[tip: core/rcu] torture: Use "jittering" file to control jitter.sh execution

[tip: core/rcu] torture: Use "jittering" file to control jitter.sh execution

[tip-bot2 for Paul E. McKenney]

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     37812c9429722824859788cf754dd3e33f546908
Gitweb:        https://git.kernel.org/tip/37812c9429722824859788cf754dd3e33f546908
Author:        Paul E. McKenney <paulmck@kernel.org>
AuthorDate:    Thu, 11 Feb 2021 10:39:28 -08:00
Committer:     Paul E. McKenney <paulmck@kernel.org>
CommitterDate: Mon, 08 Mar 2021 14:23:01 -08:00

torture: Use "jittering" file to control jitter.sh execution

Currently, jitter.sh execution is controlled by a time limit and by the
"kill" command.  The former allowed jitter.sh to run uselessly past
the end of a set of runs that panicked during boot, and the latter is
vulnerable to PID reuse.  This commit therefore introduces a "jittering"
file in the date-stamp directory within "res" that must be present for
the jitter.sh scripts to continue executing.  The time limit is still
in place in order to avoid disturbing runs featuring large trace dumps,
but the removal of the "jittering" file handles the panic-during-boot
scenario without relying on PIDs.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/jitter.sh | 10 ++++++----
 tools/testing/selftests/rcutorture/bin/kvm.sh    |  5 ++++-
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 188b864..ed0ea86 100755
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -5,10 +5,11 @@
 # of this script is to inflict random OS jitter on a concurrently running
 # test.
 #
-# Usage: jitter.sh me duration [ sleepmax [ spinmax ] ]
+# Usage: jitter.sh me duration jittering-path [ sleepmax [ spinmax ] ]
 #
 # me: Random-number-generator seed salt.
 # duration: Time to run in seconds.
+# jittering-path: Path to file whose removal will stop this script.
 # sleepmax: Maximum microseconds to sleep, defaults to one second.
 # spinmax: Maximum microseconds to spin, defaults to one millisecond.
 #
@@ -18,8 +19,9 @@
 
 me=$(($1 * 1000))
 duration=$2
-sleepmax=${3-1000000}
-spinmax=${4-1000}
+jittering=$3
+sleepmax=${4-1000000}
+spinmax=${5-1000}
 
 n=1
 
@@ -47,7 +49,7 @@ do
 	fi
 
 	# Check for stop request.
-	if test -f "$TORTURE_STOPFILE"
+	if ! test -f "$jittering"
 	then
 		exit 1;
 	fi
diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 1f5f872..48da4cd 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -503,14 +503,17 @@ function dump(first, pastlast, batchnum)
 	print "then"
 	print "\techo ---- Starting kernels. `date` | tee -a " rd "log";
 	print "\techo > " rd "jitter_pids"
+	print "\ttouch " rd "jittering"
 	for (j = 0; j < njitter; j++) {
-		print "\tjitter.sh " j " " dur " " ja[2] " " ja[3] "&"
+		print "\tjitter.sh " j " " dur " " rd "jittering " ja[2] " " ja[3] "&"
 		print "\techo $! >> " rd "jitter_pids"
 	}
 	print "\twhile ls $runfiles > /dev/null 2>&1"
 	print "\tdo"
 	print "\t\t:"
 	print "\tdone"
+	print "\trm -f " rd "jittering"
+	print "\twait"
 	print "\techo ---- All kernel runs complete. `date` | tee -a " rd "log";
 	print "else"
 	print "\twait"