[PATCH AUTOSEL 4.20 023/304] ARM: 8808/1: kexec:offline panic_smp_self_stop CPU

Sasha Levin
2019-01-28T17:51:13Z

From: Yufen Wang <wangyufen@huawei.com>

[ 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@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.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 12a6172263c0..3bf82232b1be 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -724,6 +724,21 @@ 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