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

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Message-ID: <de00f13d-9ff0-6955-5d37-557f044ce2aa@kernel.dk>
Date:   Thu, 8 Oct 2020 08:31:32 -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 8:21 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.

-- 
Jens Axboe