dma-buf/sw-sync: always taint the kernel when sw-sync is used

The SW-sync functionality should only be used for testing and debugging
since it is inherently unsave.

Signed-off-by: Christian König <[e-mail]>
Acked-by: Sumit Semwal <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/dma-buf/sw_sync.c

···
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/uaccess.h>
+#include <linux/panic.h>
 #include <linux/slab.h>
 #include <linux/sync_file.h>
 
···
 	struct sync_pt *pt;
 	struct sync_file *sync_file;
 	struct sw_sync_create_fence_data data;
+
+	/* SW sync fence are inherently unsafe and can deadlock the kernel */
+	add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 
 	if (fd < 0)
 		return fd;