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 X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4C6AC43441 for ; Sat, 24 Nov 2018 07:33:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 336032086B for ; Sat, 24 Nov 2018 07:33:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 336032086B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lge.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726706AbeKXSUj (ORCPT ); Sat, 24 Nov 2018 13:20:39 -0500 Received: from lgeamrelo13.lge.com ([156.147.23.53]:44168 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726125AbeKXSUi (ORCPT ); Sat, 24 Nov 2018 13:20:38 -0500 Received: from unknown (HELO lgeamrelo01.lge.com) (156.147.1.125) by 156.147.23.53 with ESMTP; 24 Nov 2018 16:33:07 +0900 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: chanho.min@lge.com Received: from unknown (HELO kernel.lge.com) (165.186.175.97) by 156.147.1.125 with ESMTP; 24 Nov 2018 16:33:07 +0900 X-Original-SENDERIP: 165.186.175.97 X-Original-MAILFROM: chanho.min@lge.com From: Chanho Min To: Jaroslav Kysela , Takashi Iwai , Vinod Koul , Daniel Mentz Cc: linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org, Seungho Park , Jongsung Kim , Wonmin Jung , Jaehyun Kim , Hyonwoo Park , Chanho Min Subject: [PATCH] ALSA: pcm: Fix starvation on down_write_nonblock() Date: Sat, 24 Nov 2018 16:32:43 +0900 Message-Id: <1543044763-31843-1-git-send-email-chanho.min@lge.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit 67ec1072b053 (ALSA: pcm: Fix rwsem deadlock for non-atomic PCM stream) fixes deadlock for non-atomic PCM stream. But, This patch causes antother stuck. If writer is RT thread and reader is a normal thread, the reader thread will be difficult to get scheduled. It may not give chance to release read locks and writer gets stuck for a long time or forever if they are pinned to single cpu. To fix this, The writer gives reader a chance to be scheduled by using the minimum msleep() instaed of spinning. This is for concept, We may need to change the function name and comments or suggest another approach. Signed-off-by: Chanho Min --- sound/core/pcm_native.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 66c90f4..88d4aab 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -96,7 +96,7 @@ static DECLARE_RWSEM(snd_pcm_link_rwsem); static inline void down_write_nonblock(struct rw_semaphore *lock) { while (!down_write_trylock(lock)) - cond_resched(); + msleep(1); } #define PCM_LOCK_DEFAULT 0 -- 2.1.4