Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757548AbZFQV0w (ORCPT ); Wed, 17 Jun 2009 17:26:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753511AbZFQV0o (ORCPT ); Wed, 17 Jun 2009 17:26:44 -0400 Received: from ishtar.tlinx.org ([64.81.245.74]:40629 "EHLO Ishtar.tlinx.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751444AbZFQV0n (ORCPT ); Wed, 17 Jun 2009 17:26:43 -0400 Message-ID: <4A395F80.7060504@tlinx.org> Date: Wed, 17 Jun 2009 14:26:24 -0700 From: Linda Walsh User-Agent: Thunderbird 2.0.0.21 (Windows/20090302) MIME-Version: 1.0 To: LKML Subject: non-standard config in my running distro Default kernel: Effect? X-Stationery: 0.4.9 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1856 Lines: 63 I found what appears to be a "non-standard configuration" in a distro's "Default-SMP", non-Xen kernel, where /proc/config.gz from the running kernel has (I only ran into this doing a diff between a manually constructed config and my running kernel): CONFIG_X86_SMP=y CONFIG_X86_64_SMP=y But does NOT have: CONFIG_USE_GENERIC_SMP_HELPERS=y From what I can tell, this shouldn't be a possible configuration, since CONFIG_X86_SMP should force it to be set to 'y' (not unset). Would this config, (SMP='y', generic_smp_helpers=(undef) ) have any odd effects? Is there a specific "effect" or "feature" one gets by having 'smp=y' but not having the smp_helpers enabled? In my x86_64 arch, the places I see it tested are: block/blk-softirq.c: #if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS) #else /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */ block/blk-sysfs.c: #if defined(CONFIG_USE_GENERIC_SMP_HELPERS) include/linux/smp.h: #ifdef CONFIG_USE_GENERIC_SMP_HELPERS /kernel/Kconfig.hz: def_bool HIGH_RES_TIMERS && (!SMP || USE_GENERIC_SMP_HELPERS) kernel/softirq.c: #ifdef CONFIG_USE_GENERIC_SMP_HELPERS #else /* CONFIG_USE_GENERIC_SMP_HELPERS */ --- It appears it may disable some softirq routines. In include/linux/smp.h, having it undefined would disable the definition of the functions: generic_smp_call_function_single_interrupt, generic_smp_call_function_interrupt, ipi_call_lock, ipi_call_unlock, ipi_call_lock_irq & ipi_call_unlock_irq Does this have any performance or integrity (lost interrupt) implications? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/