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From: Jens Axboe <axboe@kernel.dk>
To: Thomas Gleixner <tglx@linutronix.de>, Oleg Nesterov <oleg@redhat.com>
Cc: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org,
	peterz@infradead.org, Roman Gershman <romger@amazon.com>
Subject: Re: [PATCH 5/5] task_work: use TIF_NOTIFY_SIGNAL if available
Date: Fri, 16 Oct 2020 12:05:50 -0600	[thread overview]
Message-ID: <ce2160c6-666b-0231-3c8d-499958ef733d@kernel.dk> (raw)
In-Reply-To: <874kmuaw13.fsf@nanos.tec.linutronix.de>

On 10/16/20 12:03 PM, Thomas Gleixner wrote:
> On Fri, Oct 16 2020 at 08:53, Jens Axboe wrote:
>> On 10/16/20 8:51 AM, Oleg Nesterov wrote:
>>> On 10/16, Thomas Gleixner wrote:
>>>>
>>>> With moving the handling into get_signal() you don't need more changes
>>>> to arch/* than adding the TIF bit, right?
>>>
>>> we still need to do something like
>>>
>>> 	-	if (thread_flags & _TIF_SIGPENDING)
>>> 	+	if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
>>> 			do_signal(...);
>>>
>>> and add _TIF_NOTIFY_SIGNAL to the WORK-PENDING mask in arch/* code.
>>
>> Yes, but it becomes really minimal at that point, and just that. There's
>> no touching any of the arch do_signal() code.
>>
>> Just finished the update of the branch to this model, and it does simplify
>> things quite a bit! Most arch patches are now exactly just what you write
>> above, no more.
> 
> Except for all the nasty ones which have these checks in ASM :)

Actually not that many of them, and the biggest part of that set are
easy enough too (just adding the mask to the check). The only exceptions
are where TIF_NOTIFY_SIGNAL end up spilling over 8/16-bit, and the
particular arch currently uses some mask compare variant that now needs
to be modified. powerpc was the worst there, but I'm told a free bit
will show up in the merge window so all my powerpc asm fiddling was for
naught :-)

Only remaining issue I'm aware of in the arch conversions is arm, which
runs into this exact issue. Need to check with some arm guys on what the
best approach is there...

-- 
Jens Axboe


  reply	other threads:[~2020-10-16 18:05 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-15 13:16 [PATCHSET v5] Add support for TIF_NOTIFY_SIGNAL Jens Axboe
2020-10-15 13:16 ` [PATCH 1/5] tracehook: clear TIF_NOTIFY_RESUME in tracehook_notify_resume() Jens Axboe
2020-10-15 14:42   ` Oleg Nesterov
2020-10-15 14:43     ` Jens Axboe
2020-10-15 13:16 ` [PATCH 2/5] kernel: add task_sigpending() helper Jens Axboe
2020-10-15 14:42   ` Oleg Nesterov
2020-10-15 13:16 ` [PATCH 3/5] kernel: add support for TIF_NOTIFY_SIGNAL Jens Axboe
2020-10-15 14:31   ` Oleg Nesterov
2020-10-15 14:33     ` Jens Axboe
2020-10-15 14:37       ` Oleg Nesterov
2020-10-15 14:43         ` Jens Axboe
2020-10-15 14:47           ` Oleg Nesterov
2020-10-15 14:53             ` Oleg Nesterov
2020-10-15 14:56               ` Jens Axboe
2020-10-15 15:01         ` Thomas Gleixner
2020-10-15 15:27           ` Oleg Nesterov
2020-10-15 14:44   ` Oleg Nesterov
2020-10-15 13:17 ` [PATCH 4/5] x86: wire up TIF_NOTIFY_SIGNAL Jens Axboe
2020-10-15 14:11   ` Thomas Gleixner
2020-10-15 14:31     ` Jens Axboe
2020-10-15 14:34       ` Thomas Gleixner
2020-10-15 14:35         ` Jens Axboe
2020-10-15 14:36       ` Oleg Nesterov
2020-10-15 14:42         ` Jens Axboe
2020-10-15 14:34     ` Oleg Nesterov
2020-10-15 14:54       ` Thomas Gleixner
2020-10-15 15:17         ` Oleg Nesterov
2020-10-16  9:55       ` Thomas Gleixner
2020-10-16 10:54         ` Oleg Nesterov
2020-10-16 13:07           ` Thomas Gleixner
2020-10-15 14:44   ` Oleg Nesterov
2020-10-20 10:57   ` introduce asm-generic/thread_info.h ? Oleg Nesterov
2020-10-15 13:17 ` [PATCH 5/5] task_work: use TIF_NOTIFY_SIGNAL if available Jens Axboe
2020-10-15 15:49   ` Oleg Nesterov
2020-10-15 18:39     ` Jens Axboe
2020-10-16  9:00       ` Thomas Gleixner
2020-10-16  9:39         ` Thomas Gleixner
2020-10-16 13:35           ` Jens Axboe
2020-10-16 14:17             ` Thomas Gleixner
2020-10-16 14:51               ` Oleg Nesterov
2020-10-16 14:53                 ` Jens Axboe
2020-10-16 18:03                   ` Thomas Gleixner
2020-10-16 18:05                     ` Jens Axboe [this message]
2020-10-16 13:33         ` Jens Axboe
2020-10-16 14:11           ` Thomas Gleixner
2020-10-16 14:22             ` Jens Axboe

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