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From: Peter Zijlstra <peterz@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Travis <travis@sgi.com>, Ingo Molnar <mingo@elte.hu>,
	davej@codemonkey.org.uk, David Miller <davem@davemloft.net>,
	Eric Dumazet <dada1@cosmosbay.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Jack Steiner <steiner@sgi.com>,
	Jeremy Fitzhardinge <jeremy@goop.org>, Jes Sorensen <jes@sgi.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC 07/13] sched: Reduce stack size requirements in kernel/sched.c
Date: Sun, 07 Sep 2008 15:05:50 +0200	[thread overview]
Message-ID: <1220792750.8687.88.camel@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20080907040009.611ac986.akpm@linux-foundation.org>

On Sun, 2008-09-07 at 04:00 -0700, Andrew Morton wrote:
> On Sun, 07 Sep 2008 12:24:47 +0200 Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > get_online_cpus() can sleep, but you just disabled preemption with those
> > get_cpumask_var() horribles!
> 
> make cpu_hotplug.refcount an atomic_t.

A much easier fix is just re-ordering those operations and do the
get_online_cpus() before disabling preemption. But it does indicate this
patch series isn't carefully constructed.

> > Couldn't be arsed to look through the rest, but I really hate this
> > cpumask_ptr() stuff that relies on disabling preemption.
> 
> that's harder to fix ;)

Looking at more patches than just the sched one convinced me more that
this approach isn't a good one. It seems to make code much more
fragile. 

See patch 9, there it was needed to draw out the callgraph in order to
map stuff to these global variables - we're adding global dependencies
to code that didn't have any, increasing complexity.




  reply	other threads:[~2008-09-07 13:09 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-09-06 23:50 [RFC 00/13] smp: reduce stack requirements for genapic send_IPI_mask functions Mike Travis
2008-09-06 23:50 ` [RFC 01/13] smp: modify send_IPI_mask interface to accept cpumask_t pointers Mike Travis
2008-09-06 23:50 ` [RFC 02/13] cpumask: add for_each_online_cpu_mask_nr function Mike Travis
2008-09-06 23:50 ` [RFC 03/13] xen: use new " Mike Travis
2008-09-06 23:50 ` [RFC 04/13] cpumask: add cpumask_ptr operations Mike Travis
2008-09-06 23:50 ` [RFC 05/13] cpumask: add get_cpumask_var debug operations Mike Travis
2008-09-06 23:50 ` [RFC 06/13] genapic: use get_cpumask_var operations for allbutself cpumask_ts Mike Travis
2008-09-06 23:50 ` [RFC 07/13] sched: Reduce stack size requirements in kernel/sched.c Mike Travis
2008-09-07 10:24   ` Peter Zijlstra
2008-09-07 11:00     ` Andrew Morton
2008-09-07 13:05       ` Peter Zijlstra [this message]
2008-09-08 14:56         ` Mike Travis
2008-09-07 20:28       ` Peter Zijlstra
2008-09-08 14:54     ` Mike Travis
2008-09-08 15:05       ` Peter Zijlstra
2008-09-08 18:38         ` Ingo Molnar
2008-09-10 22:47           ` [RFC] CPUMASK: proposal for replacing cpumask_t Mike Travis
2008-09-10 22:53             ` Andi Kleen
2008-09-10 23:33               ` Mike Travis
2008-09-11  5:21                 ` Andi Kleen
2008-09-11  9:00             ` Peter Zijlstra
2008-09-11 15:04               ` Mike Travis
2008-09-12  4:55             ` Rusty Russell
2008-09-12 14:28               ` Mike Travis
2008-09-12 22:02                 ` Rusty Russell
2008-09-12 22:50                   ` Mike Travis
2008-09-12 22:58                     ` H. Peter Anvin
2008-09-06 23:50 ` [RFC 08/13] cpufreq: Reduce stack size requirements in acpi-cpufreq.c Mike Travis
2008-09-06 23:50 ` [RFC 09/13] genapic: reduce stack pressuge in io_apic.c step 1 temp cpumask_ts Mike Travis
2008-09-08 11:01   ` Andi Kleen
2008-09-08 16:03     ` Mike Travis
2008-09-06 23:50 ` [RFC 10/13] genapic: reduce stack pressuge in io_apic.c step 2 internal abi Mike Travis
2008-09-06 23:50 ` [RFC 11/13] genapic: reduce stack pressuge in io_apic.c step 3 target_cpus Mike Travis
2008-09-07  7:55   ` Bert Wesarg
2008-09-07  9:13     ` Ingo Molnar
2008-09-08 15:01       ` Mike Travis
2008-09-08 15:29     ` Mike Travis
2008-09-06 23:50 ` [RFC 12/13] genapic: reduce stack pressuge in io_apic.c step 4 vector allocation Mike Travis
2008-09-06 23:50 ` [RFC 13/13] genapic: reduce stack pressuge in io_apic.c step 5 cpu_mask_to_apicid Mike Travis
2008-09-07  7:36 ` [RFC 00/13] smp: reduce stack requirements for genapic send_IPI_mask functions Ingo Molnar
2008-09-08 15:17   ` Mike Travis

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