From patchwork Wed Jan 3 14:03:17 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Coly Li X-Patchwork-Id: 10142429 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E60AA6035E for ; Wed, 3 Jan 2018 14:03:55 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D66E9290C6 for ; Wed, 3 Jan 2018 14:03:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CB40B290C9; Wed, 3 Jan 2018 14:03:55 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 76E9D290C6 for ; Wed, 3 Jan 2018 14:03:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752628AbeACODy (ORCPT ); Wed, 3 Jan 2018 09:03:54 -0500 Received: from mx2.suse.de ([195.135.220.15]:54958 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752247AbeACODy (ORCPT ); Wed, 3 Jan 2018 09:03:54 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B9E3DACB2; Wed, 3 Jan 2018 14:03:52 +0000 (UTC) From: Coly Li To: linux-bcache@vger.kernel.org Cc: linux-block@vger.kernel.org, mlyle@lyle.org, tang.junhui@zte.com.cn, Coly Li Subject: [PATCH v1 02/10] bcache: set task properly in allocator_wait() Date: Wed, 3 Jan 2018 22:03:17 +0800 Message-Id: <20180103140325.63175-3-colyli@suse.de> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180103140325.63175-1-colyli@suse.de> References: <20180103140325.63175-1-colyli@suse.de> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Kernel thread routine bch_allocator_thread() references macro allocator_wait() to wait for a condition or quit to do_exit() when kthread_should_stop() is true. Macro allocator_wait() has 2 issues in setting task state, let's see its code piece, 284 while (1) { \ 285 set_current_state(TASK_INTERRUPTIBLE); \ 286 if (cond) \ 287 break; \ 288 \ 289 mutex_unlock(&(ca)->set->bucket_lock); \ 290 if (kthread_should_stop()) \ 291 return 0; \ 292 \ 293 schedule(); \ 294 mutex_lock(&(ca)->set->bucket_lock); \ 295 } \ 296 __set_current_state(TASK_RUNNING); \ 1) At line 285, task state is set to TASK_INTERRUPTIBLE, if at line 290 kthread_should_stop() is true, the kernel thread will terminate and return to kernel/kthread.s:kthread(), then calls do_exit() with TASK_INTERRUPTIBLE state. This is not a suggested behavior and a warning message will be reported by might_sleep() in do_exit() code path: "WARNING: do not call blocking ops when !TASK_RUNNING; state=1 set at [xxxx]". 2) Because task state is set to TASK_INTERRUPTIBLE at line 285, when break while-loop the task state has to be set back to TASK_RUNNING at line 296. Indeed it is unncessary, if task state is set to TASK_INTERRUPTIBLE before calling schedule() at line 293, we don't need to set the state back to TASK_RUNNING at line 296 anymore. The reason is, allocator kthread is only woken up by wake_up_process(), this routine makes sure the task state of allocator kthread will be TASK_RUNNING after it returns from schedule() at line 294 (see kernel/sched/core.c:try_to_wake_up() for more detailed information). This patch fixes the above 2 issues by, 1) Setting TASK_INTERRUPTIBLE state just before calling schedule(). 2) Then setting TASK_RUNNING at line 296 is unnecessary, remove it. Signed-off-by: Coly Li Reviewed-by: Michael Lyle --- drivers/md/bcache/alloc.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c index a0cc1bc6d884..48c002faf08d 100644 --- a/drivers/md/bcache/alloc.c +++ b/drivers/md/bcache/alloc.c @@ -282,7 +282,6 @@ static void invalidate_buckets(struct cache *ca) #define allocator_wait(ca, cond) \ do { \ while (1) { \ - set_current_state(TASK_INTERRUPTIBLE); \ if (cond) \ break; \ \ @@ -290,10 +289,10 @@ do { \ if (kthread_should_stop()) \ return 0; \ \ + set_current_state(TASK_INTERRUPTIBLE); \ schedule(); \ mutex_lock(&(ca)->set->bucket_lock); \ } \ - __set_current_state(TASK_RUNNING); \ } while (0) static int bch_allocator_push(struct cache *ca, long bucket)