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From:   Zhouyi Zhou <zhouzhouyi@gmail.com>
To:     mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu,
        atrajeev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, lance@osuosl.org, paulmck@kernel.org,
        rcu@vger.kernel.org
Cc:     Zhouyi Zhou <zhouzhouyi@gmail.com>
Subject: [PATCH linux-next][RFC] powerpc: fix HOTPLUG error in rcutorture
Date:   Mon, 10 Oct 2022 10:33:15 +0800
Message-Id: <20221010023315.98396-1-zhouzhouyi@gmail.com>
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I think we should avoid torture offline the cpu who do tick timer
when nohz full is running.

Tested on PPC VM of Open Source Lab of Oregon State University.
The test results show that after the fix, the success rate of
rcutorture is improved.
After:
Successes: 40 Failures: 9
Before:
Successes: 38 Failures: 11

I examined the console.log and Make.out files one by one, no new
compile error or test error is introduced by above fix.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
---
Dear PPC developers

I found this bug when trying to do rcutorture tests in ppc VM of
Open Source Lab of Oregon State University:

ubuntu@ubuntu:~/linux-next/tools/testing/selftests/rcutorture/res/2022.09.30-01.06.22-torture$ find . -name "console.log.diags"|xargs grep HOTPLUG
./results-scftorture/NOPREEMPT/console.log.diags:WARNING: HOTPLUG FAILURES NOPREEMPT
./results-rcutorture/TASKS03/console.log.diags:WARNING: HOTPLUG FAILURES TASKS03
./results-rcutorture/TREE04/console.log.diags:WARNING: HOTPLUG FAILURES TREE04
./results-scftorture-kasan/NOPREEMPT/console.log.diags:WARNING: HOTPLUG FAILURES NOPREEMPT
./results-rcutorture-kasan/TASKS03/console.log.diags:WARNING: HOTPLUG FAILURES TASKS03
./results-rcutorture-kasan/TREE04/console.log.diags:WARNING: HOTPLUG FAILURES TREE04

I tried to fix this bug.

Thanks for your patience and guidance ;-)

Thanks 
Zhouyi
--
 arch/powerpc/kernel/sysfs.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index ef9a61718940..be9c0e45337e 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -4,6 +4,7 @@
 #include <linux/smp.h>
 #include <linux/percpu.h>
 #include <linux/init.h>
+#include <linux/tick.h>
 #include <linux/sched.h>
 #include <linux/export.h>
 #include <linux/nodemask.h>
@@ -21,6 +22,7 @@
 #include <asm/firmware.h>
 #include <asm/idle.h>
 #include <asm/svm.h>
+#include "../../../kernel/time/tick-internal.h"
 
 #include "cacheinfo.h"
 #include "setup.h"
@@ -1151,7 +1153,11 @@ static int __init topology_init(void)
 		 * CPU.  For instance, the boot cpu might never be valid
 		 * for hotplugging.
 		 */
-		if (smp_ops && smp_ops->cpu_offline_self)
+		if (smp_ops && smp_ops->cpu_offline_self
+#ifdef CONFIG_NO_HZ_FULL
+		    && !(tick_nohz_full_running && tick_do_timer_cpu == cpu)
+#endif
+		    )
 			c->hotpluggable = 1;
 #endif
 
-- 
2.25.1