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Mon, 23 Sep 2019 14:17:30 -0700 (PDT) Date: Mon, 23 Sep 2019 14:17:27 -0700 From: Matthias Kaehlcke To: Leonard Crestez Subject: Re: [PATCH v6 2/6] PM / devfreq: Move more initialization before registration Message-ID: <20190923211727.GF133864@google.com> References: <0ad496507cd7e6731e46249b1499dfdebe205c16.1569252537.git.leonard.crestez@nxp.com> <20190923181057.GY133864@google.com> <20190923191111.GE133864@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190923_141731_918427_59039EB3 X-CRM114-Status: GOOD ( 28.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Artur =?utf-8?B?xZp3aWdvxYQ=?= , Abel Vesa , Saravana Kannan , "linux-pm@vger.kernel.org" , Viresh Kumar , dl-linux-imx , Krzysztof Kozlowski , Lukasz Luba , Chanwoo Choi , Kyungmin Park , MyungJoo Ham , Alexandre Bailon , Georgi Djakov , "linux-arm-kernel@lists.infradead.org" , Jacky Bai Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 23, 2019 at 07:56:51PM +0000, Leonard Crestez wrote: > On 23.09.2019 22:11, Matthias Kaehlcke wrote: > > On Mon, Sep 23, 2019 at 06:56:28PM +0000, Leonard Crestez wrote: > >> On 23.09.2019 21:11, Matthias Kaehlcke wrote: > >>> On Mon, Sep 23, 2019 at 06:51:05PM +0300, Leonard Crestez wrote: > >>>> In general it is a better to initialize an object before making it > >>>> accessible externally (through device_register). > >>>> > >>>> This makes it possible to avoid relying on locking a partially > >>>> initialized object. > >>>> > >>>> Signed-off-by: Leonard Crestez > >>>> --- > >>>> drivers/devfreq/devfreq.c | 43 +++++++++++++++++++++++---------------- > >>>> 1 file changed, 25 insertions(+), 18 deletions(-) > >>>> > >>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > >>>> index 323d43315d1e..b4d2bfebb140 100644 > >>>> --- a/drivers/devfreq/devfreq.c > >>>> +++ b/drivers/devfreq/devfreq.c > >>>> @@ -587,10 +587,12 @@ static void devfreq_dev_release(struct device *dev) > >>>> mutex_unlock(&devfreq_list_lock); > >>>> > >>>> if (devfreq->profile->exit) > >>>> devfreq->profile->exit(devfreq->dev.parent); > >>>> > >>>> + kfree(devfreq->time_in_state); > >>>> + kfree(devfreq->trans_table); > >>>> mutex_destroy(&devfreq->lock); > >>>> kfree(devfreq); > >>>> } > >>>> > >>>> /** > >>>> @@ -670,44 +672,43 @@ struct devfreq *devfreq_add_device(struct device *dev, > >>>> devfreq->max_freq = devfreq->scaling_max_freq; > >>>> > >>>> devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev); > >>>> atomic_set(&devfreq->suspend_count, 0); > >>>> > >>>> - dev_set_name(&devfreq->dev, "devfreq%d", > >>>> - atomic_inc_return(&devfreq_no)); > >>>> - err = device_register(&devfreq->dev); > >>>> - if (err) { > >>>> - mutex_unlock(&devfreq->lock); > >>>> - put_device(&devfreq->dev); > >>>> - goto err_out; > >>>> - } > >>>> - > >>>> - devfreq->trans_table = devm_kzalloc(&devfreq->dev, > >>>> + devfreq->trans_table = kzalloc( > >>>> array3_size(sizeof(unsigned int), > >>>> devfreq->profile->max_state, > >>>> devfreq->profile->max_state), > >>>> GFP_KERNEL); > >>>> if (!devfreq->trans_table) { > >>>> mutex_unlock(&devfreq->lock); > >>>> err = -ENOMEM; > >>>> - goto err_devfreq; > >>>> + goto err_dev; > >>>> } > >>>> > >>>> - devfreq->time_in_state = devm_kcalloc(&devfreq->dev, > >>>> - devfreq->profile->max_state, > >>>> - sizeof(unsigned long), > >>>> - GFP_KERNEL); > >>>> + devfreq->time_in_state = kcalloc(devfreq->profile->max_state, > >>>> + sizeof(unsigned long), > >>>> + GFP_KERNEL); > >>>> if (!devfreq->time_in_state) { > >>>> mutex_unlock(&devfreq->lock); > >>>> err = -ENOMEM; > >>>> - goto err_devfreq; > >>>> + goto err_dev; > >>>> } > >>>> > >>>> devfreq->last_stat_updated = jiffies; > >>>> > >>>> srcu_init_notifier_head(&devfreq->transition_notifier_list); > >>>> > >>>> + dev_set_name(&devfreq->dev, "devfreq%d", > >>>> + atomic_inc_return(&devfreq_no)); > >>>> + err = device_register(&devfreq->dev); > >>>> + if (err) { > >>>> + mutex_unlock(&devfreq->lock); > >>>> + put_device(&devfreq->dev); > >>>> + goto err_out; > >>> > >>> As per my comment on v5 I think the goto needs to go to 'err_dev'. The > >>> device registration failed, hence devfreq_dev_release() won't be > >>> called to free allocated memory. > >> > >> This code is not modified in the patch, it only shows up as +added > >> because diff got confused but there is an identical -removed chunk > >> higher up. > >> > >> The device_register documentation mentions the following: > >> > >> * NOTE: _Never_ directly free @dev after calling this function, even > >> * if it returned an error! Always use put_device() to give up the > >> * reference initialized in this function instead. > >> > >> Cleanup path then goes like this (from a hacked error in device_add): > >> dump_stack+0xdc/0x144 > >> > >> > >> devfreq_dev_release+0x38/0xc0 > >> > >> > >> device_release+0x34/0x90 > >> > >> > >> kobject_put+0x8c/0x1f0 > >> > >> > >> put_device+0x24/0x30 > >> > >> > >> devfreq_add_device+0x540/0x570 > >> > >> > >> devm_devfreq_add_device+0x60/0xd0 > >> > >> > >> imx_ddrc_probe+0x35c/0x4c8 > > > > Good to know, thanks for the pointer! > > > >> Can I add your "Reviewed-By" for the rest of the series if I fix the nits? > > > > By now you should have it for most patches. For this one: > > > > Reviewed-by: Matthias Kaehlcke > > > > There is one doubt I have left on "PM / devfreq: Add PM QoS support" that I > > posted on v5: > > > > "IIUC you rely on the notifiers being removed by devfreq_dev_release(). > > Does dev_pm_qos_remove_notifier() behave gracefully if the notifier is > > not initialized/added or do we need to use BLOCKING_NOTIFIER_INIT() or > > similar?" > > Sorry for missing that. > > Could you clarify this replying to the thread? Besides that and the > > nits (which are optional to fix) the patch looks good to me. > > The blocking_notifier_head structs are managed by PM QoS inside > dev_pm_qos_constraints_allocate and dev_pm_qos_constraints_destroy. The > devfreq subsystem only registers a notifier_block, that's a > NULL-terminated singly-linked list for which zero-initialization from > kzalloc should be sufficient. Right, thanks for the clarification! > But now that I look at this again I should warn and return NOTIFY_DONE > from devfreq_qos_notifier_call instead of propagating a negative errno. Ack _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel