linux-kernel - Re: [PATCH 3/6] kernel: split syscall restart from signal handling

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Message-ID: <0c06829a-17dc-3adc-f96a-25b2a41ea00c@kernel.dk>
Date:   Thu, 8 Oct 2020 08:41:13 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        peterz@...radead.org, tglx@...utronix.de
Subject: Re: [PATCH 3/6] kernel: split syscall restart from signal handling

On 10/8/20 8:31 AM, Jens Axboe wrote:
> On 10/8/20 8:21 AM, Oleg Nesterov wrote:
>> On 10/05, Jens Axboe wrote:
>>>
>>> Move the restart syscall logic into a separate generic entry helper,
>>> and handle that part separately from signal checking and delivery.
>>>
>>> This is in preparation for being able to do syscall restarting
>>> independently from handling signals.
>>>
>>> Signed-off-by: Jens Axboe <axboe@...nel.dk>
>>> ---
>>>  arch/x86/kernel/signal.c     | 32 ++++++++++++++++++--------------
>>>  include/linux/entry-common.h | 14 ++++++++++++--
>>>  kernel/entry/common.c        | 11 ++++++++---
>>>  3 files changed, 38 insertions(+), 19 deletions(-)
>>
>> Can't we avoid this patch and the and simplify the change in
>> exit_to_user_mode_loop() from the next patch? Can't the much more simple
>> patch below work?
>>
>> Then later we can even change arch_do_signal() to accept the additional
>> argument, ti_work, so that it can use ti_work & TIF_NOTIFY_SIGNAL/SIGPENDING
>> instead of test_thread_flag/task_sigpending.
> 
> Yeah I guess that would be a bit simpler, maybe I'm too focused on
> decoupling the two. But if we go this route, and avoid sighand->lock for
> just having TIF_NOTIFY_SIGNAL set, then that should be functionally
> equivalent as far as I'm concerned.
> 
> I'll make the reduction, I'd prefer to keep this as small/simple as
> possible initially.

FWIW, then we should also just integrate the x86 define change into
that patch, so we can drop patches 3 + 5 with this change.

-- 
Jens Axboe