linux-kernel - Re: mmotm 2009-04-10-02-21 uploaded

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Message-ID: <alpine.LFD.2.00.0904150739100.4132@localhost.localdomain>
Date:	Wed, 15 Apr 2009 07:45:16 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Ali Gholami Rudi <ali@...i.ir>, Ingo Molnar <mingo@...e.hu>,
	Valdis.Kletnieks@...edu, Mike Travis <travis@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	mm-commits@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>,
	Dave Jones <davej@...hat.com>, Len Brown <lenb@...nel.org>
Subject: Re: mmotm 2009-04-10-02-21 uploaded - forkbombed by work_for_cpu



On Wed, 15 Apr 2009, Andrew Morton wrote:
> 
> <stares suspiciously at smp_call_function_many()>
> 
>  * smp_call_function_many(): Run a function on a set of other CPUs.
> 
> "other".  It refuses to call the function on *this* CPU.  Tricky.

.. Argh. And totally different from all the other smp_call_function's. In 
smp_call_function_single(), for example, we literally test

        if (cpu == this_cpu) {
                local_irq_save(flags);
                func(info);
                local_irq_restore(flags);
	}  else {
		.. do the cross-call ..

so I think this is just smp_call_function_many() breakage.

In fact, right now the PPC flush_tlb_page() does that insane dance just 
because of this issue. So yes, there are a few current users, and they 
seem to dislike the bad semantics (the kvm code doesn't care).

Duh duh duh.

		Linus
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