linux-kernel - [PATCH 4.9 007/137] ARM: 8808/1: kexec:offline panic_smp_self

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Message-Id: <20190211141812.642736657@linuxfoundation.org>
Date:   Mon, 11 Feb 2019 15:18:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yufen Wang <wangyufen@...wei.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 007/137] ARM: 8808/1: kexec:offline panic_smp_self_stop CPU

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 82c08c3e7f171aa7f579b231d0abbc1d62e91974 ]

In case panic() and panic() called at the same time on different CPUS.
For example:
CPU 0:
  panic()
     __crash_kexec
       machine_crash_shutdown
         crash_smp_send_stop
       machine_kexec
         BUG_ON(num_online_cpus() > 1);

CPU 1:
  panic()
    local_irq_disable
    panic_smp_self_stop

If CPU 1 calls panic_smp_self_stop() before crash_smp_send_stop(), kdump
fails. CPU1 can't receive the ipi irq, CPU1 will be always online.
To fix this problem, this patch split out the panic_smp_self_stop()
and add set_cpu_online(smp_processor_id(), false).

Signed-off-by: Yufen Wang <wangyufen@...wei.com>
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm/kernel/smp.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index d2ce37da87d8..4b129aac7233 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -690,6 +690,21 @@ void smp_send_stop(void)
 		pr_warn("SMP: failed to stop secondary CPUs\n");
 }
 
+/* In case panic() and panic() called at the same time on CPU1 and CPU2,
+ * and CPU 1 calls panic_smp_self_stop() before crash_smp_send_stop()
+ * CPU1 can't receive the ipi irqs from CPU2, CPU1 will be always online,
+ * kdump fails. So split out the panic_smp_self_stop() and add
+ * set_cpu_online(smp_processor_id(), false).
+ */
+void panic_smp_self_stop(void)
+{
+	pr_debug("CPU %u will stop doing anything useful since another CPU has paniced\n",
+	         smp_processor_id());
+	set_cpu_online(smp_processor_id(), false);
+	while (1)
+		cpu_relax();
+}
+
 /*
  * not supported here
  */
-- 
2.19.1