From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 504D0C433F5 for ; Wed, 6 Oct 2021 11:13:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A085610FC for ; Wed, 6 Oct 2021 11:13:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238553AbhJFLPi (ORCPT ); Wed, 6 Oct 2021 07:15:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:38834 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238592AbhJFLPD (ORCPT ); Wed, 6 Oct 2021 07:15:03 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E4ABD611B0; Wed, 6 Oct 2021 11:13:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633518791; bh=14utBTnVu/9mbipzCGXIpaBWLjpPIZQ3PDlawEedbKE=; h=From:To:Cc:Subject:Date:From; b=SKktJo6/H7SIgQevFoDdBLbcxWecVdu0yUXfPqwSNJ7w9Lx28KloE0rw+gB7SKC4L fcTiuYLIzNYnSUdoKl5tvE8WOOig+rcWn67ZrR7Hu5nipeUTVK6Cbu/VZ7uMDsE95m oRWkgN1w1571tWJuXln5d26Kgc5aWYPZfI1SvmCtlBXMpWJBhp7gI2GvVKGlsG1iHf yKO3FzlR4qQ8bWoud1tvKWkz793F/N9kl4a94f9edtClBlLRvDAZ9OQl8XaincSg43 0NeK+zzxKGBIbkeIuDwrL4L24aML4wJ7qQZ5/W1e20NF8N0sxxulCjCT5+u4UAbX+3 iFhCf8jpjADYg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Thomas Gleixner , alsa-devel@alsa-project.org, Takashi Iwai , Jaroslav Kysela , Takashi Iwai , Sasha Levin Subject: [PATCH MANUALSEL 4.9] ALSA: pcsp: Make hrtimer forwarding more robust Date: Wed, 6 Oct 2021 07:13:08 -0400 Message-Id: <20211006111309.264510-1-sashal@kernel.org> X-Mailer: git-send-email 2.33.0 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner [ Upstream commit f2ff7147c6834f244b8ce636b12e71a3bd044629 ] The hrtimer callback pcsp_do_timer() prepares rearming of the timer with hrtimer_forward(). hrtimer_forward() is intended to provide a mechanism to forward the expiry time of the hrtimer by a multiple of the period argument so that the expiry time greater than the time provided in the 'now' argument. pcsp_do_timer() invokes hrtimer_forward() with the current timer expiry time as 'now' argument. That's providing a periodic timer expiry, but is not really robust when the timer callback is delayed so that the resulting new expiry time is already in the past which causes the callback to be invoked immediately again. If the timer is delayed then the back to back invocation is not really making it better than skipping the missed periods. Sound is distorted in any case. Use hrtimer_forward_now() which ensures that the next expiry is in the future. This prevents hogging the CPU in the timer expiry code and allows later on to remove hrtimer_forward() from the public interfaces. Signed-off-by: Thomas Gleixner Cc: alsa-devel@alsa-project.org Cc: Takashi Iwai Cc: Jaroslav Kysela Link: https://lore.kernel.org/r/20210923153339.623208460@linutronix.de Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/drivers/pcsp/pcsp_lib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sound/drivers/pcsp/pcsp_lib.c b/sound/drivers/pcsp/pcsp_lib.c index 3689f5f6be64..3766624c018f 100644 --- a/sound/drivers/pcsp/pcsp_lib.c +++ b/sound/drivers/pcsp/pcsp_lib.c @@ -144,7 +144,7 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle) if (pointer_update) pcsp_pointer_update(chip); - hrtimer_forward(handle, hrtimer_get_expires(handle), ns_to_ktime(ns)); + hrtimer_forward_now(handle, ns_to_ktime(ns)); return HRTIMER_RESTART; } -- 2.33.0