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MDEV-34534 main.plugin_load(daemon_example) - AddressSanitizer: Joining already joined thread, aborting

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Joining with a thread that has previously been joined results in undefined behavior.

This example plugin performs the same join to the same thread a few
lines later. ASAN keeps track of this and fails.

Make the behaviour defined by joining only once.

Thanks Vladislav Vaintroub for looking up the behaviour.

While here;
* init/deinit function argument was actually used.
* correct code comments
* attribute define not needed

Thanks Marko Mäkelä for review and suggesting other
fixes.
This commit is contained in:
Daniel Black 2024-11-18 21:02:19 +11:00
parent b65504b8db
commit 1d6502b4f4
1 changed files with 7 additions and 17 deletions
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24
plugin/daemon_example/daemon_example.cc
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@ -26,14 +26,6 @@
#include "m_string.h" // strlen #include "m_string.h" // strlen
#include "sql_plugin.h" // st_plugin_int #include "sql_plugin.h" // st_plugin_int
/*
Disable __attribute__() on non-gcc compilers.
*/
#if !defined(__attribute__) && !defined(__GNUC__)
#define __attribute__(A)
#endif
#define HEART_STRING_BUFFER 100 #define HEART_STRING_BUFFER 100
struct mysql_heartbeat_context struct mysql_heartbeat_context
@ -77,14 +69,14 @@ pthread_handler_t mysql_heartbeat(void *p)
daemon_example_plugin_init() daemon_example_plugin_init()
DESCRIPTION DESCRIPTION
Starts up heartbeatbeat thread Starts up heartbeat thread (mysql_heartbeat)
RETURN VALUE RETURN VALUE
0 success 0 success
1 failure (cannot happen) 1 failure (cannot happen)
*/ */
static int daemon_example_plugin_init(void *p __attribute__ ((unused))) static int daemon_example_plugin_init(void *p)
{ {
DBUG_ENTER("daemon_example_plugin_init"); DBUG_ENTER("daemon_example_plugin_init");
@ -150,7 +142,7 @@ static int daemon_example_plugin_init(void *p __attribute__ ((unused)))
*/ */
static int daemon_example_plugin_deinit(void *p __attribute__ ((unused))) static int daemon_example_plugin_deinit(void *p)
{ {
DBUG_ENTER("daemon_example_plugin_deinit"); DBUG_ENTER("daemon_example_plugin_deinit");
char buffer[HEART_STRING_BUFFER]; char buffer[HEART_STRING_BUFFER];
@ -162,6 +154,10 @@ static int daemon_example_plugin_deinit(void *p __attribute__ ((unused)))
pthread_cancel(con->heartbeat_thread); pthread_cancel(con->heartbeat_thread);
pthread_join(con->heartbeat_thread, NULL); pthread_join(con->heartbeat_thread, NULL);
/*
As thread is joined, we can close the file it writes to and
free the memory it uses.
*/
localtime_r(&result, &tm_tmp); localtime_r(&result, &tm_tmp);
my_snprintf(buffer, sizeof(buffer), my_snprintf(buffer, sizeof(buffer),
@ -174,12 +170,6 @@ static int daemon_example_plugin_deinit(void *p __attribute__ ((unused)))
tm_tmp.tm_sec); tm_tmp.tm_sec);
my_write(con->heartbeat_file, (uchar*) buffer, strlen(buffer), MYF(0)); my_write(con->heartbeat_file, (uchar*) buffer, strlen(buffer), MYF(0));
/*
Need to wait for the hearbeat thread to terminate before closing
the file it writes to and freeing the memory it uses.
*/
pthread_join(con->heartbeat_thread, NULL);
my_close(con->heartbeat_file, MYF(0)); my_close(con->heartbeat_file, MYF(0));
my_free(con); my_free(con);