coredump: add cond_resched() to dump_user_range

The loop between elf_core_dump() and dump_user_range() can run for
so long that the system shows softlockup messages, with side effects
like workqueues and RCU getting stuck on the core dumping CPU.

Add a cond_resched() in dump_user_range() to avoid that softlockup.

Signed-off-by: Rik van Riel <riel@surriel.com>
Link: https://lore.kernel.org/r/20241010113651.50cb0366@imladris.surriel.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/coredump.c

@@ -951,6 +951,7 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
 		} else {
 			dump_skip(cprm, PAGE_SIZE);
 		}
+		cond_resched();
 	}
 	dump_page_free(dump_page);
 	return 1;