From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753311AbcADTgQ (ORCPT ); Mon, 4 Jan 2016 14:36:16 -0500 Received: from mail-am1on0083.outbound.protection.outlook.com ([157.56.112.83]:20828 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753102AbcADTf7 (ORCPT ); Mon, 4 Jan 2016 14:35:59 -0500 Authentication-Results: spf=fail (sender IP is 12.216.194.146) smtp.mailfrom=ezchip.com; ezchip.com; dkim=none (message not signed) header.d=none;ezchip.com; dmarc=none action=none header.from=ezchip.com; From: Chris Metcalf To: Gilad Ben Yossef , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Andrew Morton , "Rik van Riel" , Tejun Heo , Frederic Weisbecker , Thomas Gleixner , "Paul E. McKenney" , Christoph Lameter , Viresh Kumar , Catalin Marinas , Will Deacon , Andy Lutomirski , Daniel Lezcano , CC: Chris Metcalf Subject: [PATCH v9 13/13] arm, tile: turn off timer tick for oneshot_stopped state Date: Mon, 4 Jan 2016 14:34:51 -0500 Message-ID: <1451936091-29247-14-git-send-email-cmetcalf@ezchip.com> X-Mailer: git-send-email 2.1.2 In-Reply-To: <1451936091-29247-1-git-send-email-cmetcalf@ezchip.com> References: <1451936091-29247-1-git-send-email-cmetcalf@ezchip.com> X-EOPAttributedMessage: 0 X-Microsoft-Exchange-Diagnostics: 1;DB3FFO11FD026;1:EjhXtRBK/nRu6lQeF9kEvlHXk1XRqmngjKEpTHMeShsgRriYRA7gi8n4EdnWAi2FRQ9C4rpog02tWiA/5CPIaVgUoM3bfdrmxW9m+PC5ZObZyQmHFcEEwT4t54+p4/2k5kboSfQvXF//s3rN6T+OgQTRwcx6Nm9WCXa/LPd122olx/yHre3b43r55Sou7/NXpVzHS/gzsDE/zJFKKiVhT6kwNQZbZipe+dzKGD24st6/TCcnSY+l+4zEGMxEcs7ko2cjFk2kiOIKbkK0UiHtAbaMy70hVOnTGA+EHHXAxpUIHywmuGEck7esN79XjK0L/qZy+BQ0teNtY6kkV51ZajfonKNu72RK/vm0r0Oe1KQR8cXlcnHfJRvkQK59WYnu X-Forefront-Antispam-Report: CIP:12.216.194.146;CTRY:US;IPV:NLI;EFV:NLI;SFV:NSPM;SFS:(10009020)(6009001)(2980300002)(1110001)(1109001)(339900001)(189002)(199003)(2950100001)(50466002)(86362001)(33646002)(92566002)(48376002)(229853001)(36756003)(85426001)(105606002)(87936001)(106466001)(5001970100001)(107886002)(50226001)(189998001)(1096002)(5003940100001)(586003)(1220700001)(5001770100001)(19580405001)(5008740100001)(4001430100002)(42186005)(50986999)(47776003)(4326007)(19580395003)(6806005)(76176999)(104016004)(921003)(1121003);DIR:OUT;SFP:1101;SCL:1;SRVR:DB3PR02MB0427;H:ld-1.internal.tilera.com;FPR:;SPF:Fail;PTR:wb-fw1.tilera.com;MX:1;A:1;LANG:en; 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That function's call to tick_program_event() detects that we are trying to set the expiration to KTIME_MAX and calls clockevents_switch_state() to set the state to ONESHOT_STOPPED, and returns. See commit 8fff52fd5093 ("clockevents: Introduce CLOCK_EVT_STATE_ONESHOT_STOPPED state") for more background. However, by default the internal __clockevents_switch_state() code doesn't have a "set_state_oneshot_stopped" function pointer for the arm_arch_timer or tile clock_event_device structures, so that code returns -ENOSYS, and we end up not setting the state, and more importantly, we don't actually turn off the hardware timer. As a result, the timer tick we were waiting for before is still queued, and fires shortly afterwards, only to discover there was nothing for it to do, at which point it quiesces. The fix is to provide that function pointer field, and like the other function pointers, have it just turn off the timer interrupt. Any call to set a new timer interval will properly re-enable it. This fix avoids a small performance hiccup for regular applications, but for TASK_ISOLATION code, it fixes a potentially serious kernel timer interruption to the time-sensitive application. Signed-off-by: Chris Metcalf --- arch/tile/kernel/time.c | 1 + drivers/clocksource/arm_arch_timer.c | 2 ++ 2 files changed, 3 insertions(+) diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c index 178989e6d3e3..fbedf380d9d4 100644 --- a/arch/tile/kernel/time.c +++ b/arch/tile/kernel/time.c @@ -159,6 +159,7 @@ static DEFINE_PER_CPU(struct clock_event_device, tile_timer) = { .set_next_event = tile_timer_set_next_event, .set_state_shutdown = tile_timer_shutdown, .set_state_oneshot = tile_timer_shutdown, + .set_state_oneshot_stopped = tile_timer_shutdown, .tick_resume = tile_timer_shutdown, }; diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index c64d543d64bf..727a669afb1f 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -288,6 +288,8 @@ static void __arch_timer_setup(unsigned type, } } + clk->set_state_oneshot_stopped = clk->set_state_shutdown; + clk->set_state_shutdown(clk); clockevents_config_and_register(clk, arch_timer_rate, 0xf, 0x7fffffff); -- 2.1.2