linux-kernel - About Full c3-stop status.

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Date:   Fri, 10 Sep 2021 10:20:25 +0900
From:   Yun Levi <ppbuk5246@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>, preeti@...ux.vnet.ibm.com,
        mingo@...e.hu, rmk+lkml@....linux.org.uk,
        dmitri.vorobiev@...ial.com
Cc:     youngjun.park@...lab.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: About Full c3-stop status.

Hi all.

Sorry to interrupt you but I have a question while I am reading the
tick-broadcast codes.

When a cpu goes to c3-stop, I confirm it calls the
tick_broadcast_enter function with TICK_BROADCAST_ENTER.

While entering, it calls the broadcast_needs_cpu with current cpu.

In the last condition of broadcast_needs_cpu, it checks whether the
broadcast device is bound on this cpu.

However, except the ce_broadcast_hrtimer in tick-broadcast-hrtimer.c,
all other real devices set bound_on fields as 0, Therefore, it seems
that cpu 0 couldn't enter c3-stop though it has the feature.

My question is
     1. Couldn't cpu 0 enter c3-stop?
     2. If true, why don't we set bound_on fields specifically?

Thanks.

HTH.
Levi.