From: Peter Zijlstra <peterz@infradead.org>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: x86: Inconsistent xAPIC synchronization in arch_irq_work_raise?
Date: Tue, 21 Jan 2014 15:01:13 +0100 [thread overview]
Message-ID: <20140121140113.GL30183@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <52DE6FCE.2050708@siemens.com>
On Tue, Jan 21, 2014 at 02:02:06PM +0100, Jan Kiszka wrote:
> Hi all,
>
> while trying to plug a race in the CPU hotplug code on xAPIC systems, I
> was analyzing IPI transmission patterns. The handlers in
> arch/x86/include/asm/ipi.h first wait for ICR, then send. In contrast,
> arch_irq_work_raise sends the self-IPI directly and then waits. This
> looks inconsistent. Is it intended?
>
> BTW, the races are in wakeup_secondary_cpu_via_init and
> wakeup_secondary_cpu_via_nmi (lacking IRQ disable around ICR accesses).
> There we also send first, then wait for completion. But I guess that is
> due to the code originally only being used during boot. Will send fixes
> for those once the sync pattern is clear to me.
Could be I had no clue what I was doing and copy/pasted the code until
it compiled and ran.
In fact, I've got no clue what an ICR is.
next prev parent reply other threads:[~2014-01-21 14:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-21 13:02 x86: Inconsistent xAPIC synchronization in arch_irq_work_raise? Jan Kiszka
2014-01-21 14:01 ` Peter Zijlstra [this message]
2014-01-21 14:10 ` Ingo Molnar
2014-01-21 14:11 ` Jan Kiszka
2014-01-21 14:34 ` Jan Kiszka
2014-01-21 14:51 ` Peter Zijlstra
2014-01-21 23:20 ` Huang Ying
2014-01-22 18:43 ` Andi Kleen
2014-01-23 18:51 ` Jan Kiszka
2014-01-23 19:11 ` Peter Zijlstra
2014-01-23 19:22 ` Andi Kleen
2014-01-23 19:51 ` Jan Kiszka
2014-01-23 20:17 ` Andi Kleen
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=20140121140113.GL30183@twins.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=hpa@zytor.com \
--cc=jan.kiszka@siemens.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=tglx@linutronix.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.