linux-kernel - [PATCH 4.9 120/125] locktorture: Print ratio of acquisitions, not failures

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Message-Id: <20200422095051.906433563@linuxfoundation.org>
Date:   Wed, 22 Apr 2020 11:57:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Will Deacon <will@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Josh Triplett <josh@...htriplett.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 4.9 120/125] locktorture: Print ratio of acquisitions, not failures

From: Paul E. McKenney <paulmck@...nel.org>

commit 80c503e0e68fbe271680ab48f0fe29bc034b01b7 upstream.

The __torture_print_stats() function in locktorture.c carefully
initializes local variable "min" to statp[0].n_lock_acquired, but
then compares it to statp[i].n_lock_fail.  Given that the .n_lock_fail
field should normally be zero, and given the initialization, it seems
reasonable to display the maximum and minimum number acquisitions
instead of miscomputing the maximum and minimum number of failures.
This commit therefore switches from failures to acquisitions.

And this turns out to be not only a day-zero bug, but entirely my
own fault.  I hate it when that happens!

Fixes: 0af3fe1efa53 ("locktorture: Add a lock-torture kernel module")
Reported-by: Will Deacon <will@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Acked-by: Will Deacon <will@...nel.org>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Josh Triplett <josh@...htriplett.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/locking/locktorture.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -649,10 +649,10 @@ static void __torture_print_stats(char *
 		if (statp[i].n_lock_fail)
 			fail = true;
 		sum += statp[i].n_lock_acquired;
-		if (max < statp[i].n_lock_fail)
-			max = statp[i].n_lock_fail;
-		if (min > statp[i].n_lock_fail)
-			min = statp[i].n_lock_fail;
+		if (max < statp[i].n_lock_acquired)
+			max = statp[i].n_lock_acquired;
+		if (min > statp[i].n_lock_acquired)
+			min = statp[i].n_lock_acquired;
 	}
 	page += sprintf(page,
 			"%s:  Total: %lld  Max/Min: %ld/%ld %s  Fail: %d %s\n",