| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Fri, 2 Dec 2022 09:17:44 +0800
From: "Aiqun(Maria) Yu" <quic_aiquny@...cinc.com>
To: Mathieu Poirier <mathieu.poirier@...aro.org>
CC: Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>,
<linux-remoteproc@...r.kernel.org>,
<linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<quic_clew@...cinc.com>
Subject: Re: [PATCH v4] remoteproc: core: do pm relax when in RPROC_OFFLINE
On 12/2/2022 7:00 AM, Mathieu Poirier wrote:
> On Mon, Nov 28, 2022 at 10:18:28AM +0800, Aiqun(Maria) Yu wrote:
>> On 11/26/2022 2:37 AM, Mathieu Poirier wrote:
>>> On Fri, Nov 18, 2022 at 11:52:46AM -0700, Mathieu Poirier wrote:
>>>> On Tue, Nov 15, 2022 at 09:30:58AM +0800, Aiqun(Maria) Yu wrote:
>>>>> Hi,
>>>>>
>>>>> On 11/15/2022 5:18 AM, Mathieu Poirier wrote:
>>>>>> On Fri, Nov 11, 2022 at 08:52:11AM +0800, Aiqun(Maria) Yu wrote:
>>>>>>> On 11/11/2022 4:50 AM, Mathieu Poirier wrote:
>>>>>>>> I had a couple of good discussions with our power management expert
>>>>>>>> and even then, the way forward isn't as clear as I would have liked.
>>>>>>>> I am currently travelling and as such don't have the required time to
>>>>>>>> go into greater details, something I will be doing next week.
>>>>>>>>
>>>>>>> Thx Mathieu for the info updated.
>>>>>>> I'll wait for your update next week then.
>>>>>>> let me know any initial questions that you have, perhaps I can also discuss
>>>>>>> that with our power team at the same time.
>>>>>>
>>>>>> The problem is to determine exactly what the WQ_FREEZABLE flag does to the
>>>>>> rproc_recovery_wq workueue. The documentation [1] indicate that work items on the WQ are
>>>>>> drained before the system is suspended. What I understand from this is that if
>>>>>> two work items are queued and one is executing at the time a system suspend is
>>>>>> initiated, all three items will be executed before the system is allowed to be
>>>>>> suspended. _If_ that is the case, there would not be a need to call
>>>>>> pm_stay_awake() and pm_relax() at all.
>>>>>>
>>>>>> On the other hand, the PM resource I spoke to thought that in reality things
>>>>>> don't happen that way. Taking the same above scenario where 2 work items are
>>>>>> queued and one is executing at the time of the suspend, only the work item that
>>>>>> is executing will be allowed to execute to completion before the system is
>>>>>> suspended. The remaining two items that were queued will not execute.
>>>>>>
>>>>>> If that is the case then we do need to call pm_stay_awake() and pm_relax(), and
>>>>>> find another strategy to fix this situation.
>>>>>>
>>>>>> Until we have a clear view of how the WQ_FREEZABLE flag works, we won't be able
>>>>>> to move forward with this patchset. Unfortunately, I currently do not have the
>>>>>> time to look into this.
>>>>> I had a check on the WQ_FREEZABLE flag, here is my understanding:
>>>>>
>>>>> when the interrupt happened, it still need pm_stay_awake to make sure
>>>>> queue_work action can active the work instead of susepend the device.
>>>>>
>>>>> 1. If WQ_FREEZABLE, pwq->max_active = 0; // maximum number of in-flight
>>>>> work items is set to 0.
>>>>>
>>>>> [1].
>>>>> https://elixir.bootlin.com/linux/v6.1-rc4/source/kernel/workqueue.c#L3748
>>>>>
>>>>> 2. If WQ_FREEZABLE, will only check pwq->nr_active to see if there is still
>>>>> freeze_workqueues_busy.
>>>>> [2].
>>>>> https://elixir.bootlin.com/linux/v6.1-rc4/source/kernel/workqueue.c#L5270
>>>>>
>>>>> 3. When in queue_work, if max_active is 0, when do queue_work it will not
>>>>> actually active the work.
>>>>> [3].
>>>>> https://elixir.bootlin.com/linux/v6.1-rc4/source/kernel/workqueue.c#L1418
>>>>>
>>>>> for the current issue, the work is already complete and forget to set
>>>>> pm_relax in some condition that make the system cannot be suspended.
>>>>
>>>> What you have above does not describe what happens to work already queue to a
>>>> WQ_FREEZABLE workqueue when the system gets suspended, and that is the most
>>>> important thing.
>>>>
>>>> I ended up doing that investigation myself and found the documentation on
>>>> WQ_FREEZABLE seems to be accurate. I am still discussing this with the Linaro
>>>> power management team and will get back to you when we reach a conclusion.
>>>>
>>>
>>> I finally have time to get back to this problem...
>>>
>>> As I reported above I went down to the bottom of how WQ_FREEZABLE workqueues
>>> work. The conclusion of that research is that _any_ work, queued or currently
>>> executing, will finish before the system is suspended. As such, as soon as
>>> queue_work() returns in rproc_report_crash(), you can be guaranteed what was
>>> just queued will be executed. Therefore, calling pm_stay_awake() in
>>> rproc_report_crash() and pm_relax() in rproc_crash_handler_work() should not be
>>> needed because the system will not suspend for as long as there is work to be
>>> done by the freezable worqueues.
>>>
>> The problem is when crash interrupt happened in a later point(after
>> freeze_kernel_thread), the queue_work will result with the state of
>> WORK_STRUCT_INACTIVE and insert to inactive_works.
>> And this is the senario that pm_stay_awake wanted to address inside the
>> interrupt handler call.
>>
>> refer to:
>> [1]
>> https://elixir.bootlin.com/linux/v6.1-rc4/source/kernel/workqueue.c#L1512
>>
>> the current suspend simple flow can be:
>>
>> +-+-------------------+
>> | freeze_processes |
>> +----------+----------+
>> |
>> |
>> +-----------|-----------+
>> | freeze_kernel_thread |
>> +-----------+-----------+
>> |
>> +-+--------|----------+
>> | device_suspend |
>> +----------|----------+
>> |
>> |
>> +-----------+-----------+
>> | pm_wakeup_pending |
>> +-----------|-----------+
>> |
>> |
>> +-----------------+-------------------+
>> | suspend_ops->enter (machine suspend)|
>> +-------------------------------------+
>>
>>
>> refer to:
>> suspend_prepare -> suspend_freeze_processes -->freeze_processes and
>> freeze_kernel_threads
>>
>>
>>
>> refer to:
>>
>> suspend_devices_and_enter -->
>> dpm_suspend_start -> dpm_suspend --> device_suspend --> device suspend
>> callbacks
>> suspend_enter -->dpm_suspend_late-->device_suspend_late
>>
>> [2]
>> https://elixir.bootlin.com/linux/v6.1-rc4/source/kernel/power/suspend.c#L582
>>
>>> I don't have details on what Rishabh - the author of the patch that added the
>>> calls - was facing but based on the my understanding of freezable workqueues, it
>>> seem to have been the wrong solution.
>> In my opinion, the freezable workqueues are in the right solution. It only
>> protect for the system freeze state.
>> While if we want the crash interrupt to be handled to prevent current
>> suspend process, it still need to deal with other suspend state to machin
>> suspend senarios.
>> Typical example can be before disable the device interrupt in device suspend
>> callbacks, it will flush the necessary workqueues.
>>
>> while in our case, since the crash handler will invoke a subsystem restart
>> process which reply on user thread uevent firmware loaders, so it need to
>> abort the suspend process with pm_stay_awake called.
>>
>> So in a word, pm_stay_awake is necessary per my understanding.
>>
>
> I see your point - thanks for being perseverant. What is important to
> understand is that pm_stay_awake() can stop and reverse the suspend process that
> is currently underway.
Thx for the understanding as well.
Perseverant in most of time can be a win win result.
>
> With the code you had for V4 in mind, I suggest to modify
> rproc_crash_handler_work() to be:
>
> ...
> ...
> ...
>
> if (rproc->state == RPROC_CRASHED) {
> /* handle only the first crash detected */
> mutex_unlock(&rproc->lock);
> return;
> }
>
> if (rproc->state == RPROC_OFFLINE) {
> /* The remote processor is offline, no need to recover anything */
> mutex_unlock(&rproc->lock);
> goto out;
> }
>
> ...
> ...
> ...
>
> out:
> pm_relax();
> > Do you think that will work for you?
>
This is good.
Also, alloc_ordered_workqueue instead of alloc_workqueue is suggested in
the same patch.
Because with alloc_ordered_workqueue, only 1 work will be actively
executing. It is to avoid unnecessary contentions which have multi crash
work executing at the same time.
I will upload new patchset for discussion.
>
>>>
>>> Until we have a clear vision on what Rishabh was trying to fix, nothing in that
>>> area will be changing. I suggest you touch base with him and sort it out. If
>>> that is not possible then calls to pm_stay_awake() and pm_relax() should be
>>> removed.
>>>
>>>>>
>>>>>>
>>>>>> If you want to take on this investigation, keep in mind that any conclusion will
>>>>>> need to be backed by a proof. That can be debug messages on a console output or
>>>>>> a code reference in the workqueue core.
>>>>>>
>>>>>> [1]. https://elixir.bootlin.com/linux/v6.1-rc4/source/Documentation/core-api/workqueue.rst#L184
>>>>>>
>>>>>>
>>>>>>>> On Sun, 6 Nov 2022 at 18:14, Aiqun(Maria) Yu <quic_aiquny@...cinc.com> wrote:
>>>>>>>>>
>>>>>>>>> Hi,
>>>>>>>>> On 11/4/2022 11:59 PM, Mathieu Poirier wrote:
>>>>>>>>>> On Thu, Nov 03, 2022 at 10:03:49AM +0800, Aiqun(Maria) Yu wrote:
>>>>>>>>>>> On 11/3/2022 2:03 AM, Mathieu Poirier wrote:
>>>>>>>>>>>> On Wed, Nov 02, 2022 at 06:53:49PM +0800, Aiqun(Maria) Yu wrote:
>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Let me think about this carefully.
>>>>>>>>>>>>>
>>>>>>>>>>>>> When in RPROC_RECOVERY_FAIL case we want to re-do the recovery process again
>>>>>>>>>>>>> or just leave the pm_relax?
>>>>>>>>>>>>
>>>>>>>>>>>> Neither.
>>>>>>>>>>>>
>>>>>>>>>>>> When a recovery fail we don't want to call pm_relax(). The code in
>>>>>>>>>>>> rproc_crash_handler_work() becomes:
>>>>>>>>>>>>
>>>>>>>>>>>> if (rproc->state == RPROC_OFFLINE) {
>>>>>>>>>>>> /* We have raced with rproc_shutdown() */
>>>>>>>>>>>> pm_relax()
>>>>>>>>>>>> mutex_unlock(&rproc->lock);
>>>>>>>>>>>> return;
>>>>>>>>>>>> }
>>>>>>>>>>>>
>>>>>>>>>>>> if (rproc->state == RPROC_CRASHED ||
>>>>>>>>>>>> rproc->state == RPROC_RECOVERY_FAILED) {
>>>>>>>>>>>> /* handle only the first crash detected */
>>>>>>>>>>>> mutex_unlock(&rproc->lock);
>>>>>>>>>>>> return;
>>>>>>>>>>>> }
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> RPROC_RECOVERY_FAILED gets set in rproc_boot_recovery() if request_firmware() or
>>>>>>>>>>>> rproc_start() fail. Function rproc_trigger_recovery() needs to allow for the
>>>>>>>>>>>> recovery the the remote processor is in RPROC_RECOVERY_FAILED state. As such
>>>>>>>>>>>> the condition becomes:
>>>>>>>>>>>>
>>>>>>>>>>>> /* State could have changed before we got the mutex */
>>>>>>>>>>>> if (rproc->state != RPROC_CRASHED &&
>>>>>>>>>>>> rproc->state != RPROC_RECOVERY_FAILED)
>>>>>>>>>>>> goto unlock_mutex;
>>>>>>>>>>>>
>>>>>>>>>>>> Start with that and we can look at corner cases (if some exists) with a fresh
>>>>>>>>>>>> patchset. Note that I have not addressed the attach/detach() scenario in the
>>>>>>>>>>>> above.
>>>>>>>>>>>
>>>>>>>>>>> If we didn't deal with the recovery failed case with correct pm_relax call,
>>>>>>>>>>> it may left the device in a state that cannot enter to suspend state.
>>>>>>>>>>
>>>>>>>>>> That is what I am looking for. We don't want to give the impression that
>>>>>>>>>> everything is fine by allowing the device to suspend. If the remote processor
>>>>>>>>>> can't be recovered than it needs to be dealth with.
>>>>>>>>> For the normal recovery failed case, it still need to do pm_relax to not
>>>>>>>>> prevent the device goes to suspend. It is what in normal recovery failed
>>>>>>>>> case we do in rproc_crash_handler_work as well.
>>>>>>>>> rproc_crash_handler_work will not check the result of the
>>>>>>>>> rproc_trigger_recovery return value, and will always do pm_relax.
>>>>>>>>>
>>>>>>>>> For current conconrency cornor case as well, it is better to consistant
>>>>>>>>> with the current design of recovery fail senarios in normal cases.
>>>>>>>>>
>>>>>>>>> I personally agree that we shouldn't do nothing when it is a
>>>>>>>>> RPROC_RECOVERY_FAILED senario when it is in rproc_crash_handler_work
>>>>>>>>> check, because it maybe crash happened when it is trying to do the recovery.
>>>>>>>>> So I suggested to do a continue try of trigger recovery again instead of
>>>>>>>>> doing nothing and bail out if it is a RPROC_RECOVERY_FAILED state.
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> Because first PROC_RECOVERY_FAIL case cannot ensure it have pm_relax called
>>>>>>>>>>> before the second crash handler call pm_stay_awake or not.
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I've been thinking about that part. I don't think adding a wake_count to
>>>>>>>>>> control calls to pm_stay_awake()/pm_relax() is the best way to go. There is a
>>>>>>>>>> similar count happening in the PM runtime subsystem and that is what we should
>>>>>>>>>> be using. I have asked a power management expert at Linaro for guidance with
>>>>>>>>>> this matter. I should be able to get back to you with a way forward by the end
>>>>>>>>>> of next week.
>>>>>>>>>>
>>>>>>>>> Thx for the specific date provided as well. I will wait until your reply
>>>>>>>>> for next patchset then.
>>>>>>>>>
>>>>>>>>>>> So, What about the atomic count along with pm_relax and pm_stay_awake ?
>>>>>>>>>>>
>>>>>>>>>>> struct rproc{
>>>>>>>>>>> ...
>>>>>>>>>>> atomic_t wake_count;
>>>>>>>>>>> ...
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>> rproc_pm_stay_awake()
>>>>>>>>>>> {
>>>>>>>>>>> atomic_inc(&wake_count);
>>>>>>>>>>> pm_stay_awake();
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>> rproc_pm_relax()
>>>>>>>>>>> {
>>>>>>>>>>> if (atomic_dec_return(&wake_count) == 0)
>>>>>>>>>>> pm_stay_awake();
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>> can refer code like:
>>>>>>>>>>>
>>>>>>>>>>> rproc_report_crash()
>>>>>>>>>>> {
>>>>>>>>>>> ...
>>>>>>>>>>> rproc_pm_stay_awake();
>>>>>>>>>>> queue_work();
>>>>>>>>>>> ...
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>> rproc_crash_handler_work()
>>>>>>>>>>> {
>>>>>>>>>>> ...
>>>>>>>>>>> if (rproc->state == RPROC_OFFLINE || rproc->state == RPROC_CRASHED) {
>>>>>>>>>>> /* We have raced with rproc_shutdown() */
>>>>>>>>>>> rproc_pm_relax();
>>>>>>>>>>> mutex_unlock(&rproc->lock);
>>>>>>>>>>> return;
>>>>>>>>>>> }
>>>>>>>>>>> ...
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>> Mathieu
>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> recovery fail case 1:
>>>>>>>>>>>>> | |firstcrash interrupt issued
>>>>>>>>>>>>> | second crashed interrupt issued | rproc_report_crash()
>>>>>>>>>>>>> | rproc_report_crash() | pm_stay_awake()
>>>>>>>>>>>>> | pm_stay_awake() | queue_work()
>>>>>>>>>>>>> | queue_work() |rproc_crash_handler_work()
>>>>>>>>>>>>> | |mutex_lock(&rproc->lock);
>>>>>>>>>>>>> | |rproc_stop()
>>>>>>>>>>>>> |rproc_crash_handler_work() |rproc->state = RPROC_OFFLINE;
>>>>>>>>>>>>> | |RPROC_RECOVERY_FAIL //new
>>>>>>>>>>>>> | |mutex_unlock(&rproc->lock);
>>>>>>>>>>>>> |mutex_lock(&rproc->lock); |pm_relax()
>>>>>>>>>>>>> |if (rproc->state == RPROC_OFFLINE) |
>>>>>>>>>>>>> |return // shouldn't do pm_relax if RPROC_RECOVERY_FAIL? |
>>>>>>>>>>>>> |mutex_unlock(&rproc->lock); |
>>>>>>>>>>>>> | |
>>>>>>>>>>>>> | |
>>>>>>>>>>>>> | |
>>>>>>>>>>>>>
>>>>>>>>>>>>> recovery fail case 2:
>>>>>>>>>>>>> | |firstcrash interrupt issued
>>>>>>>>>>>>> | | rproc_report_crash()
>>>>>>>>>>>>> | | pm_stay_awake()
>>>>>>>>>>>>> | | queue_work()
>>>>>>>>>>>>> | |rproc_crash_handler_work()
>>>>>>>>>>>>> | |mutex_lock(&rproc->lock);
>>>>>>>>>>>>> | |rproc_stop()
>>>>>>>>>>>>> | |rproc->state = RPROC_OFFLINE;
>>>>>>>>>>>>> | |RPROC_RECOVERY_FAIL //new
>>>>>>>>>>>>> | |mutex_unlock(&rproc->lock);
>>>>>>>>>>>>> | |pm_relax()
>>>>>>>>>>>>> |
>>>>>>>>>>>>> | second crashed interrupt issued |
>>>>>>>>>>>>> | rproc_report_crash() |
>>>>>>>>>>>>> | pm_stay_awake() |
>>>>>>>>>>>>> | queue_work() |
>>>>>>>>>>>>> |pm_stay_awake()
>>>>>>>>>>>>> |mutex_lock(&rproc->lock);
>>>>>>>>>>>>> |if (rproc->state == RPROC_OFFLINE) |
>>>>>>>>>>>>> |return // still need do pm_relax if RPROC_RECOVERY_FAIL? |
>>>>>>>>>>>>> |mutex_unlock(&rproc->lock); |
>>>>>>>>>>>>> | |
>>>>>>>>>>>>> | |
>>>>>>>>>>>>> | |
>>>>>>>>>>>>>
>>>>>>>>>>>>> Maybe I can have:
>>>>>>>>>>>>> 1. the pm_stay_awake and pm_relax with count based and call with paired for
>>>>>>>>>>>>> fix current concurency issue.
>>>>>>>>>>>>> 2. RPROC_RECOVERY_FAIL can be another patch for continue try to do recovery
>>>>>>>>>>>>> work.
>>>>>>>>>>>>> 3. handle RPROC_DETACHED case.
>>>>>>>>>>>>>
>>>>>>>>>>>>> On 11/2/2022 4:11 AM, Mathieu Poirier wrote:
>>>>>>>>>>>>>> On Fri, 28 Oct 2022 at 09:31, Arnaud POULIQUEN
>>>>>>>>>>>>>> <arnaud.pouliquen@...s.st.com> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On 10/24/22 05:17, Aiqun(Maria) Yu wrote:
>>>>>>>>>>>>>>>> On 10/22/2022 3:34 AM, Mathieu Poirier wrote:
>>>>>>>>>>>>>>>>> On Wed, 19 Oct 2022 at 23:52, Aiqun(Maria) Yu <quic_aiquny@...cinc.com> wrote:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> On 10/14/2022 2:03 AM, Mathieu Poirier wrote:
>>>>>>>>>>>>>>>>>>> On Thu, Oct 13, 2022 at 11:34:42AM -0600, Mathieu Poirier wrote:
>>>>>>>>>>>>>>>>>>>> On Thu, Oct 13, 2022 at 09:40:09AM +0800, Aiqun(Maria) Yu wrote:
>>>>>>>>>>>>>>>>>>>>> Hi Mathieu,
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> On 10/13/2022 4:43 AM, Mathieu Poirier wrote:
>>>>>>>>>>>>>>>>>>>>>> Please add what has changed from one version to another, either in a cover
>>>>>>>>>>>>>>>>>>>>>> letter or after the "Signed-off-by". There are many examples on how to
>>>>>>>>>>>>>>>>>>>>>> do that
>>>>>>>>>>>>>>>>>>>>>> on the mailing list.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Thx for the information, will take a note and benefit for next time.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> On Fri, Sep 16, 2022 at 03:12:31PM +0800, Maria Yu wrote:
>>>>>>>>>>>>>>>>>>>>>>> RPROC_OFFLINE state indicate there is no recovery process
>>>>>>>>>>>>>>>>>>>>>>> is in progress and no chance to do the pm_relax.
>>>>>>>>>>>>>>>>>>>>>>> Because when recovering from crash, rproc->lock is held and
>>>>>>>>>>>>>>>>>>>>>>> state is RPROC_CRASHED -> RPROC_OFFLINE -> RPROC_RUNNING,
>>>>>>>>>>>>>>>>>>>>>>> and then unlock rproc->lock.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> You are correct - because the lock is held rproc->state should be set to
>>>>>>>>>>>>>>>>>>>>>> RPROC_RUNNING
>>>>>>>>>>>>>>>>>>>>>> when rproc_trigger_recovery() returns. If that is not the case then
>>>>>>>>>>>>>>>>>>>>>> something
>>>>>>>>>>>>>>>>>>>>>> went wrong.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Function rproc_stop() sets rproc->state to RPROC_OFFLINE just before
>>>>>>>>>>>>>>>>>>>>>> returning,
>>>>>>>>>>>>>>>>>>>>>> so we know the remote processor was stopped. Therefore if rproc->state
>>>>>>>>>>>>>>>>>>>>>> is set
>>>>>>>>>>>>>>>>>>>>>> to RPROC_OFFLINE something went wrong in either request_firmware() or
>>>>>>>>>>>>>>>>>>>>>> rproc_start(). Either way the remote processor is offline and the system
>>>>>>>>>>>>>>>>>>>>>> probably
>>>>>>>>>>>>>>>>>>>>>> in an unknown/unstable. As such I don't see how calling pm_relax() can help
>>>>>>>>>>>>>>>>>>>>>> things along.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> PROC_OFFLINE is possible that rproc_shutdown is triggered and successfully
>>>>>>>>>>>>>>>>>>>>> finished.
>>>>>>>>>>>>>>>>>>>>> Even if it is multi crash rproc_crash_handler_work contention issue, and
>>>>>>>>>>>>>>>>>>>>> last rproc_trigger_recovery bailed out with only
>>>>>>>>>>>>>>>>>>>>> rproc->state==RPROC_OFFLINE, it is still worth to do pm_relax in pair.
>>>>>>>>>>>>>>>>>>>>> Since the subsystem may still can be recovered with customer's next trigger
>>>>>>>>>>>>>>>>>>>>> of rproc_start, and we can make each error out path clean with pm resources.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> I suggest spending time understanding what leads to the failure when
>>>>>>>>>>>>>>>>>>>>>> recovering
>>>>>>>>>>>>>>>>>>>>>> from a crash and address that problem(s).
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> In current case, the customer's information is that the issue happened when
>>>>>>>>>>>>>>>>>>>>> rproc_shutdown is triggered at similar time. So not an issue from error out
>>>>>>>>>>>>>>>>>>>>> of rproc_trigger_recovery.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> That is a very important element to consider and should have been mentioned
>>>>>>>>>>>>>>>>>>>> from
>>>>>>>>>>>>>>>>>>>> the beginning. What I see happening is the following:
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> rproc_report_crash()
>>>>>>>>>>>>>>>>>>>> pm_stay_awake()
>>>>>>>>>>>>>>>>>>>> queue_work() // current thread is suspended
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> rproc_shutdown()
>>>>>>>>>>>>>>>>>>>> rproc_stop()
>>>>>>>>>>>>>>>>>>>> rproc->state = RPROC_OFFLINE;
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> rproc_crash_handler_work()
>>>>>>>>>>>>>>>>>>>> if (rproc->state == RPROC_OFFLINE)
>>>>>>>>>>>>>>>>>>>> return // pm_relax() is not called
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> The right way to fix this is to add a pm_relax() in rproc_shutdown() and
>>>>>>>>>>>>>>>>>>>> rproc_detach(), along with a very descriptive comment as to why it is needed.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Thinking about this further there are more ramifications to consider. Please
>>>>>>>>>>>>>>>>>>> confirm the above scenario is what you are facing. I will advise on how to
>>>>>>>>>>>>>>>>>>> move
>>>>>>>>>>>>>>>>>>> forward if that is the case.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Not sure if the situation is clear or not. So resend the email again.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> The above senario is what customer is facing. crash hanppened while at
>>>>>>>>>>>>>>>>>> the same time shutdown is triggered.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Unfortunately this is not enough details to address a problem as
>>>>>>>>>>>>>>>>> complex as this one.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> And the device cannto goes to suspend state after that.
>>>>>>>>>>>>>>>>>> the subsystem can still be start normally after this.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> If the code flow I pasted above reflects the problem at hand, the
>>>>>>>>>>>>>>>>> current patch will not be sufficient to address the issue. If Arnaud
>>>>>>>>>>>>>>>>> confirms my suspicions we will have to think about a better solution.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Hi Mathiew,
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Could you pls have more details of any side effects other then power issue of
>>>>>>>>>>>>>>>> the current senario?
>>>>>>>>>>>>>>>> Why the current patch is not sufficient pls?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Have the current senario in details with rproc->lock information in details:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> | subsystem crashed interrupt issued | user trigger shutdown
>>>>>>>>>>>>>>>> | rproc_report_crash() |
>>>>>>>>>>>>>>>> | pm_stay_awake() |
>>>>>>>>>>>>>>>> | queue_work() |
>>>>>>>>>>>>>>>> | |rproc_shutdown
>>>>>>>>>>>>>>>> | |mutex_lock(&rproc->lock);
>>>>>>>>>>>>>>>> | |rproc_stop()
>>>>>>>>>>>>>>>> |rproc_crash_handler_work() |rproc->state = RPROC_OFFLINE;
>>>>>>>>>>>>>>>> | |mutex_unlock(&rproc->lock);
>>>>>>>>>>>>>>>> |mutex_lock(&rproc->lock); |
>>>>>>>>>>>>>>>> |if (rproc->state == RPROC_OFFLINE) |
>>>>>>>>>>>>>>>> |return // pm_relax() is not called |rproc_boot
>>>>>>>>>>>>>>>> |mutex_unlock(&rproc->lock); |
>>>>>>>>>>>>>>>> | |mutex_lock(&rproc->lock);
>>>>>>>>>>>>>>>> | |rproc_start()
>>>>>>>>>>>>>>>> | |mutex_unlock(&rproc->lock);
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Agree with Mathieu, this is not so simple.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks for looking into this.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Here is my view hoping I haven't missed a point in your discussion or
>>>>>>>>>>>>>>> an other corner cases.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I tried to analyze the issues (in what follows, the term "condition" means
>>>>>>>>>>>>>>> the "if" condition in which Aiqun proposes to add the fix) :
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I can see 4 use cases with race condition
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 1) crash report while already one is treated (rproc_boot_recovery called)
>>>>>>>>>>>>>>> => not a real use case as if the remote processor is crashed we
>>>>>>>>>>>>>>> should not have a second crash report
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> That part is of great concern to me. *Theoretically* we should not
>>>>>>>>>>>>>> get a new crash report while one has already been dispatched but the
>>>>>>>>>>>>>> current code accounts for this scenario and as such the possibility
>>>>>>>>>>>>>> can't be dismissed. Therefore we need to expect rproc_report_crash()
>>>>>>>>>>>>>> to be called multiple times before a single instance of
>>>>>>>>>>>>>> rproc_boot_recovery() is scheduled.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 2) rproc_stop executed between the queuing of the crash work and the call of
>>>>>>>>>>>>>>> rproc_crash_handler_work
>>>>>>>>>>>>>>> => rproc->state = RPROC_OFFLINE
>>>>>>>>>>>>>>> => we enter in the "condition" and the pm_relax has to be called
>>>>>>>>>>>>>>> => This commit fix should solve this use case
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 3) rproc_detach executed between the queue of the crash work and the call of
>>>>>>>>>>>>>>> rproc_crash_handler_work
>>>>>>>>>>>>>>> => rproc->state = RPROC_DETACHED;
>>>>>>>>>>>>>>> => we don't go in "the condition" and issue because the recovery reattach
>>>>>>>>>>>>>>> to the remote processor
>>>>>>>>>>>>>>> => but pm_relax is called
>>>>>>>>>>>>>>> => probably need an extra fix to avoid to re-attach
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 4) crash report while already one is treated (rproc_attach_recovery called)
>>>>>>>>>>>>>>> this one corresponds to an auto reboot of the remote processor, with a
>>>>>>>>>>>>>>> new crash
>>>>>>>>>>>>>>> => rproc->state = RPROC_CRASHED or rproc->state = RPROC_DETACHED;
>>>>>>>>>>>>>>> 4)a) rproc->state = RPROC_CRASHED if rproc->recovery_disabled = true
>>>>>>>>>>>>>>> => should call pm_relax if rproc->recovery_disabled = true
>>>>>>>>>>>>>>> => commit does not work for this use case
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 4)b) rproc->state = RPROC_DETACHED if recovery fails
>>>>>>>>>>>>>>> => error case with an unstable state
>>>>>>>>>>>>>>> => how to differentiate it from the use case 3) ?
>>>>>>>>>>>>>>> => introduce a RPROC_RECOVERY_FAIL state?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The case where a recovery fails needs to be considered and is the
>>>>>>>>>>>>>> reason the original patch doesn't work. Right now in
>>>>>>>>>>>>>> rproc_crash_handler_work(), it is not possible to differentiate
>>>>>>>>>>>>>> between a legitimate shutdown request (scenario #2 above) and a
>>>>>>>>>>>>>> recovery that went wrong. I think introducing RPROC_RECOVERY_FAIL
>>>>>>>>>>>>>> would greatly simplify things.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> My initial evaluation had not considered the attach/detach scenarios -
>>>>>>>>>>>>>> thanks for adding that in the mix.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Aiqun, please send a new patchset that adds a new remote processor
>>>>>>>>>>>>>> state, i.e RPROC_RECOVERY_FAIL. There should also be another patch in
>>>>>>>>>>>>>> that set that takes attach/detach scenarios into account. The code
>>>>>>>>>>>>>> between the v6.0 and v6.1 cycle has changed a lot in that area so make
>>>>>>>>>>>>>> sure to properly rebase.
>>>>>>>>>>>>>>
>>>>>>>>>>>>> I will try.
>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Then pm_stay_awake is called when the crash work is queued.
>>>>>>>>>>>>>>> It seems to me coherent to call the pm_relax in the work handler.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Here is a quick and dirty patch (not tested) that should take into account the
>>>>>>>>>>>>>>> main use cases ( except 1) and 4)b) )
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> @@ -2009,8 +2009,18 @@ static void rproc_crash_handler_work(struct work_struct *work)
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> mutex_lock(&rproc->lock);
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> - if (rproc->state == RPROC_CRASHED || rproc->state == RPROC_OFFLINE) {
>>>>>>>>>>>>>>> + if (rproc->state == RPROC_CRASHED || rproc->state == RPROC_OFFLINE ||
>>>>>>>>>>>>>>> + rproc->state == RPROC_DETACHED) {
>>>>>>>>>>>>>>> /* handle only the first crash detected */
>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>> + /*
>>>>>>>>>>>>>>> + * call pm-relax in following use cases:
>>>>>>>>>>>>>>> + * - the remote processor has been stopped by the user
>>>>>>>>>>>>>>> + * - the remote processor is detached
>>>>>>>>>>>>>>> + + - the remote proc has an autonomous reset but recovery_disabled is true.
>>>>>>>>>>>>>>> + */
>>>>>>>>>>>>>>> + if(rproc->state != RPROC_CRASHED || rproc->recovery_disabled)
>>>>>>>>>>>>>>> + pm_relax(rproc->dev.parent);
>>>>>>>>>>>>>>> mutex_unlock(&rproc->lock);
>>>>>>>>>>>>>>> return;
>>>>>>>>>>>>>>> }
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Regards,
>>>>>>>>>>>>>>> Arnaud
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>>>>> Mathieu
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> When the state is in RPROC_OFFLINE it means separate request
>>>>>>>>>>>>>>>>>>>>>>> of rproc_stop was done and no need to hold the wakeup source
>>>>>>>>>>>>>>>>>>>>>>> in crash handler to recover any more.
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> Signed-off-by: Maria Yu <quic_aiquny@...cinc.com>
>>>>>>>>>>>>>>>>>>>>>>> ---
>>>>>>>>>>>>>>>>>>>>>>> drivers/remoteproc/remoteproc_core.c | 11 +++++++++++
>>>>>>>>>>>>>>>>>>>>>>> 1 file changed, 11 insertions(+)
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> diff --git a/drivers/remoteproc/remoteproc_core.c
>>>>>>>>>>>>>>>>>>>>>>> b/drivers/remoteproc/remoteproc_core.c
>>>>>>>>>>>>>>>>>>>>>>> index e5279ed9a8d7..6bc7b8b7d01e 100644
>>>>>>>>>>>>>>>>>>>>>>> --- a/drivers/remoteproc/remoteproc_core.c
>>>>>>>>>>>>>>>>>>>>>>> +++ b/drivers/remoteproc/remoteproc_core.c
>>>>>>>>>>>>>>>>>>>>>>> @@ -1956,6 +1956,17 @@ static void rproc_crash_handler_work(struct
>>>>>>>>>>>>>>>>>>>>>>> work_struct *work)
>>>>>>>>>>>>>>>>>>>>>>> if (rproc->state == RPROC_CRASHED || rproc->state ==
>>>>>>>>>>>>>>>>>>>>>>> RPROC_OFFLINE) {
>>>>>>>>>>>>>>>>>>>>>>> /* handle only the first crash detected */
>>>>>>>>>>>>>>>>>>>>>>> mutex_unlock(&rproc->lock);
>>>>>>>>>>>>>>>>>>>>>>> + /*
>>>>>>>>>>>>>>>>>>>>>>> + * RPROC_OFFLINE state indicate there is no recovery process
>>>>>>>>>>>>>>>>>>>>>>> + * is in progress and no chance to have pm_relax in place.
>>>>>>>>>>>>>>>>>>>>>>> + * Because when recovering from crash, rproc->lock is held and
>>>>>>>>>>>>>>>>>>>>>>> + * state is RPROC_CRASHED -> RPROC_OFFLINE -> RPROC_RUNNING,
>>>>>>>>>>>>>>>>>>>>>>> + * and then unlock rproc->lock.
>>>>>>>>>>>>>>>>>>>>>>> + * RPROC_OFFLINE is only an intermediate state in recovery
>>>>>>>>>>>>>>>>>>>>>>> + * process.
>>>>>>>>>>>>>>>>>>>>>>> + */
>>>>>>>>>>>>>>>>>>>>>>> + if (rproc->state == RPROC_OFFLINE)
>>>>>>>>>>>>>>>>>>>>>>> + pm_relax(rproc->dev.parent);
>>>>>>>>>>>>>>>>>>>>>>> return;
>>>>>>>>>>>>>>>>>>>>>>> }
>>>>>>>>>>>>>>>>>>>>>>> --
>>>>>>>>>>>>>>>>>>>>>>> 2.7.4
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> --
>>>>>>>>>>>>>>>>>>>>> Thx and BRs,
>>>>>>>>>>>>>>>>>>>>> Aiqun(Maria) Yu
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> --
>>>>>>>>>>>>>>>>>> Thx and BRs,
>>>>>>>>>>>>>>>>>> Aiqun(Maria) Yu
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> --
>>>>>>>>>>>>> Thx and BRs,
>>>>>>>>>>>>> Aiqun(Maria) Yu
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> --
>>>>>>>>>>> Thx and BRs,
>>>>>>>>>>> Aiqun(Maria) Yu
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> Thx and BRs,
>>>>>>>>> Aiqun(Maria) Yu
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Thx and BRs,
>>>>>>> Aiqun(Maria) Yu
>>>>>
>>>>>
>>>>> --
>>>>> Thx and BRs,
>>>>> Aiqun(Maria) Yu
>>
>>
>> --
>> Thx and BRs,
>> Aiqun(Maria) Yu
--
Thx and BRs,
Aiqun(Maria) Yu
Powered by blists - more mailing lists