dma-mapping fix for 5.11

- fix a kernel crash in the new dma-mapping benchmark test (Barry Song)
 -----BEGIN PGP SIGNATURE-----
 
 iQI/BAABCgApFiEEgdbnc3r/njty3Iq9D55TZVIEUYMFAmAZGkkLHGhjaEBsc3Qu
 ZGUACgkQD55TZVIEUYNF0A//WjFHsPCMbbhlOlCMcRD/I1+JLQYchjlWp48wAzxq
 K3fmGnLlsvd3lCyUQzLLcUMSs+NsaTlzNNtH+MSNfGvX3x/8Mz9F57AgJ7C2xlaD
 XXbob5SKAqls6UFw6sBhlNbUe/l3Tup7LgqyCqQGRfpftycO7Vk70oHfFir0xqeB
 IX2s2s9UK+iePRtqfhyOylipIPXG3A3TnDJ+T3x5wsw6m4ejr8TVUVNsA1Xg0mha
 xsMVELyPwp3pEYp0+LNZsvtRC6uv7MeNf11mqmtk9VOZtrnS1VsD+ZPeNXzoCP3n
 5iipcFGeiz8ac2bdldIjwYa4wyIBZR1kOOQ+1+gq42/Hs/Eu9N3aQydhgrzw8ZnY
 MxUHbHazhpB2qt2lxyMjODVRKFdEt2FrkP7a7d3guw2Il4o2f14g9MZS72c5H5jk
 Vg90VSW8UQr51MKamZkgLeIgFaqVTOkgXO5h7e+dfD/XMgm4Vt3qsjcBSQfTcCrj
 4efmJwUvyv8x13HXoSvistKXG6kTH+rBtbxD6RvzE2C9dasb5L3mYIj+loQJqU7+
 u/+X9ZUVHTvXlH7j7Fc9vBgCUf0VlZJ8N3LXl5zN7zRP40vcvudlhyNj1PWhiUlu
 G5RBhuyTm3jd+NqCYE7XCqf+dvA7BGgkW2LZM/qAhlZgmJaWLwlJwAe0XA0KR9uR
 U5w=
 =l+IX
 -----END PGP SIGNATURE-----

Merge tag 'dma-mapping-5.11-1' of git://git.infradead.org/users/hch/dma-mapping

Pull dma-mapping fix from Christoph Hellwig:
 "Fix a kernel crash in the new dma-mapping benchmark test (Barry Song)"

* tag 'dma-mapping-5.11-1' of git://git.infradead.org/users/hch/dma-mapping:
  dma-mapping: benchmark: fix kernel crash when dma_map_single fails

kernel/dma/map_benchmark.c

@@ -147,8 +147,10 @@ static int do_map_benchmark(struct map_benchmark_data *map)
 	atomic64_set(&map->sum_sq_unmap, 0);
 	atomic64_set(&map->loops, 0);
 
-	for (i = 0; i < threads; i++)
+	for (i = 0; i < threads; i++) {
+		get_task_struct(tsk[i]);
 		wake_up_process(tsk[i]);
+	}
 
 	msleep_interruptible(map->bparam.seconds * 1000);
 
@@ -183,6 +185,8 @@ static int do_map_benchmark(struct map_benchmark_data *map)
 	}
 
 out:
+	for (i = 0; i < threads; i++)
+		put_task_struct(tsk[i]);
 	put_device(map->dev);
 	kfree(tsk);
 	return ret;