From: Peter Zijlstra <peterz@infradead.org>
To: James Morse <james.morse@arm.com>
Cc: Waiman Long <longman@redhat.com>,
Zhenzhong Duan <zhenzhong.duan@oracle.com>,
LKML <linux-kernel@vger.kernel.org>,
SRINIVAS <srinivas.eeda@oracle.com>
Subject: Re: Question about qspinlock nest
Date: Thu, 10 Jan 2019 21:12:17 +0100 [thread overview]
Message-ID: <20190110201217.GH2861@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <d06126a1-1db8-f937-2084-2c1234b6f56f@arm.com>
On Thu, Jan 10, 2019 at 06:25:57PM +0000, James Morse wrote:
> On arm64 if all the RAS and psuedo-NMI patches land, our worst-case interleaving
> jumps to at least 7. The culprit is APEI using spinlocks to protect fixmap slots.
>
> I have an RFC to bump the number of node bits from 2 to 3, but as this is APEI
> four times, it may be preferable to make it use something other than spinlocks.
>
>
> The worst-case order is below. Each one masks those before it:
> 1. process context
> 2. soft-irq
> 3. hard-irq
> 4. psuedo-nmi [0]
> - using the irqchip priorities to configure some IRQs as NMI.
> 5. SError [1]
> - a bit like an asynchronous MCE. ACPI allows this to convey CPER records,
> requiring an APEI call.
> 6&7. SDEI [2]
> - a firmware triggered software interrupt, only its two of them, either of
> which could convey CPER records.
> 8. Synchronous external abort
> - again, similar to MCE. There are systems using this with APEI.
The thing is, everything non-maskable (NMI like) really should not be
using spinlocks at all.
I otherwise have no clue about wth APEI is, but it sounds like horrible
crap ;-)
next prev parent reply other threads:[~2019-01-10 20:12 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-10 8:02 Question about qspinlock nest Zhenzhong Duan
2019-01-10 14:43 ` Waiman Long
2019-01-10 18:25 ` James Morse
2019-01-10 19:23 ` Waiman Long
2019-01-10 20:12 ` Peter Zijlstra [this message]
2019-01-11 18:32 ` James Morse
2019-01-14 13:16 ` Peter Zijlstra
2019-01-14 13:54 ` James Morse
2019-01-14 21:07 ` Waiman Long
2019-01-18 10:02 ` Peter Zijlstra
2019-01-18 10:24 ` Borislav Petkov
2019-01-18 14:50 ` Waiman Long
2019-01-18 20:06 ` Peter Zijlstra
2019-01-18 21:30 ` Waiman Long
[not found] ` <2eca6f60-3e8b-a389-27cb-8adbd9676607@oracle.com>
2019-01-11 9:16 ` Peter Zijlstra
2019-01-11 17:36 ` Borislav Petkov
2019-01-11 16:59 ` Waiman Long
2019-01-10 20:03 ` Peter Zijlstra
2019-01-14 9:25 Zhenzhong Duan
Reply instructions:
You may reply publicly 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:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190110201217.GH2861@worktop.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=james.morse@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=longman@redhat.com \
--cc=srinivas.eeda@oracle.com \
--cc=zhenzhong.duan@oracle.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).