Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Message-ID: <b4a669191a5a5d1bc9e900991a1b34c9d245e36f.camel@trillion01.com>
Subject: Re: [PATCH] io_thread/x86: don't reset 'cs', 'ss', 'ds' and 'es'
 registers for io_threads
From:   Olivier Langlois <olivier@trillion01.com>
To:     Jens Axboe <axboe@kernel.dk>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Stefan Metzmacher <metze@samba.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        io-uring <io-uring@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>
Date:   Tue, 25 May 2021 15:45:11 -0400
In-Reply-To: <d9a12052074ba194fe0764c932603a5f85c5445a.camel@trillion01.com>
References: <8735v3ex3h.ffs@nanos.tec.linutronix.de>
         <3C41339D-29A2-4AB1-958F-19DB0A92D8D7@amacapital.net>
         <CAHk-=wh0KoEZXPYMGkfkeVEerSCEF1AiCZSvz9TRrx=Kj74D+Q@mail.gmail.com>
         <CALCETrV9bCenqzzaW6Ra18tCvNP-my09decTjmLDVZZAQxR6VA@mail.gmail.com>
         <CAHk-=wgo6XEz3VQ9ntqzWLR3-hm1YXrXUz4_heDs4wcLe9NYvA@mail.gmail.com>
         <d26e3a82-8a2c-7354-d36b-cac945c208c7@kernel.dk>
         <CALCETrWmhquicE2C=G2Hmwfj4VNypXVxY-K3CWOkyMe9Edv88A@mail.gmail.com>
         <CAHk-=wgqK0qUskrzeWXmChErEm32UiOaUmynWdyrjAwNzkDKaw@mail.gmail.com>
         <8735v3jujv.ffs@nanos.tec.linutronix.de>
         <CAHk-=wi4Dyg_Z70J_hJbtFLPQDG+Zx3dP2jB5QrOdZC6W6j4Gw@mail.gmail.com>
         <12710fda-1732-ee55-9ac1-0df9882aa71b@samba.org>
         <CAHk-=wiR7c-UHh_3Rj-EU8=AbURKchnMFJWW7=5EH=qEUDT8wg@mail.gmail.com>
         <59ea3b5a-d7b3-b62e-cc83-1f32a83c4ac2@kernel.dk>
         <17471c9fec18765449ef3a5a4cddc23561b97f52.camel@trillion01.com>
         <CAHk-=whoJCocFsQ7+Sqq=dkuzHE+RXxvRdd4ZvyYqnsKBqsKAA@mail.gmail.com>
         <3df541c3-728c-c63d-eaeb-a4c382e01f0b@kernel.dk>
         <b360ed542526da0a510988ce30545f429a7da000.camel@trillion01.com>
         <4390e9fb839ebc0581083fc4fa7a82606432c0c0.camel@trillion01.com>
         <d9a12052074ba194fe0764c932603a5f85c5445a.camel@trillion01.com>
Organization: Trillion01 Inc
Content-Type: text/plain; charset="ISO-8859-1"
User-Agent: Evolution 3.40.1 
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

On Tue, 2021-05-25 at 15:39 -0400, Olivier Langlois wrote:
> This notion appears to be central when creating a coredump...
> Only tasks having the same mm than the one receiving the SIGSEGV will
> be zapped...
> 
> in zap_threads():
> ????????????????for_each_thread(g, p) {
> ????????????????????????if (unlikely(!p->mm))
> ????????????????????????????????continue;
> ????????????????????????if (unlikely(p->mm == mm)) {
> ????????????????????????????????lock_task_sighand(p, &flags);
> ????????????????????????????????nr += zap_process(p, exit_code,
> ????????????????????????????????????????????????????????SIGNAL_GROUP_
> E
> XIT);
> ????????????????????????????????unlock_task_sighand(p, &flags);
> ????????????????????????}
> ????????????????????????break;
> ????????????????}

without fully understanding what I am doing... I am tempted to tweak
the condition

(unlikely(p->mm == mm))

for

(unlikely(p->mm == mm || p->flags & PF_IO_WORKER))

and see if it would resolve my coredump problem...