[PATCH 1/7] rcutorture: Fix jitter.sh spin time

[Paul E. McKenney]

An embarrassing syntax error in jitter.sh makes for fixed spin time.
This commit therefore makes it be variable, as intended, albeit with
very coarse-grained adjustment.

Signed-off-by: Paul E. McKenney <paul...@kernel.org>
---
 .../selftests/rcutorture/bin/jitter.sh        | 27 ++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh 
b/tools/testing/selftests/rcutorture/bin/jitter.sh
index fd1ffaa5a1358e..3c1e5d3f88058c 100755
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -39,6 +39,22 @@ do
        fi
 done
 
+# Uses global variables startsecs, startns, endsecs, endns, and limit.
+# Exit code is success for time not yet elapsed and failure otherwise.
+function timecheck {
+       local done=`awk -v limit=$limit \
+                       -v startsecs=$startsecs \
+                       -v startns=$startns \
+                       -v endsecs=$endsecs \
+                       -v endns=$endns < /dev/null '
+               BEGIN {
+                       delta = (endsecs - startsecs) * 1000 * 1000;
+                       delta += int((endns - startns) / 1000);
+                       print delta >= limit;
+               }'`
+       return $done
+}
+
 while :
 do
        # Check for done.
@@ -85,15 +101,20 @@ do
        n=$(($n+1))
        sleep .$sleeptime
 
-       # Spin a random duration
+       # Spin a random duration, but with rather coarse granularity.
        limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
                srand(n + me + systime());
                printf("%06d", int(rand() * spinmax));
        }' < /dev/null`
        n=$(($n+1))
-       for i in {1..$limit}
+       startsecs=`date +%s`
+       startns=`date +%N`
+       endsecs=$startns
+       endns=$endns
+       while timecheck
        do
-               echo > /dev/null
+               endsecs=`date +%s`
+               endns=`date +%N`
        done
 done
 
-- 
2.40.1