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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Alexander Gordeev <agordeev@linux.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 33/64] s390/cpuinfo: fix wrong output when CPU0 is offline
Date:   Wed, 22 Apr 2020 11:57:17 +0200
Message-Id: <20200422095018.866565980@linuxfoundation.org>
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From: Alexander Gordeev <agordeev@linux.ibm.com>

[ Upstream commit 872f27103874a73783aeff2aac2b41a489f67d7c ]

/proc/cpuinfo should not print information about CPU 0 when it is offline.

Fixes: 281eaa8cb67c ("s390/cpuinfo: simplify locking and skip offline cpus early")
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
[heiko.carstens@de.ibm.com: shortened commit message]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/s390/kernel/processor.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kernel/processor.c b/arch/s390/kernel/processor.c
index 6fe2e1875058b..675d4be0c2b77 100644
--- a/arch/s390/kernel/processor.c
+++ b/arch/s390/kernel/processor.c
@@ -157,8 +157,9 @@ static void show_cpu_mhz(struct seq_file *m, unsigned long n)
 static int show_cpuinfo(struct seq_file *m, void *v)
 {
 	unsigned long n = (unsigned long) v - 1;
+	unsigned long first = cpumask_first(cpu_online_mask);
 
-	if (!n)
+	if (n == first)
 		show_cpu_summary(m, v);
 	if (!machine_has_cpu_mhz)
 		return 0;
@@ -171,6 +172,8 @@ static inline void *c_update(loff_t *pos)
 {
 	if (*pos)
 		*pos = cpumask_next(*pos - 1, cpu_online_mask);
+	else
+		*pos = cpumask_first(cpu_online_mask);
 	return *pos < nr_cpu_ids ? (void *)*pos + 1 : NULL;
 }
 
-- 
2.20.1