Re: [PATCH v10 4/4] cgroups: implement the PIDs subsystem

From: Aleksa Sarai <cyphar@cyphar.com>
To: Tejun Heo <tj@kernel.org>
Cc: lizefan@huawei.com, mingo@redhat.com,
	"Peter Zijlstra" <peterz@infradead.org>,
	richard@nod.at, "Frédéric Weisbecker" <fweisbec@gmail.com>,
	linux-kernel@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [PATCH v10 4/4] cgroups: implement the PIDs subsystem
Date: Thu, 14 May 2015 03:04:52 +1000	[thread overview]
Message-ID: <CAOviyah9yyXJG0eUeizpb5ZnzNUAKfxXGkXJw-5sNw7sQOAEuA@mail.gmail.com> (raw)
In-Reply-To: <20150424153657.GC24029@htj.duckdns.org>

Hi Tejun

>> >> +     /* We use INT_MAX as the maximum value of pid_t. */
>> >> +     if (limit < 0 || limit > INT_MAX)
>> >
>> > This is kinda weird if we're using PIDS_MAX for max as it may end up
>> > showing "max" after some larger number is written to the file.
>>
>> The reason for this is because I believe you said "PIDS_MAX isn't
>> meant to be exposed to userspace" (one of the previous patchsets used
>> PIDS_MAX as the maximum valid value).
>
> Yeah, but wouldn't it be weird to allow the userland to input PIDS_MAX
> (whatever value that may be) and reads back max?  It can be whatever
> maximum input value + 1, no?

Would you be okay with this?

    if (limit < 0 || limit >= PIDS_MAX)

I'd prefer if we used PIDS_MAX as the maximum input value as well as
being the internal representation of the maximum, rather than
switching to something like INT_MAX.

--
Aleksa Sarai (cyphar)
www.cyphar.com