[PATCH v2] ARM:kexec:offline panic_smp_self_stop CPU

From: wangyufen <wangyufen@huawei.com>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: <linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <akpm@linux-foundation.org>,
	<kstewart@linuxfoundation.org>, <rppt@linux.vnet.ibm.com>,
	<gregkh@linuxfoundation.org>, <tglx@linutronix.de>,
	<pombredanne@nexb.com>, <weiyongjun1@huawei.com>,
	<huawei.libin@huawei.com>, Wangyufen <wangyufen@huawei.com>
Subject: [PATCH v2] ARM:kexec:offline panic_smp_self_stop CPU
Date: Fri, 2 Nov 2018 10:31:27 +0800	[thread overview]
Message-ID: <5BDBB6FF.6080907@huawei.com> (raw)
In-Reply-To: <20181101113430.GO30658@n2100.armlinux.org.uk>

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@huawei.com>
---
 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 9000d8b..d7b86e4 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -682,6 +682,21 @@ 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
  */
-- 
2.7.4


