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AJvYcCVL50vOqj+Pfg7eov1j02/L+6gt8/uRKSlOpmEhqMhlr1tRrgmxuaY+12SAFa3o66CnPnDUQ3RjoA==@kvack.org X-Gm-Message-State: AOJu0YzXoEEF+H0s8WNqz/9zz+0bQuv8EziC4Nd/UNfnxdwtEsrj+jLf 4Agp5fm/w/VCigUbcBU5jlqid82yW6IcC5PTQW0W8pb26et8pkY/Nc8Kbd21We9bqXTGkYSbQpA rTXYYJzvL7QohFvSqYebdZOwwabb6ZJ8= X-Gm-Gg: ASbGncvSVtoNbEJwwnRcuV+Az56j6VGhJv1nOfy1XtBNoe7DEgFpHQRQ0dGweK6OAca iEUjKEVORHs3/9/afgSwP6BGC+iWboO5bguwow7gDDwrOJ8IGwWSYp/K4cMZoLq3tSn3ZjLcqwo 1Vst461tqXg/eF7i8cc4lLZK1u+4zmZonoGCX+0gZp3M386S/1XZ1hKyoGjr1TiAmX70JuH6lFM Fikt4T6SItNPmGvVdfYN5FfCPFgM8vPek2l9cQJiw== X-Google-Smtp-Source: AGHT+IFY8gu/RrCyr3edgcmpVM4R2w44fG9KMd2O0YJMqKVLqnlWjuRIpRapn1ch7o9iKR+T1hVRKcHiM4nMmDW1D0I= X-Received: by 2002:a2e:a54a:0:b0:336:89dd:41ba with SMTP id 38308e7fff4ca-33689dd43ebmr8627441fa.9.1756225412701; Tue, 26 Aug 2025 09:23:32 -0700 (PDT) MIME-Version: 1.0 References: <20250730142301.6754-1-pranav.tyagi03@gmail.com> In-Reply-To: From: Pranav Tyagi Date: Tue, 26 Aug 2025 21:53:20 +0530 X-Gm-Features: Ac12FXxDQE7gyOdZYAnPp3w1u4iY3ylCUDIqHFUVWVKzr1Z2KPlM4NdLcQSO8Lw Message-ID: Subject: Re: [PATCH] selftests/mm: use __auto_type in swap() macro To: Peter Xu Cc: akpm@linux-foundation.org, shuah@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: EA019140012 X-Stat-Signature: xydno3mcxnfisrkautaome19tg7ntyqn X-HE-Tag: 1756225414-588697 X-HE-Meta: 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 Lmc4JomW BkRhPzztKGvQkfmAgxqhrtBU82G08d567cQGOCPQHbe4Ie7/ptRCJlPZaJnEoZsIBDbv8LHzUzutfu1TEFpFh/262uLudLu5L14KfOkakUtZ7Zni2LV6WguMmwtrbT2U8SsyDX+/iozdmfwIkqcJ387ZOZVv146zEPjCfBf6fTLD+Id35ctjMKQxWHLYqG0QX7asCG7DhDiPURmLKxXrAgxq3zvIiVdSR7nfTyytFD+4fYFaWa/D3pTYS9HgdG70N4FhomiJEP/sYxOg+8cxkmF0Y6AmxIBrROsxd8RgHz4TBZgxehVBxI9h5pQXJA9ihLvmjNI6PMq/0lqqDHP+qIgjMSWoCgE4Kla+9v0Ygw64bzHkSZF3GSN+dl/QswaIIAmzAuF5N0Zx8pvrc4LkyaEyNvpAXgGhD/LKkgPQ3JJHX8BlPdc+ThKAWqx5GnkKtoLHehfwTY+LiOzEsPrWyWSYvTHjRJPEJYU8H X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Wed, Aug 6, 2025 at 10:16=E2=80=AFPM Peter Xu wrote: > > On Wed, Aug 06, 2025 at 09:15:50PM +0530, Pranav Tyagi wrote: > > On Wed, Jul 30, 2025 at 7:53=E2=80=AFPM Pranav Tyagi wrote: > > > > > > Replace typeof() with __auto_type in the swap() macro in uffd-stress.= c. > > > __auto_type was introduced in GCC 4.9 and reduces the compile time fo= r > > > all compilers. No functional changes intended. > > > > > > Signed-off-by: Pranav Tyagi > > > --- > > > tools/testing/selftests/mm/uffd-stress.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing= /selftests/mm/uffd-stress.c > > > index 40af7f67c407..c0f64df5085c 100644 > > > --- a/tools/testing/selftests/mm/uffd-stress.c > > > +++ b/tools/testing/selftests/mm/uffd-stress.c > > > @@ -51,7 +51,7 @@ static char *zeropage; > > > pthread_attr_t attr; > > > > > > #define swap(a, b) \ > > > - do { typeof(a) __tmp =3D (a); (a) =3D (b); (b) =3D __tmp; } w= hile (0) > > > + do { __auto_type __tmp =3D (a); (a) =3D (b); (b) =3D __tmp; }= while (0) > > > > > > const char *examples =3D > > > "# Run anonymous memory test on 100MiB region with 99999 boun= ces:\n" > > > -- > > > 2.49.0 > > > > > > > Hi, > > > > Just a gentle follow-up on this cleanup patch. From what I could find, > > this is the only use of > > typeof() left in the mm selftests, so this should be the only instance > > needing this change. > > > > Thanks for considering! > > Hi, > > Andrew should have queued this one in branch akpm/mm-nonmm-unstable (even > though I'm not familiar with the branch). > > Said that, I'm also not familiar with __auto_type. Looks like it's more > efficiently processed by the compiler in some special use cases, however > it's also new so maybe some tools (sparse?) may not recognize it. > > Is it the plan that the whole Linux kernel is moving towards __auto_type? > I still see quite a few of typeof() usages (not "a few", but 2966 instanc= es). > > Thanks, > > -- > Peter Xu > Hi Peter, Thank you for the feedback and I sincerely apologize for the delayed response. You=E2=80=99re right =E2=80=94 this patch was initially queued under akpm/m= m-nonmm-unstable and it now lives in the mm-unstable branch. The motivation behind switching to __auto_type is twofold: it reduces compi= le time across compilers and improves readability. Support for __auto_type has been available in GCC since 4.9 (quite some time back) and in sparse since v0.6.2 (2020). To the best of my knowledge, it has since been widely adopte= d by toolchains. That said, I acknowledge there are still many uses of typeof() in the kerne= l, as you pointed out. My intent with this patch (and a few related ones I=E2= =80=99ve submitted) is to encourage more consistent use of __auto_type, starting wit= h selftests where it is already in use in several places. Thanks again for your review and for pointing out the current branch status= . Regards Pranav Tyagi