet_size(cJSON *o, struct settings *settings,
 
 static bool get_verbosity(cJSON *o, struct settings *settings,
                           char **error_msg) {
-    if (get_int_value(o, o->string, &settings->verbose, error_msg)) {
+    int verbosity;
+    if (get_int_value(o, o->string, &verbosity, error_msg)) {
+        settings->verbose.store(verbosity);
         settings->has.verbose = true;
         return true;
     } else {
@@ -1331,11 +1338,11 @@ static void dyna_reconfig_verbosity(const struct settings *new_settings) {
     if (new_settings->has.verbose &&
         new_settings->verbose != settings.verbose) {
         int old_verbose = settings.verbose;
-        settings.verbose = new_settings->verbose;
+        settings.verbose.store(new_settings->verbose);
         perform_callbacks(ON_LOG_LEVEL, NULL, NULL);
         settings.extensions.logger->log(EXTENSION_LOG_NOTICE, NULL,
             "Changed verbosity from %d to %d", old_verbose,
-            settings.verbose);
+            settings.verbose.load());
     }
 }
 

daemon/memcached.cc

@@ -5657,7 +5657,7 @@ static void process_stat_settings(ADD_STAT add_stats, void *c) {
         }
     }
 
-    APPEND_STAT("verbosity", "%d", settings.verbose);
+    APPEND_STAT("verbosity", "%d", settings.verbose.load());
     APPEND_STAT("num_threads", "%d", settings.num_threads);
     APPEND_STAT("reqs_per_event_high_priority", "%d",
                 settings.reqs_per_event_high_priority);
@@ -7713,7 +7713,7 @@ static EXTENSION_LOGGER_DESCRIPTOR* get_logger(void)
 static EXTENSION_LOG_LEVEL get_log_level(void)
 {
     EXTENSION_LOG_LEVEL ret;
-    switch (settings.verbose) {
+    switch (settings.verbose.load()) {
     case 0: ret = EXTENSION_LOG_NOTICE; break;
     case 1: ret = EXTENSION_LOG_INFO; break;
     case 2: ret = EXTENSION_LOG_DEBUG; break;

daemon/settings.h

@@ -19,9 +19,7 @@
 
 #include <memcached/engine.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+#include <atomic>
 
 /**
  * An enumeration with constants for the various protocols supported
@@ -94,7 +92,7 @@ struct settings {
     const char *rbac_file; /* The file containing RBAC information */
     bool rbac_privilege_debug; /* see manpage */
     bool require_sasl;      /* require SASL auth */
-    int verbose;            /* level of versosity to log at. */
+    std::atomic<int> verbose;            /* level of versosity to log at. */
     int bio_drain_buffer_sz; /* size of the SSL bio buffers */
     bool datatype;          /* is datatype support enabled? */
     const char *root; /* The root directory of the installation */
@@ -169,7 +167,3 @@ struct settings {
 };
 
 extern struct settings settings;
-
-#ifdef __cplusplus
-} // extern "C"
-#endif