Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752519Ab3HZWFs (ORCPT ); Mon, 26 Aug 2013 18:05:48 -0400 Received: from a193-30.smtp-out.amazonses.com ([199.255.193.30]:26170 "EHLO a193-30.smtp-out.amazonses.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752233Ab3HZWFo (ORCPT ); Mon, 26 Aug 2013 18:05:44 -0400 X-Greylist: delayed 566 seconds by postgrey-1.27 at vger.kernel.org; Mon, 26 Aug 2013 18:05:44 EDT Message-Id: <00000140bca09c39-5b837fed-8e34-417d-a62d-031f0b5c8107-000000@email.amazonses.com> User-Agent: quilt/0.50-1 Date: Mon, 26 Aug 2013 21:56:17 +0000 From: Christoph Lameter To: Tejun Heo Cc: akpm@linuxfoundation.org, Vineet Gupta Cc: linux-arch@vger.kernel.org Cc: Steven Rostedt Cc: linux-kernel@vger.kernel.org Subject: [guv v2 28/31] arc: Replace __get_cpu_var uses throughout the kernel References: <20130826204351.725357339@linux.com> X-SES-Outgoing: 199.255.193.30 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4477 Lines: 148 __get_cpu_var() is used for multiple purposes in the kernel source. One of them is address calculation via the form &__get_cpu_var(x). This calculates the address for the instance of the percpu variable of the current processor based on an offset. Others usage cases are for storing and retrieving data from the current processors percpu area. __get_cpu_var() can be used as an lvalue when writing data or on the right side of an assignment. __get_cpu_var() is defined as : #define __get_cpu_var(var) (*this_cpu_ptr(&(var))) __get_cpu_var() always only does a address determination. However, store and retrieve operations could use a segment prefix (or global register on other platforms) to avoid the address calculation. this_cpu_write() and this_cpu_read() can directly take an offset into a percpu area and use optimized assembly code to read and write per cpu variables. This patch converts __get_cpu_var into either and explicit address calculation using this_cpu_ptr() or into a use of this_cpu operations that use the offset. Thereby address calcualtions are avoided and less registers are used when code is generated. At the end of the patchset all uses of __get_cpu_var have been removed so the macro is removed too. The patchset includes passes over all arches as well. Once these operations are used throughout then specialized macros can be defined in non -x86 arches as well in order to optimize per cpu access by f.e. using a global register that may be set to the per cpu base. Transformations done to __get_cpu_var() 1. Determine the address of the percpu instance of the current processor. DEFINE_PER_CPU(int, y); int *x = &__get_cpu_var(y); Converts to int *x = this_cpu_ptr(&y); 2. Same as #1 but this time an array structure is involved. DEFINE_PER_CPU(int, y[20]); int *x = __get_cpu_var(y); Converts to int *x = this_cpu_ptr(y); 3. Retrieve the content of the current processors instance of a per cpu variable. DEFINE_PER_CPU(int, u); int x = __get_cpu_var(y) Converts to int x = __this_cpu_read(y); 4. Retrieve the content of a percpu struct DEFINE_PER_CPU(struct mystruct, y); struct mystruct x = __get_cpu_var(y); Converts to memcpy(this_cpu_ptr(&y), x, sizeof(x)); 5. Assignment to a per cpu variable DEFINE_PER_CPU(int, y) __get_cpu_var(y) = x; Converts to this_cpu_write(y, x); 6. Increment/Decrement etc of a per cpu variable DEFINE_PER_CPU(int, y); __get_cpu_var(y)++ Converts to this_cpu_inc(y) Index: linux/arch/arc/kernel/kprobes.c =================================================================== --- linux.orig/arch/arc/kernel/kprobes.c 2013-08-26 13:28:53.000000000 -0500 +++ linux/arch/arc/kernel/kprobes.c 2013-08-26 13:29:19.285103021 -0500 @@ -87,13 +87,13 @@ static void __kprobes save_previous_kpro static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) { - __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; + __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); kcb->kprobe_status = kcb->prev_kprobe.status; } static inline void __kprobes set_current_kprobe(struct kprobe *p) { - __get_cpu_var(current_kprobe) = p; + __this_cpu_write(current_kprobe, p); } static void __kprobes resume_execution(struct kprobe *p, unsigned long addr, @@ -237,7 +237,7 @@ int __kprobes arc_kprobe_handler(unsigne return 1; } else if (kprobe_running()) { - p = __get_cpu_var(current_kprobe); + p = __this_cpu_read(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { setup_singlestep(p, regs); kcb->kprobe_status = KPROBE_HIT_SS; Index: linux/arch/arc/kernel/time.c =================================================================== --- linux.orig/arch/arc/kernel/time.c 2013-08-26 13:28:53.000000000 -0500 +++ linux/arch/arc/kernel/time.c 2013-08-26 13:29:19.285103021 -0500 @@ -206,7 +206,7 @@ static DEFINE_PER_CPU(struct clock_event static irqreturn_t timer_irq_handler(int irq, void *dev_id) { - struct clock_event_device *clk = &__get_cpu_var(arc_clockevent_device); + struct clock_event_device *clk = this_cpu_ptr(&arc_clockevent_device); arc_timer_event_ack(clk->mode == CLOCK_EVT_MODE_PERIODIC); clk->event_handler(clk); -- 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/