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From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Mukesh Ojha <quic_mojha@quicinc.com>,
	agross@kernel.org, andersson@kernel.org,
	konrad.dybcio@linaro.org, corbet@lwn.net, keescook@chromium.org,
	tony.luck@intel.com, gpiccoli@igalia.com,
	catalin.marinas@arm.com, will@kernel.org,
	krzysztof.kozlowski+dt@linaro.org, robh+dt@kernel.org,
	linus.walleij@linaro.org, linux-gpio@vger.kernel.org,
	srinivas.kandagatla@linaro.org
Cc: linux-arm-msm@vger.kernel.org, linux-remoteproc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH v3 04/18] soc: qcom: Add Qualcomm minidump kernel driver
Date: Tue, 9 May 2023 09:11:32 +0200	[thread overview]
Message-ID: <7777c016-4875-a6c9-cd5e-78c2ac686448@linaro.org> (raw)
In-Reply-To: <e714566e-39b7-d46b-13bd-3c0e20e9f944@quicinc.com>

On 08/05/2023 09:10, Mukesh Ojha wrote:
> 
> 
> On 5/4/2023 10:04 PM, Krzysztof Kozlowski wrote:
>> On 04/05/2023 17:21, Krzysztof Kozlowski wrote:
>>>>>
>>>>>> +	ret = qcom_minidump_init_apss_subsystem(md);
>>>>>> +	if (ret) {
>>>>>> +		dev_err(&pdev->dev, "apss minidump initialization failed: %d\n", ret);
>>>>>> +		goto unlock;
>>>>>> +	}
>>>>>> +
>>>>>> +	__md = md;
>>>>>
>>>>> No. This is a platform device, so it can have multiple instances.
>>>>
>>>> It can have only one instance that is created from SMEM driver probe.
>>>
>>> Anyone can instantiate more of them.... how did you solve it?
>>
>> To clarify - sprinkling more of singletons makes everything tightly
>> coupled, difficult to debug and non-portable. You cannot have two
>> instances, you have to control concurrent initialization by yourself in
>> each of such singletons.
>>
>> I understand sometimes they are unavoidable, for example when this does
>> not map to hardware property. However here you have the parent - smem -
>> which can return you valid instance. Thus you avoid entire problem of
>> file-scope variables.
> 
> I get your point, why one's should avoid file scope variables.
> 
> 
> This is infrastructure driver and will not have multiple instances and 
> even if it happens could be avoided with with the help of global mutex 
> and protect below function which i am already doing at the moment and 

But we do not want global mutexes... so incorrect design is being
improved by more incorrect design.

> fail the other probe if it is already initialized with proper logging..e.g
> 
> "already initialized..."
> 
> 
> ret = qcom_minidump_init_apss_subsystem(md);
> 
> 
> And this will be in-lined with
> 
> /* Pointer to the one and only smem handle */
> static struct qcom_smem *__smem;
> 
> Let me know if you still disagree...and have some other way ?

Why the parent - smem - cannot return every consumer the instance it
has? There will be one smem having only one minidump, so all problems
solved?

Best regards,
Krzysztof


  reply	other threads:[~2023-05-09  7:11 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-03 17:02 [PATCH v3 00/18] Add basic Minidump kernel driver support Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 01/18] remoteproc: qcom: Expand MD_* as MINIDUMP_* Mukesh Ojha
2023-05-04 12:35   ` Krzysztof Kozlowski
2023-05-03 17:02 ` [PATCH v3 02/18] remoteproc: qcom: Move minidump specific data to qcom_minidump.h Mukesh Ojha
2023-05-04 11:38   ` Krzysztof Kozlowski
2023-05-04 11:58     ` Mukesh Ojha
2023-05-04 12:03       ` Krzysztof Kozlowski
2023-05-04 12:26         ` Mukesh Ojha
2023-05-04 12:36           ` Krzysztof Kozlowski
2023-05-04 12:57             ` Mukesh Ojha
2023-05-04 15:16               ` Krzysztof Kozlowski
2023-05-03 17:02 ` [PATCH v3 03/18] docs: qcom: Add qualcomm minidump guide Mukesh Ojha
2023-05-08 10:01   ` Bagas Sanjaya
2023-05-25 16:00     ` Mukesh Ojha
2023-05-13 18:46   ` Randy Dunlap
2023-05-25 15:59     ` Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 04/18] soc: qcom: Add Qualcomm minidump kernel driver Mukesh Ojha
2023-05-04 11:36   ` Krzysztof Kozlowski
2023-05-04 12:38     ` Mukesh Ojha
2023-05-04 15:21       ` Krzysztof Kozlowski
2023-05-04 16:34         ` Krzysztof Kozlowski
2023-05-08  7:10           ` Mukesh Ojha
2023-05-09  7:11             ` Krzysztof Kozlowski [this message]
2023-05-28 11:29               ` Mukesh Ojha
2023-05-14  4:16             ` Trilok Soni
2023-05-05  5:34         ` Mukesh Ojha
2023-06-02 10:43     ` Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 05/18] soc: qcom: minidump: Add pending region registration support Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 06/18] soc: qcom: minidump: Add update region support Mukesh Ojha
2023-05-04 11:40   ` Krzysztof Kozlowski
2023-05-03 17:02 ` [PATCH v3 07/18] arm64: defconfig: Enable Qualcomm minidump driver Mukesh Ojha
2023-05-04 11:23   ` Krzysztof Kozlowski
2023-05-04 11:45     ` Mukesh Ojha
2023-05-04 12:32       ` Krzysztof Kozlowski
2023-05-04 14:43         ` Mukesh Ojha
2023-05-04 15:24           ` Krzysztof Kozlowski
2023-05-03 17:02 ` [PATCH v3 08/18] remoterproc: qcom: refactor to leverage exported minidump symbol Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 09/18] soc: qcom: Add qcom's pstore minidump driver support Mukesh Ojha
2023-05-04 15:35   ` Krzysztof Kozlowski
2023-05-09 16:06   ` Luca Stefani
2023-05-16 20:48     ` Kees Cook
2023-05-03 17:02 ` [PATCH v3 10/18] dt-bindings: reserved-memory: Add qcom,ramoops-minidump binding Mukesh Ojha
2023-05-04 11:22   ` Krzysztof Kozlowski
2023-05-03 17:02 ` [PATCH v3 11/18] arm64: dts: qcom: sm8450: Add Qualcomm ramoops minidump node Mukesh Ojha
2023-05-04  7:14   ` Konrad Dybcio
2023-05-04 11:26   ` Krzysztof Kozlowski
2023-05-03 17:02 ` [PATCH v3 12/18] soc: qcom: Register pstore frontend region with minidump Mukesh Ojha
2023-05-09 15:45   ` Luca Stefani
2023-05-16 20:50   ` Kees Cook
2023-05-03 17:02 ` [PATCH v3 13/18] arm64: defconfig: Enable Qualcomm pstore minidump client driver Mukesh Ojha
2023-05-04 11:23   ` Krzysztof Kozlowski
2023-05-03 17:02 ` [PATCH v3 14/18] firmware: qcom_scm: provide a read-modify-write function Mukesh Ojha
2023-05-18 18:48   ` Trilok Soni
2023-05-03 17:02 ` [PATCH v3 15/18] pinctrl: qcom: Use qcom_scm_io_update_field() Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 16/18] firmware: scm: Modify only the download bits in TCSR register Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 17/18] firmware: qcom_scm: Refactor code to support multiple download mode Mukesh Ojha
2023-05-03 17:02 ` [PATCH v3 18/18] firmware: qcom_scm: Add multiple download mode support Mukesh Ojha
2023-05-04 11:26 ` [PATCH v3 00/18] Add basic Minidump kernel driver support Krzysztof Kozlowski
2023-07-15 22:13 ` (subset) " Bjorn Andersson
2023-07-17  1:15   ` Mathieu Poirier
2023-07-17  8:02     ` Krzysztof Kozlowski
2023-07-17 16:21     ` Bjorn Andersson

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