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Subject: Re: [PATCH 2/8] kernel: unmask SIGSTOP for IO threads
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     io-uring@vger.kernel.org, torvalds@linux-foundation.org,
        ebiederm@xmission.com, metze@samba.org,
        linux-kernel@vger.kernel.org
References: <20210326003928.978750-1-axboe@kernel.dk>
 <20210326003928.978750-3-axboe@kernel.dk> <20210326134840.GA1290@redhat.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <a179ad33-5656-b644-0d92-e74a6bd26cc8@kernel.dk>
Date:   Fri, 26 Mar 2021 09:01:00 -0600
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On 3/26/21 7:48 AM, Oleg Nesterov wrote:
> Jens, sorry, I got lost :/

Let's bring you back in :-)

> On 03/25, Jens Axboe wrote:
>>
>> With IO threads accepting signals, including SIGSTOP,
> 
> where can I find this change? Looks like I wasn't cc'ed...

It's this very series.

>> unmask the
>> SIGSTOP signal from the default blocked mask.
>>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> ---
>>  kernel/fork.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/fork.c b/kernel/fork.c
>> index d3171e8e88e5..d5a40552910f 100644
>> --- a/kernel/fork.c
>> +++ b/kernel/fork.c
>> @@ -2435,7 +2435,7 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
>>  	tsk = copy_process(NULL, 0, node, &args);
>>  	if (!IS_ERR(tsk)) {
>>  		sigfillset(&tsk->blocked);
>> -		sigdelsetmask(&tsk->blocked, sigmask(SIGKILL));
>> +		sigdelsetmask(&tsk->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
> 
> siginitsetinv(blocked, sigmask(SIGKILL)|sigmask(SIGSTOP)) but this is minor.

Ah thanks.

> To remind, either way this is racy and can't really help.
> 
> And if "IO threads accepting signals" then I don't understand why. Sorry,
> I must have missed something.

I do think the above is a no-op at this point, and we can probably just
kill it. Let me double check, hopefully we can just remove this blocked
part.

-- 
Jens Axboe