From: Thomas Gleixner <tglx@linutronix.de>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: peterz@infradead.org, mingo@kernel.org,
akpm@linux-foundation.org, mgorman@techsingularity.net,
mhocko@kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: x86_64 Question: Are concurrent IPI requests safe?
Date: Wed, 11 May 2016 16:13:50 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.11.1605111611210.3540@nanos> (raw)
In-Reply-To: <201605112219.HEB64012.FLQOFMJOVOtFHS@I-love.SAKURA.ne.jp>
On Wed, 11 May 2016, Tetsuo Handa wrote:
> Thomas Gleixner wrote:
> > On Mon, 9 May 2016, Tetsuo Handa wrote:
> > >
> > > It seems to me that APIC_BASE APIC_ICR APIC_ICR_BUSY are all constant
> > > regardless of calling cpu. Thus, native_apic_mem_read() and
> > > native_apic_mem_write() are using globally shared constant memory
> > > address and __xapic_wait_icr_idle() is making decision based on
> > > globally shared constant memory address. Am I right?
> >
> > No. The APIC address space is per cpu. It's the same address but it's always
> > accessing the local APIC of the cpu on which it is called.
>
> Same address but per CPU magic. I see.
>
> Now, I'm trying with CONFIG_TRACE_IRQFLAGS=y and I can observe that
> irq event stamp shows that hardirqs are disabled for two CPUs when I hit
> this bug. It seems to me that this bug is triggered when two CPUs are
> concurrently calling smp_call_function_many() with wait == true.
> [ 180.434649] hardirqs last enabled at (5324977): [<ffff88007860f990>] 0xffff88007860f990
> [ 180.434650] hardirqs last disabled at (5324978): [<ffff88007860f990>] 0xffff88007860f990
Those addresses are on the stack !?! That makes no sense whatsoever.
> [ 180.434659] task: ffff88007a046440 ti: ffff88007860c000 task.ti: ffff88007860c000
> [ 180.434665] RIP: 0010:[<ffffffff811105bf>] [<ffffffff811105bf>] smp_call_function_many+0x21f/0x2c0
> [ 180.434666] RSP: 0000:ffff88007860f950 EFLAGS: 00000202
And on this CPU interrupt are enabled because the IF bit (9) in EFLAGS is set.
> [ 180.548951] hardirqs last enabled at (601147): [<ffff880078cffa00>] 0xffff880078cffa00
> [ 180.551359] hardirqs last disabled at (601148): [<ffff880078cffa00>] 0xffff880078cffa00
Equally crap.
> [ 180.563802] task: ffff880077ad1940 ti: ffff880078cfc000 task.ti: ffff880078cfc000
> [ 180.565984] RIP: 0010:[<ffffffff811105bf>] [<ffffffff811105bf>] smp_call_function_many+0x21f/0x2c0
> [ 180.568517] RSP: 0000:ffff880078cff9c0 EFLAGS: 00000202
And again interrupts are enabled.
Thanks,
tglx
prev parent reply other threads:[~2016-05-11 14:13 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 10:58 [next-20160506 mm,smp] hang up at csd_lock_wait() from drain_all_pages() Tetsuo Handa
2016-05-09 14:54 ` x86_64 Question: Are concurrent IPI requests safe? Tetsuo Handa
2016-05-09 16:54 ` Thomas Gleixner
2016-05-11 13:19 ` Tetsuo Handa
2016-05-11 13:39 ` Peter Zijlstra
2016-05-11 14:09 ` Tetsuo Handa
2016-05-11 14:33 ` Thomas Gleixner
2016-05-11 15:19 ` Tetsuo Handa
2016-05-11 17:46 ` Peter Zijlstra
2016-05-11 21:56 ` Tetsuo Handa
2016-05-11 14:13 ` Thomas Gleixner [this message]
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=alpine.DEB.2.11.1605111611210.3540@nanos \
--to=tglx@linutronix.de \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@kernel.org \
--cc=mingo@kernel.org \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=peterz@infradead.org \
/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