cblas: clarify XERBLA handler lifetime

Author: moluopro

cblas.h

@@ -59,10 +59,12 @@ typedef void (*openblas_dojob_callback)(int thread_num, void *jobdata, int dojob
 typedef void (*openblas_threads_callback)(int sync, openblas_dojob_callback dojob, int numjobs, size_t jobdata_elsize, void *jobdata, int dojob_data);
 void openblas_set_threads_callback_function(openblas_threads_callback callback);
 
-/* Set the process-wide error handler called by XERBLA. The callback's routine
- * name is valid for name_length bytes and is not necessarily NUL-terminated.
- * Installation is thread-safe, returns the previous handler, and accepts NULL
- * to restore OpenBLAS' default handler. */
+/* Replace the XERBLA handler for this OpenBLAS instance and return the
+ * previous handler. Passing NULL restores the default. Callbacks may run
+ * concurrently and must be thread-safe. The name and info pointers are valid
+ * only during the callback; name spans name_length bytes and need not be
+ * NUL-terminated. Replacement is thread-safe but does not wait for in-flight
+ * calls, so the previous handler must remain loaded until they complete. */
 #ifndef OPENBLAS_XERBLA_HANDLER_DEFINED
 #define OPENBLAS_XERBLA_HANDLER_DEFINED
 typedef void (*openblas_xerbla_handler)(const char *name,