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[205.139.110.120]) by gmr-mx.google.com with ESMTPS id c6si198831uan.0.2020.03.12.05.31.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 12 Mar 2020 05:31:25 -0700 (PDT) Received-SPF: pass (google.com: domain of sbrivio@redhat.com designates 205.139.110.120 as permitted sender) client-ip=205.139.110.120; Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=B4AMwQa7; spf=pass (google.com: domain of sbrivio@redhat.com designates 205.139.110.120 as permitted sender) smtp.mailfrom=sbrivio@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584016285; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=atk7dPe9w3xlsO62HVVXQ1ADfhEopAVFLeEvQuA9Hlk=; b=B4AMwQa798p0hSz7gsWGsbBFnFRcQz15tJXhJD7eNbtHiR4t2ibo5sGDfXARMNy1klHokC LCVMhHC9Y88Hm4fzo8jYDIU+4UxJRctcJccdC6wlHrxdJCMlcGptgM64UrRrCY0p9k7IbE sILTeah1yC1ebpcCxjrYa+K+iqF0buQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-244-DqTgAbetMK-866PEkci_3A-1; Thu, 12 Mar 2020 08:31:21 -0400 X-MC-Unique: DqTgAbetMK-866PEkci_3A-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 57732100550D; Thu, 12 Mar 2020 12:31:20 +0000 (UTC) Received: from elisabeth (ovpn-200-18.brq.redhat.com [10.40.200.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6815719C6A; Thu, 12 Mar 2020 12:31:18 +0000 (UTC) Date: Thu, 12 Mar 2020 13:31:12 +0100 From: Stefano Brivio To: Lourdes Pedrajas Cc: outreachy-kernel@googlegroups.com, gregkh@linuxfoundation.org, matthias.bgg@gmail.com Subject: Re: [Outreachy kernel] [PATCH] staging: mt7621-dma: mtk-hsdma: make a variable non-volatile Message-ID: <20200312133112.4f61c60b@elisabeth> In-Reply-To: <20200312121548.6719-1-lu@pplo.net> References: <20200312121548.6719-1-lu@pplo.net> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 12 Mar 2020 13:15:48 +0100 Lourdes Pedrajas wrote: > Change variable declaration volatile unsigned long chan_issued to > unsigned long chan_issued > > Use of volatile is usually wrong: see Documentation/process/volatile-considered-harmful.rst This needs some more details. From that same guide: Patches to remove volatile variables are generally welcome - as long as they come with a justification which shows that the concurrency issues have been properly thought through. so, here you need to investigate what that "volatile" was supposed to achieve, if it is achieved by other means, if some form of locking is needed instead, if we end up in one of the "exception" cases also listed in that guide. -- Stefano