MDEV-20183 data race at safe_mutex_lock()

kevgs · kevgs · commit 7db999322c00 · 2019-07-26T12:36:06.000+03:00
fix is simple: just move mp-&gt;file under mp-&gt;global protection
diff --git a/mysys/thr_mutex.c b/mysys/thr_mutex.c
@@ -237,6 +237,8 @@ int safe_mutex_lock(safe_mutex_t *mp, myf my_flags, const char *file,
   int error;
   DBUG_PRINT("mutex", ("%s (0x%lx) locking", mp->name ? mp->name : "Null",
                        (ulong) mp));
+
+  pthread_mutex_lock(&mp->global);
   if (!mp->file)
   {
     fprintf(stderr,
@@ -245,8 +247,6 @@ int safe_mutex_lock(safe_mutex_t *mp, myf my_flags, const char *file,
     fflush(stderr);
     abort();
   }
-
-  pthread_mutex_lock(&mp->global);
   if (mp->count > 0)
   {
     /*

Original file line number	Diff line number	Diff line change
`@@ -237,6 +237,8 @@ int safe_mutex_lock(safe_mutex_t mp, myf my_flags, const char file,`
`237`	`237`	`int error;`
`238`	`238`	`DBUG_PRINT("mutex", ("%s (0x%lx) locking", mp->name ? mp->name : "Null",`
`239`	`239`	`(ulong) mp));`
	`240`	`+`
	`241`	`+ pthread_mutex_lock(&mp->global);`
`240`	`242`	`if (!mp->file)`
`241`	`243`	`{`
`242`	`244`	`fprintf(stderr,`
`@@ -245,8 +247,6 @@ int safe_mutex_lock(safe_mutex_t mp, myf my_flags, const char file,`
`245`	`247`	`fflush(stderr);`
`246`	`248`	`abort();`
`247`	`249`	`}`
`248`		`-`
`249`		`- pthread_mutex_lock(&mp->global);`
`250`	`250`	`if (mp->count > 0)`
`251`	`251`	`{`
`252`	`252`	`/*`