LinuxPPC-Dev Archive on
 help / color / Atom feed
From: Michael Ellerman <>
To: Nathan Lynch <>,
Subject: Re: [PATCH] powerpc/pseries: correctly track irq state in default idle
Date: Thu, 19 Sep 2019 20:25:56 +1000 (AEST)
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, 2019-09-10 at 22:52:44 UTC, Nathan Lynch wrote:
> prep_irq_for_idle() is intended to be called before entering
> H_CEDE (and it is used by the pseries cpuidle driver). However the
> default pseries idle routine does not call it, leading to mismanaged
> lazy irq state when the cpuidle driver isn't in use. Manifestations of
> this include:
> * Dropped IPIs in the time immediately after a cpu comes
>   online (before it has installed the cpuidle handler), making the
>   online operation block indefinitely waiting for the new cpu to
>   respond.
> * Hitting this WARN_ON in arch_local_irq_restore():
> 	/*
> 	 * We should already be hard disabled here. We had bugs
> 	 * where that wasn't the case so let's dbl check it and
> 	 * warn if we are wrong. Only do that when IRQ tracing
> 	 * is enabled as mfmsr() can be costly.
> 	 */
> 	if (WARN_ON_ONCE(mfmsr() & MSR_EE))
> 		__hard_irq_disable();
> Call prep_irq_for_idle() from pseries_lpar_idle() and honor its
> result.
> Fixes: 363edbe2614a ("powerpc: Default arch idle could cede processor on pseries")
> Signed-off-by: Nathan Lynch <>

Applied to powerpc next, thanks.


      reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-10 22:52 Nathan Lynch
2019-09-19 10:25 ` Michael Ellerman [this message]

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LinuxPPC-Dev Archive on

Archives are clonable:
	git clone --mirror linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ \
	public-inbox-index linuxppc-dev

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone