Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758957Ab3EBBfW (ORCPT ); Wed, 1 May 2013 21:35:22 -0400 Received: from mail-yh0-f73.google.com ([209.85.213.73]:61333 "EHLO mail-yh0-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758466Ab3EBBfQ (ORCPT ); Wed, 1 May 2013 21:35:16 -0400 From: Colin Cross To: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , arve@android.com, Tejun Heo , Oleg Nesterov , Colin Cross , Pavel Machek Subject: [PATCH v2 02/10] freezer: skip waking up tasks with PF_FREEZER_SKIP set Date: Wed, 1 May 2013 18:35:00 -0700 Message-Id: <1367458508-9133-3-git-send-email-ccross@android.com> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1367458508-9133-1-git-send-email-ccross@android.com> References: <1367458508-9133-1-git-send-email-ccross@android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1867 Lines: 50 Android goes through suspend/resume very often (every few seconds when on a busy wifi network with the screen off), and a significant portion of the energy used to go in and out of suspend is spent in the freezer. If a task has called freezer_do_not_count(), don't bother waking it up. If it happens to wake up later it will call freezer_count() and immediately enter the refrigerator. Combined with patches to convert freezable helpers to use freezer_do_not_count() and convert common sites where idle userspace tasks are blocked to use the freezable helpers, this reduces the time and energy required to suspend and resume. Signed-off-by: Colin Cross --- v2: move check to freeze_task() kernel/freezer.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/freezer.c b/kernel/freezer.c index c38893b..8b2afc1 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -110,6 +110,18 @@ bool freeze_task(struct task_struct *p) { unsigned long flags; + /* + * This check can race with freezer_do_not_count, but worst case that + * will result in an extra wakeup being sent to the task. It does not + * race with freezer_count(), the barriers in freezer_count() and + * freezer_should_skip() ensure that either freezer_count() sees + * freezing == true in try_to_freeze() and freezes, or + * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task + * normally. + */ + if (freezer_should_skip(p)) + return false; + spin_lock_irqsave(&freezer_lock, flags); if (!freezing(p) || frozen(p)) { spin_unlock_irqrestore(&freezer_lock, flags); -- 1.8.2.1 -- 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/