From: Xiaofei Tan <tanxiaofei@huawei.com>
To: James Morse <james.morse@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Linuxarm <linuxarm@huawei.com>, Will Deacon <will@kernel.org>,
Dave Martin <Dave.Martin@arm.com>,
linux-arm-kernel@lists.infradead.org,
Shiju Jose <shiju.jose@huawei.com>
Subject: Re: Question about SEA handling process happened in user space
Date: Sat, 18 Apr 2020 19:25:29 +0800 [thread overview]
Message-ID: <5E9AE3A9.5020904@huawei.com> (raw)
In-Reply-To: <bddb100a-7353-1aac-9877-9c5df5bd2c92@arm.com>
Hi James
On 2020/4/16 21:50, James Morse wrote:
> On 10/04/2020 10:43, Xiaofei Tan wrote:
>> On 2020/4/9 22:28, James Morse wrote:
>>> On 09/04/2020 10:17, Xiaofei Tan wrote:
>>>> On 2020/4/8 0:37, James Morse wrote:
>>>>> With that series, it runs in process-context as task-work. memory_failure() needs to
>>>>> sleep, so it has to run in process-context.
>
>>>>> Doing it as task-work means it runs before the thread returns to user-space.
>>>>
>>>> Sorry, i don't understand this. i thought the task-work need to reschedule, and current thread should
>>>> have returned to user-space before it.
>>>
>>> ret_to_user has a loop around do_notify_resume(), if the _TIF_NOTIFY_RESUME flag is set
>>> and we call tracehook_notify_resume() which ends up in task_work_run()...
>>>
>>> That TIF flag effectively prevents this thread returning to user-space until that task
>>> work has run.
>
>> Got it. This function is great.
>
> I think PeterZ pointed me at it,
>
Great.
>
>> BTW, i have not found the place of setting the flag _TIF_NOTIFY_RESUME. Is it set by default for each thread?
>
> With that series, APEI calls task_work_add(), which calls set_notify_resume() from
> include/linux/tracehook.h
> | if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
>
Got it. thanks.
>
> Thanks,
>
> James
>
> .
>
--
thanks
tanxiaofei
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prev parent reply other threads:[~2020-04-18 11:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 13:10 Question about SEA handling process happened in user space Xiaofei Tan
2020-03-30 16:49 ` James Morse
2020-03-31 9:41 ` Xiaofei Tan
2020-03-31 17:00 ` James Morse
2020-04-01 3:49 ` Xiaofei Tan
2020-04-07 16:37 ` James Morse
2020-04-09 8:42 ` Xiaofei Tan
2020-04-09 14:28 ` James Morse
2020-04-10 2:55 ` Xiaofei Tan
2020-04-16 13:27 ` James Morse
2020-04-18 10:49 ` Xiaofei Tan
2020-04-02 6:35 ` Xiaofei Tan
2020-04-07 16:37 ` James Morse
2020-04-09 9:17 ` Xiaofei Tan
2020-04-09 14:28 ` James Morse
2020-04-10 9:43 ` Xiaofei Tan
2020-04-16 13:50 ` James Morse
2020-04-18 11:25 ` Xiaofei Tan [this message]
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