linux-kernel - [tip: core/rcu] refperf: Work around 64-bit division

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Date:   Fri, 31 Jul 2020 09:22:55 -0000
From:   "tip-bot2 for Arnd Bergmann" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     kbuild test robot <lkp@...el.com>, valdis.kletnieks@...edu,
        Randy Dunlap <rdunlap@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: core/rcu] refperf: Work around 64-bit division

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

Commit-ID:     7c944d7c67daee84e3c756bb74ad2f32b28c41cf
Gitweb:        https://git.kernel.org/tip/7c944d7c67daee84e3c756bb74ad2f32b28c41cf
Author:        Arnd Bergmann <arnd@...db.de>
AuthorDate:    Fri, 29 May 2020 14:36:26 -07:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Mon, 29 Jun 2020 12:00:45 -07:00

refperf: Work around 64-bit division

A 64-bit division was introduced in refperf, breaking compilation
on all 32-bit architectures:

kernel/rcu/refperf.o: in function `main_func':
refperf.c:(.text+0x57c): undefined reference to `__aeabi_uldivmod'

Fix this by using div_u64 to mark the expensive operation.

[ paulmck: Update primitive and format per Nathan Chancellor. ]
Fixes: bd5b16d6c88d ("refperf: Allow decimal nanoseconds")
Reported-by: kbuild test robot <lkp@...el.com>
Reported-by: Valdis Klētnieks <valdis.kletnieks@...edu>
Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/refperf.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c
index 063eeb0..80d4490 100644
--- a/kernel/rcu/refperf.c
+++ b/kernel/rcu/refperf.c
@@ -478,7 +478,7 @@ static int main_func(void *arg)
 		if (torture_must_stop())
 			goto end;
 
-		result_avg[exp] = 1000 * process_durations(nreaders) / (nreaders * loops);
+		result_avg[exp] = div_u64(1000 * process_durations(nreaders), nreaders * loops);
 	}
 
 	// Print the average of all experiments
@@ -489,9 +489,13 @@ static int main_func(void *arg)
 	strcat(buf, "Runs\tTime(ns)\n");
 
 	for (exp = 0; exp < nruns; exp++) {
+		u64 avg;
+		u32 rem;
+
 		if (errexit)
 			break;
-		sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, result_avg[exp] / 1000, (int)(result_avg[exp] % 1000));
+		avg = div_u64_rem(result_avg[exp], 1000, &rem);
+		sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem);
 		strcat(buf, buf1);
 	}