mysql_selector.c: introduce the myslq lock

This fixes a race condition in para_server:

	parent			child

	real_query
				real_query
	mysql_store_result

This could cause para_server to hang in case the child process issued
a query which does not yield a result. It's hard to hit though. Fix is
to take the lock before the call to real_query, and release it after
mysql_store_result().

The patch also fixes a format string bug which was introduced by the patch
that switched to my_ulonglong for suitable variables in mysql_selector.c.
These need "%lli".

diff --git a/mysql_selector.c b/mysql_selector.c
index 8148fabe04310739a577b99add1783de94f0f14d..dedc96cc8ec6961bf118c78586bb3c5be037fb04 100644 (file)
--- a/mysql_selector.c
+++ b/mysql_selector.c
@@ -22,11 +22,13 @@
 #include "string.h"
 #include "user_list.h"
 #include "mysql_selector_command_list.h"
+#include "ipc.h"
 
 /** pointer to the shared memory area */
 extern struct misc_meta_data *mmd;
 
 static void *mysql_ptr = NULL;
+static int mysql_lock;
 
 /**
  * contains name/replacement pairs used by s_a_r_list()
@@ -152,7 +154,7 @@ __must_check __malloc static char *s_a_r_list(const struct para_macro *macro_lis
        return ret;
 }
 
-static int real_query(const char *query)
+static int lockless_real_query(const char *query)
 {
        if (!mysql_ptr)
                return -E_NOTCONN;
@@ -165,19 +167,32 @@ static int real_query(const char *query)
        return 1;
 }
 
+static int real_query(const char *query)
+{
+       int ret;
+
+       mutex_lock(mysql_lock);
+       ret = lockless_real_query(query);
+       mutex_unlock(mysql_lock);
+       return ret;
+}
+
 /*
  * Use open connection given by mysql_ptr to query server. Returns a
  * result pointer on succes and NULL on errors
  */
 static struct MYSQL_RES *get_result(const char *query)
 {
-       void *result;
+       void *result = NULL;
 
-       if (real_query(query) < 0)
-               return NULL;
+       mutex_lock(mysql_lock);
+       if (lockless_real_query(query) < 0)
+               goto out;
        result = mysql_store_result(mysql_ptr);
        if (!result)
                PARA_ERROR_LOG("%s", "store_result error\n");
+out:
+       mutex_unlock(mysql_lock);
        return result;
 }
 /*
@@ -1947,7 +1962,7 @@ static int com_vrfy_clean(int fd, int argc, __a_unused char *argv[])
                goto out;
        }
        if (vrfy_mode) {
-               send_va_buffer(fd, "found %i invalid entr%s\n", num_rows,
+               send_va_buffer(fd, "found %lli invalid entr%s\n", num_rows,
                        num_rows == 1? "y" : "ies");
                ret = print_results(fd, result, top, left, num_rows - 1, right);
                goto out;
@@ -2244,11 +2259,18 @@ out:
 
 static void shutdown_connection(void)
 {
+       int ret;
+
        if (mysql_ptr) {
                PARA_NOTICE_LOG("%s", "shutting down mysql connection\n");
                mysql_close(mysql_ptr);
                mysql_ptr = NULL;
        }
+       if (mysql_lock) {
+               ret = mutex_destroy(mysql_lock);
+               if (ret < 0)
+                       PARA_ERROR_LOG("%s\n", PARA_STRERROR(-ret));
+       }
 }
 
 /**
@@ -2280,6 +2302,10 @@ int mysql_selector_init(struct audio_file_selector *db)
        db->get_audio_file_list = server_get_audio_file_list;
        db->update_audio_file = update_audio_file_server_handler;
        db->shutdown = shutdown_connection;
+       ret = mutex_new();
+       if (ret < 0)
+               return ret;
+       mysql_lock = ret;
        ret = init_mysql_server();
        if (ret < 0)
                PARA_WARNING_LOG("%s\n", PARA_STRERROR(-ret));