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d="scan'208";a="278345884" Received: from crojewsk-mobl1.ger.corp.intel.com (HELO [10.213.18.70]) ([10.213.18.70]) by fmsmga007.fm.intel.com with ESMTP; 19 Aug 2020 07:54:59 -0700 Subject: Re: [PATCH v4 02/13] ASoC: Intel: catpt: Define DSP operations To: Andy Shevchenko References: <20200812205753.29115-1-cezary.rojewski@intel.com> <20200812205753.29115-3-cezary.rojewski@intel.com> <20200813185129.GB1891694@smile.fi.intel.com> <946fdd80-c89d-ee1b-6eef-e752318b55a6@intel.com> <20200818115050.GI1891694@smile.fi.intel.com> <9a733e30-8d44-edf7-1bae-5b6f935628d2@intel.com> <20200819142128.GP1891694@smile.fi.intel.com> From: Cezary Rojewski Message-ID: <3ce135e9-c466-b6c7-9d7f-88c4fe6aab14@intel.com> Date: Wed, 19 Aug 2020 16:54:58 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200819142128.GP1891694@smile.fi.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Cc: pierre-louis.bossart@linux.intel.com, alsa-devel@alsa-project.org, filip.kaczmarski@intel.com, harshapriya.n@intel.com, marcin.barlik@intel.com, zwisler@google.com, lgirdwood@gmail.com, tiwai@suse.com, filip.proborszcz@intel.com, broonie@kernel.org, amadeuszx.slawinski@linux.intel.com, michal.wasko@intel.com, cujomalainey@chromium.org, krzysztof.hejmowski@intel.com, ppapierkowski@habana.ai, vamshi.krishna.gopal@intel.com X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On 2020-08-19 4:21 PM, Andy Shevchenko wrote: > On Wed, Aug 19, 2020 at 03:46:30PM +0200, Cezary Rojewski wrote: >> On 2020-08-18 1:50 PM, Andy Shevchenko wrote: >>> On Mon, Aug 17, 2020 at 01:12:01PM +0200, Cezary Rojewski wrote: >>>> On 2020-08-13 8:51 PM, Andy Shevchenko wrote: >>>>> On Wed, Aug 12, 2020 at 10:57:42PM +0200, Cezary Rojewski wrote: >>>>>> + bool lp; >>>>>> + >>>>>> + if (list_empty(&cdev->stream_list)) >>>>>> + return catpt_dsp_select_lpclock(cdev, true, true); >>>>>> + >>>>>> + lp = true; >>>>>> + list_for_each_entry(stream, &cdev->stream_list, node) { >>>>>> + if (stream->prepared) { >>>>>> + lp = false; >>>>>> + break; >>>>>> + } >>>>>> + } >>>>>> + >>>>>> + return catpt_dsp_select_lpclock(cdev, lp, true); >>>>> >>>>> Seems too much duplication. >>>>> >>>>> struct catpt_stream_runtime *stream; >>>>> >>>>> list_for_each_entry(stream, &cdev->stream_list, node) { >>>>> if (stream->prepared) >>>>> return catpt_dsp_select_lpclock(cdev, false, true); >>>>> } >>>>> >>>>> return catpt_dsp_select_lpclock(cdev, true, true); >>>>> >>>>> >>>>> Better? >>>> >>>> list_first_entry (part of list_for_each_entry) expects list to be non-empty. >>>> ->streal_list may be empty when invoking catpt_dsp_update_lpclock(). >>> >>> I didn't get this. Can you point out where is exactly problematic place? >>> >> >> list_for_each_entry makes use of list_first_entry when initializing 'pos' >> index variable. > > Correct. > >> Documentation for list_first_entry reads: "Note, that list >> is expected to be not empty" > > Correct. > >> so I'm validating list's status before moving >> on to the loop as stream_list may be empty when catpt_dsp_update_lpclock() >> gets called. > > But here you missed the second part of the for-loop, i.e. exit conditional. > > If your assumption (that list_for_each_*() is not empty-safe) is correct, > it would be disaster in global kernel source level. > We want no disasters here : ) safety-out. Ack.