linux-kernel - Re: Unexplained long boot delays [Was Re: [GIT PULL] RCU changes for v6.9]

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Date: Wed, 13 Mar 2024 18:15:18 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Florian Fainelli <f.fainelli@...il.com>
Cc: "Russell King (Oracle)" <linux@...linux.org.uk>, Joel Fernandes <joel@...lfernandes.org>, 
	Boqun Feng <boqun.feng@...il.com>, Anna-Maria Behnsen <anna-maria@...utronix.de>, 
	linux-kernel@...r.kernel.org, kernel-team@...a.com, paulmck@...nel.org, 
	mingo@...nel.org, tglx@...utronix.de, rcu@...r.kernel.org, 
	neeraj.upadhyay@....com, urezki@...il.com, qiang.zhang1211@...il.com, 
	frederic@...nel.org, bigeasy@...utronix.de, chenzhongjin@...wei.com, 
	yangjihong1@...wei.com, rostedt@...dmis.org, 
	Justin Chen <justin.chen@...adcom.com>
Subject: Re: Unexplained long boot delays [Was Re: [GIT PULL] RCU changes for v6.9]

On Wed, 13 Mar 2024 at 16:29, Florian Fainelli <f.fainelli@...il.com> wrote:
>
> On this specific commit 7ee988770326fca440472200c3eb58935fe712f6, there
> is a 100% failure for at least 3 devices out of the 16 that are running
> the test.

Hmm.  I have no idea what is going on, and the unimac-mdio probe
function (one of the things that seem to take forever on your setup)
looks fairly simple.

There doesn't even seem to be any timers involved.

That said - one of the things it does is

  unimac_mdio_probe ->
    unimac_mdio_clk_set ->
      clk_prepare_enable

and maybe that's a pattern, because you report that
brcm_pcie_resume_noirq is another problem spot (on resume).

And guess what brcm_pcie_resume_noirq() does?

Yup. clk_prepare_enable().

So I'm wondering if there's some interaction with some clock driver?
That might explain why it shows up on some arm platforms but not
elsewhere.

I may be barking *entirely* up the wrong tree, though. I was just
looking at that unimac probe and going "there's absolutely _nothing_
timer-related here" and that clk thing looked like it might at least
have _some_ relevance.

            Linus