All of lore.kernel.org
 help / color / mirror / Atom feed
From: Ingo Molnar <mingo@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Rabin Vincent <rabin@rab.in>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E. McKenney" <paulmck@us.ibm.com>
Subject: Re: qemu:arm test failure due to commit 8053871d0f7f (smp: Fix smp_call_function_single_async() locking)
Date: Sun, 19 Apr 2015 20:01:40 +0200	[thread overview]
Message-ID: <20150419180140.GA8934@gmail.com> (raw)
In-Reply-To: <5533B6D7.9050101@roeck-us.net>


* Guenter Roeck <linux@roeck-us.net> wrote:

> > I _think_ most such callers calling an SMP function call for 
> > offline or out of range CPUs are at minimum racy.
>
> Not really; at least the online cpu part is an absolutely normal use 
> case for qemu-arm.

The problem is that an IPI is attempted to be sent to a non-existent 
CPU AFAICS, right?

> Sure, you can argue that "this isn't the real system", and that 
> qemu-arm should be "fixed", but there are reasons - the emulation is 
> (much) slower if the number of CPUs is set to 4, and not everyone 
> who wants to use qemu has a system with as many CPUs as the emulated 
> system would normally have.

That's all fine and good, but why is an IPI sent to a non-existent 
CPU? It's not like we don't know which CPU is up and down.

Thanks,

	Ingo

  reply	other threads:[~2015-04-19 18:01 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-18 23:23 qemu:arm test failure due to commit 8053871d0f7f (smp: Fix smp_call_function_single_async() locking) Guenter Roeck
2015-04-18 23:40 ` Guenter Roeck
2015-04-19  0:04   ` Linus Torvalds
2015-04-19  0:36     ` Guenter Roeck
2015-04-19  1:56     ` Guenter Roeck
2015-04-19  3:39       ` Rabin Vincent
2015-04-19  4:03         ` Guenter Roeck
     [not found]         ` <CA+55aFw4FSja+VBuCYJ7wLXKVRQZ7w6vOUaUJ4B=FXyBmNkrUg@mail.gmail.com>
2015-04-19  8:56           ` Linus Torvalds
2015-04-19  9:31             ` Ingo Molnar
2015-04-19 14:08               ` Guenter Roeck
2015-04-19 18:01                 ` Ingo Molnar [this message]
2015-04-19 20:34                   ` Linus Torvalds
2015-04-20  5:39                     ` Ingo Molnar
2015-04-20 12:17                       ` Paul E. McKenney
2015-04-20 15:53                       ` Linus Torvalds
2015-04-20 15:41                   ` Rabin Vincent
2015-04-20 10:46                 ` Geert Uytterhoeven
2015-04-20 10:46                   ` Geert Uytterhoeven

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=20150419180140.GA8934@gmail.com \
    --to=mingo@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@roeck-us.net \
    --cc=paulmck@us.ibm.com \
    --cc=peterz@infradead.org \
    --cc=rabin@rab.in \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.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 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.