linux-kernel - [PATCH 0/3] smp: reduce stack requirements for smp_call_function

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Date:	Fri, 05 Sep 2008 14:40:19 -0700
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jack Steiner <steiner@....com>, Jes Sorensen <jes@....com>,
	David Miller <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/3] smp: reduce stack requirements for smp_call_function_mask


  * Cleanup cpumask_t usages in smp_call_function_mask function chain
    to prevent stack overflow problem when NR_CPUS=4096.

  * Reduce the number of passed cpumask_t variables in the following
    call chain for x86_64:

	smp_call_function_mask -->
	    arch_send_call_function_ipi->
		    smp_ops.send_call_func_ipi -->
			    genapic->send_IPI_mask

    Since the smp_call_function_mask() is an EXPORTED function, we
    cannot change it's calling interface for a patch to 2.6.27.

    The smp_ops.send_call_func_ipi interface is internal only and
    has two arch provided functions:

	arch/x86/kernel/smp.c:  .send_call_func_ipi = native_send_call_func_ipi
	arch/x86/xen/smp.c:     .send_call_func_ipi = xen_smp_send_call_function_ipi
	arch/x86/mach-voyager/voyager_smp.c:    (uses native_send_call_func_ipi)

    Therefore modifying the internal interface to use a cpumask_t pointer
    is straight-forward.

    The changes to genapic are much more extensive and are affected by the
    recent additions of the x2apic modes, so they will be done for 2.6.28 only.

Based on 2.6.27-rc5-git6.

Applies to linux-2.6.tip/master (with FUZZ).

Signed-off-by: Mike Travis <travis@....com>
---

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