On Mon, Mar 25, 2019 at 09:51:23PM +0800, lantianyu1986@gmail.com wrote:
From: Lan Tianyu Tianyu.Lan@microsoft.com
When add "nosmt" parameter, kernel still boots up all logical cpus once and set CR4.MCE on each CPU. This is to avoid shutting down machine when a broadacasted MCE is observed CR4.MCE=0b. (Detail please see comment in the cpu_smt_allowed()). Smt cpus will bring up and bring down during kernel boot with "nosmt" parameter.
When CONFIG_HOTPLUG_CPU=Y, CPU_DYING callbacks will be called inside stop-machine and irq is disabled. This happens in the take_cpu_down() callback. When CONFIG_HOTPLUG_CPU=N,CPU_DYING callbacks will be called with irq enabled.
smpcfd_dying_cpu() is one of CPU_DYING callbacks and it assumes to be called when irq is disabled. smpcfd_dying_cpu() calls flush_smp_call_ function_queue() which requires to be called with irq disabled.
When CONFIG_HOTPLUG_CPU=N and add "nosmt" parameter, smpcfd_dying_cpu() is called with irq enalbed and this triggers BUG_ON(!irqs_disabled()) in the irq_work_run_list(). This patch is to fix the issue.
Fixes: 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") Signed-off-by: Lan Tianyu Tianyu.Lan@microsoft.com
kernel/smp.c | 5 +++++ 1 file changed, 5 insertions(+)
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This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
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