From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934342AbaDKNzy (ORCPT ); Fri, 11 Apr 2014 09:55:54 -0400 Received: from merlin.infradead.org ([205.233.59.134]:39751 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751468AbaDKNzu (ORCPT ); Fri, 11 Apr 2014 09:55:50 -0400 Message-Id: <20140411135218.358900564@infradead.org> User-Agent: quilt/0.60-1 Date: Fri, 11 Apr 2014 15:42:47 +0200 From: Peter Zijlstra To: mingo@kernel.org, tglx@linutronix.de, luto@amacapital.net, nicolas.pitre@linaro.org, daniel.lezcano@linaro.org, peterz@infradead.org, umgwanakikbuti@gmail.com Cc: linux-kernel@vger.kernel.org Subject: [RFC][PATCH 4/8] sched,idle,x86: Switch from TS_POLLING to TIF_POLLING_NRFLAG References: <20140411134243.160989490@infradead.org> Content-Disposition: inline; filename=peterz-ts_polling-x86.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Standardize the idle polling indicator to TIF_POLLING_NRFLAG such that both TIF_NEED_RESCHED and TIF_POLLING_NRFLAG are in the same word. This will allow us, using fetch_or(), to both set NEED_RESCHED and check for POLLING_NRFLAG in a single operation and avoid pointless wakeups. Changing from the non-atomic thread_info::status flags to the atomic thread_info::flags shouldn't be a big issue since most polling state changes were followed/preceded by a full memory barrier anyway. Also, fix up the apm_32 idle function, clearly that was forgotten in the last conversion. The default idle state is !POLLING so just kill the lot. Cc: Thomas Gleixner Cc: Andy Lutomirski Signed-off-by: Peter Zijlstra --- arch/x86/include/asm/thread_info.h | 4 ++-- arch/x86/kernel/apm_32.c | 11 ----------- 2 files changed, 2 insertions(+), 13 deletions(-) --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -83,6 +83,7 @@ struct thread_info { #define TIF_FORK 18 /* ret_from_fork */ #define TIF_NOHZ 19 /* in adaptive nohz mode */ #define TIF_MEMDIE 20 /* is terminating due to OOM killer */ +#define TIF_POLLING_NRFLAG 21 /* idle is polling for TIF_NEED_RESCHED */ #define TIF_IO_BITMAP 22 /* uses I/O bitmap */ #define TIF_FORCED_TF 24 /* true if TF in eflags artificially */ #define TIF_BLOCKSTEP 25 /* set when we want DEBUGCTLMSR_BTF */ @@ -106,6 +107,7 @@ struct thread_info { #define _TIF_IA32 (1 << TIF_IA32) #define _TIF_FORK (1 << TIF_FORK) #define _TIF_NOHZ (1 << TIF_NOHZ) +#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG) #define _TIF_IO_BITMAP (1 << TIF_IO_BITMAP) #define _TIF_FORCED_TF (1 << TIF_FORCED_TF) #define _TIF_BLOCKSTEP (1 << TIF_BLOCKSTEP) @@ -191,8 +193,6 @@ static inline struct thread_info *curren * have to worry about atomic accesses. */ #define TS_COMPAT 0x0002 /* 32bit syscall active (64BIT)*/ -#define TS_POLLING 0x0004 /* idle task polling need_resched, - skip sending interrupt */ #define TS_RESTORE_SIGMASK 0x0008 /* restore signal mask in do_signal() */ #ifndef __ASSEMBLY__ --- a/arch/x86/kernel/apm_32.c +++ b/arch/x86/kernel/apm_32.c @@ -844,21 +844,10 @@ static int apm_do_idle(void) int polling; int err = 0; - polling = !!(current_thread_info()->status & TS_POLLING); - if (polling) { - current_thread_info()->status &= ~TS_POLLING; - /* - * TS_POLLING-cleared state must be visible before we - * test NEED_RESCHED: - */ - smp_mb(); - } if (!need_resched()) { idled = 1; ret = apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax, &err); } - if (polling) - current_thread_info()->status |= TS_POLLING; if (!idled) return 0;