kunit: remove timeout dependence on sysctl_hung_task_timeout_seconds

In discussion of how to handle timeouts, it was noted that if
sysctl_hung_task_timeout_seconds is exceeded for a kunit test,
the test task will be killed and an oops generated.  This should
suffice as a means of debugging such timeout issues for now.

Hence remove use of sysctl_hung_task_timeout_secs, which has the
added benefit of avoiding the need to export that symbol from
the core kernel.
Co-developed-by: Knut Omang <knut.omang@oracle.com>
Signed-off-by: Knut Omang <knut.omang@oracle.com>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/kunit/try-catch.c

@@ -11,7 +11,6 @@
 #include <linux/completion.h>
 #include <linux/kernel.h>
 #include <linux/kthread.h>
-#include <linux/sched/sysctl.h>
 
 #include "try-catch-impl.h"
 
@@ -33,8 +32,6 @@ static int kunit_generic_run_threadfn_adapter(void *data)
 
 static unsigned long kunit_test_timeout(void)
 {
-	unsigned long timeout_msecs;
-
 	/*
 	 * TODO(brendanhiggins@google.com): We should probably have some type of
 	 * variable timeout here. The only question is what that timeout value
@@ -51,22 +48,11 @@ static unsigned long kunit_test_timeout(void)
 	 *
 	 * For more background on this topic, see:
 	 * https://mike-bland.com/2011/11/01/small-medium-large.html
-	 */
-	if (sysctl_hung_task_timeout_secs) {
-		/*
-		 * If sysctl_hung_task is active, just set the timeout to some
-		 * value less than that.
 	 *
-		 * In regards to the above TODO, if we decide on variable
-		 * timeouts, this logic will likely need to change.
+	 * If tests timeout due to exceeding sysctl_hung_task_timeout_secs,
+	 * the task will be killed and an oops generated.
 	 */
-		timeout_msecs = (sysctl_hung_task_timeout_secs - 1) *
-				MSEC_PER_SEC;
-	} else {
-		timeout_msecs = 300 * MSEC_PER_SEC; /* 5 min */
-	}
-
-	return timeout_msecs;
+	return 300 * MSEC_PER_SEC; /* 5 min */
 }
 
 void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)