linux-kernel - [PATCH tip/core/rcu 11/30] refperf: Dynamically allocate thread-summary output buffer

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Message-Id: <20200623003013.26252-11-paulmck@kernel.org>
Date:   Mon, 22 Jun 2020 17:29:54 -0700
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>
Subject: [PATCH tip/core/rcu 11/30] refperf: Dynamically allocate thread-summary output buffer

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

Currently, the buffer used to accumulate the thread-summary output is
fixed size, which will cause problems if someone decides to run on a large
number of PCUs.  This commit therefore dynamically allocates this buffer.

[ paulmck: Fix memory allocation as suggested by KASAN. ]
Cc: Joel Fernandes (Google) <joel@...lfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/refperf.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c
index 75b9cce..fc940e3 100644
--- a/kernel/rcu/refperf.c
+++ b/kernel/rcu/refperf.c
@@ -301,9 +301,12 @@ u64 process_durations(int n)
 	int i;
 	struct reader_task *rt;
 	char buf1[64];
-	char buf[512];
+	char *buf;
 	u64 sum = 0;
 
+	buf = kmalloc(128 + nreaders * 32, GFP_KERNEL);
+	if (!buf)
+		return 0;
 	buf[0] = 0;
 	sprintf(buf, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)",
 		exp_idx);
@@ -322,6 +325,7 @@ u64 process_durations(int n)
 
 	PERFOUT("%s\n", buf);
 
+	kfree(buf);
 	return sum;
 }
 
-- 
2.9.5