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mx.microsoft.com 1; spf=pass smtp.mailfrom=windriver.com; dmarc=pass action=none header.from=windriver.com; dkim=pass header.d=windriver.com; arc=none Authentication-Results: vger.kernel.org; dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=windriver.com; Received: from DM6PR11MB2587.namprd11.prod.outlook.com (2603:10b6:5:c3::16) by DM6PR11MB3563.namprd11.prod.outlook.com (2603:10b6:5:13e::32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4415.13; Wed, 11 Aug 2021 08:32:41 +0000 Received: from DM6PR11MB2587.namprd11.prod.outlook.com ([fe80::8ccc:636b:dcea:7a5d]) by DM6PR11MB2587.namprd11.prod.outlook.com ([fe80::8ccc:636b:dcea:7a5d%5]) with mapi id 15.20.4415.016; Wed, 11 Aug 2021 08:32:41 +0000 Subject: Re: [PATCH] kernel/hung_task.c: Fix a typo in check_hung_task() comment From: Jun Miao Cc: Andrew Morton , Andy Shevchenko , deller@gmx.de, wei.liu@kernel.org, Daniel Bristot de Oliveira , Peter Zijlstra , Linux Kernel Mailing List References: <20210806114049.649909-1-jun.miao@windriver.com> Message-ID: Date: Wed, 11 Aug 2021 16:32:31 +0800 User-Agent: Mozilla/5.0 (X11; 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(no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi,     What about this spelling mistakes ? Thanks Jun On 8/7/21 8:21 PM, Jun Miao wrote: > > On 8/6/21 10:27 PM, Lukas Bulwahn wrote: >> [Please note: This e-mail is from an EXTERNAL e-mail address] >> >> On Fri, Aug 6, 2021 at 1:41 PM Jun Miao wrote: >>> It's "mustn't", not "musn't". Let's fix that. >>> >>> Signed-off-by: Jun Miao >>> --- >>>   kernel/hung_task.c | 2 +- >>>   1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c >>> index 9888e2bc8c76..ea5ba912db06 100644 >>> --- a/kernel/hung_task.c >>> +++ b/kernel/hung_task.c >>> @@ -99,7 +99,7 @@ static void check_hung_task(struct task_struct *t, >>> unsigned long timeout) >>>          /* >>>           * When a freshly created task is scheduled once, changes >>> its state to >>>           * TASK_UNINTERRUPTIBLE without having ever been switched >>> out once, it >>> -        * musn't be checked. >>> +        * mustn't be checked. >> I cannot even parse this comment. >> >> Does "When a freshly created task is scheduled once, changes its state >> to TASK_UNINTERRUPTIBLE" mean "When a freshly created task is >> scheduled once and it changes its state to TASK_UNINTERRUPTIBLE"? >> >> Does this "it must not be checked" read as "it shall not be checked" >> (as in "because if you check it, something goes wrong") or "it is not >> required to be checked" (as in "usually, you need to check it >> (otherwise something goes wrong), but here in this case, you do not >> need to check it, because it cannot go wrong in this case")? >> >> Fixing spelling mistakes is okay, but it is even better to check the >> sentence you are correcting and try to comprehend it. > > Hi Lukas, thanks for your advice from my heart. > > From the context of code: > --- >  90         unsigned long switch_count = t->nvcsw + t->nivcsw; >  91 >  ... ... >  99         /* > 100          * When a freshly created task is scheduled once, changes > its state to > 101          * TASK_UNINTERRUPTIBLE without having ever been switched > out once, it > 102          * mustn't be checked. > 103          */ > 104         if (unlikely(!switch_count)) > 105                 return; > --- > > It should read as "it shall not be checked" (as in "because if you > check it, something goes wrong") > . When create a task and set it as "TASK_UNINTERRUPTIBLE" we don`t > need to check "swtich_count=0". > If check will report a false positive. > > From a history commit cf2592f59c0e, there is a detail explain: >     - the task is freshly created and scheduled >     - it puts its state to TASK_UNINTERRUPTIBLE and is not yet > switched out >     - check_hung_task() scans this task and will report a false > positive because >       t->nvcsw + t->nivcsw == t->last_switch_count == 0 > >     Add a check for such cases. > > Thanks > Jun >> Lukas