Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 3 Jul 2001 13:56:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 3 Jul 2001 13:55:58 -0400 Received: from panic.ohr.gatech.edu ([130.207.47.194]:24491 "HELO havoc.gtf.org") by vger.kernel.org with SMTP id ; Tue, 3 Jul 2001 13:55:47 -0400 Message-ID: <3B42071F.BD5C8A21@mandrakesoft.com> Date: Tue, 03 Jul 2001 13:55:43 -0400 From: Jeff Garzik Organization: MandrakeSoft X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.6-pre8 i686) X-Accept-Language: en MIME-Version: 1.0 To: Linux Kernel Mailing List Cc: Linus Torvalds , "Grover, Andrew" Subject: ACPI fundamental locking problems Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I used to be pretty excited about ACPI, until today. I was reading through the ACPI spec, to see what was required to obtain the IRQ routing table from AML. Continued reading... until I hit a section talking about the ACPI global lock. events/evxface.c:610:acpi_acquire_global_lock -> events/evmisc.c:337:acpi_ev_acquire_global_lock -> include/platform/acgcc.h:52:ACPI_ACQUIRE_GLOBAL_LOCK My immediate objections are, (a) acgcc.h is re-implementing spinlocks in a non-standard, non-portable, and expensive way, and (b) this entire code path is incredibly expensive. But my fundamental objection is, we are depending on vendors to get locking right in their ACPI tables. And assume by some magic or design that said locking works with whatever unrelated kernel locking is going on. It is my initial belief that a smaller info query interface that can parse useful ACPI would be more effective. For times like suspend/resume where we would want to execute control methods, well, there's always the disasm -> write-small-driver cycle. Who knows if this is a realistics proposed solution. But it really scares me to depend on vendors to get locking right. We'll see what 2.5 will bring... -- Jeff Garzik | "I respect faith, but doubt is Building 1024 | what gives you an education." MandrakeSoft | -- Wilson Mizner - 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/