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AJvYcCWFQPh+5aGAL5TZmfavPV34JgZvveYa4MFcrh3AcdrijZ1gxaQnQXar526aJ7sNuaUd7nCQn0gOiw==@kvack.org X-Gm-Message-State: AOJu0YwfPE6r1Ig/Or0JwoemBUDBe+1d361yyZnh3BIXPaIcuMpP3DLF OGV5awfCLOrogdJ6c0PSaBTgnxUTBFKCHX9lIzKbaKqMWMWXZ7I+L4U3hvyampSRGngFoXE4FPr 0EWMc8hKebYZ87CqYLfx1gkydeas= X-Google-Smtp-Source: AGHT+IEVUq57VuR5XJDhYVOCvnCwTfmEHGvoTOOB+teIWs3F3TJQh8yeiHRLwccdv5kTX5+vj5zTsLfWMZ4F/nufsZs= X-Received: by 2002:a05:6102:32ca:b0:4a4:7609:35f with SMTP id ada2fe7eead31-4a8cfd6d7bemr401289137.24.1729881550725; Fri, 25 Oct 2024 11:39:10 -0700 (PDT) MIME-Version: 1.0 References: <788fdfcc9ef602b408951d68097918d6ae379395.1729848252.git.lorenzo.stoakes@oracle.com> <828674d9-e862-4438-86b6-61977f4cf3b5@nvidia.com> In-Reply-To: <828674d9-e862-4438-86b6-61977f4cf3b5@nvidia.com> From: Pedro Falcato Date: Fri, 25 Oct 2024 19:38:59 +0100 Message-ID: Subject: Re: [PATCH v5 2/5] pidfd: add PIDFD_SELF_* sentinels to refer to own thread/process To: John Hubbard Cc: Lorenzo Stoakes , Christian Brauner , Shuah Khan , "Liam R . Howlett" , Suren Baghdasaryan , Vlastimil Babka , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Oliver Sang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: tswy97zgb1eowenzxqe4xa9d6tfx761h X-Rspamd-Queue-Id: AA0D480002 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1729881513-805513 X-HE-Meta: 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 omRbTd6o 0IL4teEKXi3Jeo6Lc2bpxcr7dDv0nxIV3OaI9SvKPgix4iTDhs+ls7ODLW5pDOZvo9WGuGwPjTTKB7NScQHufUAqX2xEzOPM2v1S8fT8s/mipXTd/ZzH98K+Jf2gvBHMm/OrzCUlgohHGgVWVKj4nbVkoBTuRqMUzvjVF+luOETuIRhYTtVdF6APLU//dqLwbxrzwBPEfuTpOoI2tkBitsTUMde1GIcsveLCzRsE9rdRoZ7XlebbilqgfaOrz1IuRD7TM6FgM12pNtDrTqKoAHoX/U9vAmUs641/dw67JshbOKZV5XQsmLn4qeld3IVUKWQYA2l1FBMI77nA0BBWt3TbrHdxbmn9yExLpTH7gua03Q0ZcSedxBhVY2+1ut/5bD8/tMe7G5BzOmzbC+RvLzQXkKafiKVgotU8+fB/v2KzjGum3IuSW3UNLtay7jwEolRQf X-Bogosity: Ham, tests=bogofilter, spamicity=0.000030, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 25, 2024 at 6:41=E2=80=AFPM John Hubbard = wrote: > > On 10/25/24 5:50 AM, Pedro Falcato wrote: > > On Fri, Oct 25, 2024 at 10:41=E2=80=AFAM Lorenzo Stoakes > > wrote: > ... > >> +static inline int pidfd_is_self_sentinel(pid_t pid) > >> +{ > >> + return pid =3D=3D PIDFD_SELF_THREAD || pid =3D=3D PIDFD_SELF_T= HREAD_GROUP; > >> +} > > > > Do we want this in the uapi header? Even if this is useful, it might > > come with several drawbacks such as breaking scripts that parse kernel > > headers (and a quick git grep suggests we do have static inlines in > > headers, but in rather obscure ones) and breaking C89: > > > > Let's please not say "C89" anymore, we've moved on! :) > > The notes in [1], which is now nearly 2.5 years old, discuss the move to > C11, and specifically how to handle the inline keyword. That seems to only apply to the kernel internally, uapi headers are included from userspace too (-std=3Dc89 -pedantic doesn't know what a gnu extension is). And uapi headers _generally_ keep to defining constants and structs, nothing more. I don't know what the guidelines for uapi headers are nowadays, but we generally want to not break userspace. > > I think it's quite clear at this point, that we should not hold up new > work, based on concerns about handling the inline keyword, nor about > C89. Right, but the correct solution is probably to move pidfd_is_self_sentinel to some other place, since it's not even supposed to be used by userspace (it's semantically useless to userspace, and it's only two users are in the kernel, kernel/pid.c and exit.c). --=20 Pedro