Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 6 Oct 2002 15:40:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 6 Oct 2002 15:40:55 -0400 Received: from svr-ganmtc-appserv-mgmt.ncf.coxexpress.com ([24.136.46.5]:1542 "EHLO svr-ganmtc-appserv-mgmt.ncf.coxexpress.com") by vger.kernel.org with ESMTP id ; Sun, 6 Oct 2002 15:40:11 -0400 Subject: [PATCH] 2.4: introduce get_cpu() and put_cpu() From: Robert Love To: marcelo@conectiva.com.br Cc: linux-kernel@vger.kernel.org Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Mailer: Ximian Evolution 1.0.8 (1.0.8-10) Date: 06 Oct 2002 15:45:47 -0400 Message-Id: <1033933547.743.4472.camel@phantasy> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2253 Lines: 61 Master Marcelo, In 2.5, it is unsafe to assume the current processor does not change out from under you - thus you must be atomic when calling smp_processor_id(). We introduced the get_cpu() and put_cpu() methods to provide a safe way to access the current processor. This patch back-ports those interfaces to 2.4. Note they do nothing special: get_cpu() simply returns smp_processor_id() and put_cpu() is a no-op. But this will allow easier back-porting from 2.5 and common code-base for drivers, etc. It also does not hurt to be explicit that you do not want the processor to change. As an example, I converted one use of smp_processor_id() to the new interface. Patch is against 2.4.20-pre9, please apply. Robert Love diff -urN linux-2.4.20-pre9/arch/i386/kernel/ioport.c linux/arch/i386/kernel/ioport.c --- linux-2.4.20-pre9/arch/i386/kernel/ioport.c 2002-10-06 14:58:01.000000000 -0400 +++ linux/arch/i386/kernel/ioport.c 2002-10-06 15:21:04.000000000 -0400 @@ -55,12 +55,15 @@ asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on) { struct thread_struct * t = ¤t->thread; - struct tss_struct * tss = init_tss + smp_processor_id(); + struct tss_struct * tss; if ((from + num <= from) || (from + num > IO_BITMAP_SIZE*32)) return -EINVAL; if (turn_on && !capable(CAP_SYS_RAWIO)) return -EPERM; + + tss = init_tss + get_cpu(); + /* * If it's the first ioperm() call in this thread's lifetime, set the * IO bitmap up. ioperm() is much less timing critical than clone(), diff -urN linux-2.4.20-pre9/include/linux/smp.h linux/include/linux/smp.h --- linux-2.4.20-pre9/include/linux/smp.h 2002-10-06 14:57:20.000000000 -0400 +++ linux/include/linux/smp.h 2002-10-06 15:11:00.000000000 -0400 @@ -87,5 +87,9 @@ #define smp_call_function(func,info,retry,wait) ({ 0; }) #define cpu_online_map 1 -#endif -#endif +#endif /* !CONFIG_SMP */ + +#define get_cpu() smp_processor_id() +#define put_cpu() do { } while(0) + +#endif /* __LINUX_SMP_H */ - 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/