linux-kernel - [PATCH tip/core/rcu 1/4] locktorture: Print ratio of acquisitions, not failures

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Message-Id: <20200215000337.14667-1-paulmck@kernel.org>
Date:   Fri, 14 Feb 2020 16:03:34 -0800
From:   paulmck@...nel.org
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>
Subject: [PATCH tip/core/rcu 1/4] locktorture: Print ratio of acquisitions, not failures

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

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

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 99475a6..687c1d8 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -696,10 +696,10 @@ static void __torture_print_stats(char *page,
 		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",
-- 
2.9.5