lkml.org 
[lkml]   [2021]   [May]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 1/1] remoteproc: use freezable workqueue for crash notifications
From
Date

On 5/27/2021 8:55 PM, Bjorn Andersson wrote:
> On Wed 19 May 18:44 CDT 2021, Alex Elder wrote:
>
>> When a remoteproc has crashed, rproc_report_crash() is called to
>> handle whatever recovery is desired. This can happen at almost any
>> time, often triggered by an interrupt, though it can also be
>> initiated by a write to debugfs file remoteproc/remoteproc*/crash.
>>
>> When a crash is reported, the crash handler worker is scheduled to
>> run (rproc_crash_handler_work()). One thing that worker does is
>> call rproc_trigger_recovery(), which calls rproc_stop(). That calls
>> the ->stop method for any remoteproc subdevices before making the
>> remote processor go offline.
>>
>> The Q6V5 modem remoteproc driver implements an SSR subdevice that
>> notifies registered drivers when the modem changes operational state
>> (prepare, started, stop/crash, unprepared). The IPA driver
>> registers to receive these notifications.
>>
>> With that as context, I'll now describe the problem.
>>
>> There was a situation in which buggy modem firmware led to a modem
>> crash very soon after system (AP) resume had begun. The crash caused
>> a remoteproc SSR crash notification to be sent to the IPA driver.
>> The problem was that, although system resume had begun, it had not
>> yet completed, and the IPA driver was still in a suspended state.
>>
>> This scenario could happen to any driver that registers for these
>> SSR notifications, because they are delivered without knowledge of
>> the (suspend) state of registered recipient drivers.
>>
>> This patch offers a simple fix for this, by having the crash
>> handling worker function run on the system freezable workqueue.
>> This workqueue does not operate if user space is frozen (for
>> suspend). As a result, the SSR subdevice only delivers its
>> crash notification when the system is fully operational (i.e.,
>> neither suspended nor in suspend/resume transition).
>>
> This makes sense to me; both that it ensures that we spend our resources
> on the actual system resume and that it avoids surprises from this
> happening while the system still is in a funky state...
>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
>
> But it would be nice to get some input from other users of the
> framework.
This patch sounds like a good idea for cases where the
request_firmware() APIs fallback to userspace firmware loading.

Will test out this patch and report back.

Thanks,
Sid
>
> Regards,
> Bjorn
>
>> Signed-off-by: Alex Elder <elder@linaro.org>
>> ---
>> drivers/remoteproc/remoteproc_core.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>> index 39cf44cb08035..6bedf2d2af239 100644
>> --- a/drivers/remoteproc/remoteproc_core.c
>> +++ b/drivers/remoteproc/remoteproc_core.c
>> @@ -2724,8 +2724,8 @@ void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type)
>> dev_err(&rproc->dev, "crash detected in %s: type %s\n",
>> rproc->name, rproc_crash_to_string(type));
>>
>> - /* create a new task to handle the error */
>> - schedule_work(&rproc->crash_handler);
>> + /* Have a worker handle the error; ensure system is not suspended */
>> + queue_work(system_freezable_wq, &rproc->crash_handler);
>> }
>> EXPORT_SYMBOL(rproc_report_crash);
>>
>> --
>> 2.27.0
>>

\
 
 \ /
  Last update: 2021-05-29 02:12    [W:0.124 / U:0.452 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site