linux-kernel - Re: [PATCH v3 54/68] selftests/rseq: Drop define _GNU

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Date: Thu, 9 May 2024 16:16:20 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Edward Liaw <edliaw@...gle.com>, shuah@...nel.org,
 Mickaël Salaün <mic@...ikod.net>,
 Günther Noack <gnoack@...gle.com>,
 Christian Brauner <brauner@...nel.org>,
 Richard Cochran <richardcochran@...il.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Peter Zijlstra <peterz@...radead.org>, "Paul E. McKenney"
 <paulmck@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
 Muhammad Usama Anjum <usama.anjum@...labora.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 kernel-team@...roid.com, linux-security-module@...r.kernel.org,
 netdev@...r.kernel.org, linux-riscv@...ts.infradead.org,
 bpf@...r.kernel.org, John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH v3 54/68] selftests/rseq: Drop define _GNU_SOURCE

On 2024-05-09 15:58, Edward Liaw wrote:
> _GNU_SOURCE is provided by lib.mk, so it should be dropped to prevent
> redefinition warnings.
> 
> Fixes: 809216233555 ("selftests/harness: remove use of LINE_MAX")

The patch per se looks fine, except for the "Fixes" tag.

Commit 809216233555 introduces use of asprintf in kselftest_harness.h
which is used by (all ?) selftests, including the rseq ones. However,
the rseq selftests each have the #define _GNU_SOURCE, which would have
been OK without those further changes.

So this patch is more about consolidating where the _GNU_SOURCE is
defined, which is OK with me, but not so much about "fixing" an
issue with commit 809216233555.

A "Fix" is something to be backported to stable kernels, and I
don't think this patch reaches that threshold.

If anything, this patch removes a warning that gets added by
https://lore.kernel.org/lkml/20240509200022.253089-1-edliaw@google.com/T/#mf8438d03de6e2b613da4f86d4f60c5fe1c5f8483
within the same series.

Arguably, each #define _GNU_SOURCE could have been first protected
by a #ifndef guard to eliminate this transient warning, and there
would be nothing to "fix" in this consolidation series.

Thoughts ?

Thanks,

Mathieu

> Reviewed-by: John Hubbard <jhubbard@...dia.com>
> Reviewed-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
> Signed-off-by: Edward Liaw <edliaw@...gle.com>
> ---
>   tools/testing/selftests/rseq/basic_percpu_ops_test.c | 1 -
>   tools/testing/selftests/rseq/basic_test.c            | 2 --
>   tools/testing/selftests/rseq/param_test.c            | 1 -
>   tools/testing/selftests/rseq/rseq.c                  | 2 --
>   4 files changed, 6 deletions(-)
> 
> diff --git a/tools/testing/selftests/rseq/basic_percpu_ops_test.c b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
> index 2348d2c20d0a..5961c24ee1ae 100644
> --- a/tools/testing/selftests/rseq/basic_percpu_ops_test.c
> +++ b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
> @@ -1,5 +1,4 @@
>   // SPDX-License-Identifier: LGPL-2.1
> -#define _GNU_SOURCE
>   #include <assert.h>
>   #include <pthread.h>
>   #include <sched.h>
> diff --git a/tools/testing/selftests/rseq/basic_test.c b/tools/testing/selftests/rseq/basic_test.c
> index 295eea16466f..1fed749b4bd7 100644
> --- a/tools/testing/selftests/rseq/basic_test.c
> +++ b/tools/testing/selftests/rseq/basic_test.c
> @@ -2,8 +2,6 @@
>   /*
>    * Basic test coverage for critical regions and rseq_current_cpu().
>    */
> -
> -#define _GNU_SOURCE
>   #include <assert.h>
>   #include <sched.h>
>   #include <signal.h>
> diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c
> index 2f37961240ca..48a55d94eb72 100644
> --- a/tools/testing/selftests/rseq/param_test.c
> +++ b/tools/testing/selftests/rseq/param_test.c
> @@ -1,5 +1,4 @@
>   // SPDX-License-Identifier: LGPL-2.1
> -#define _GNU_SOURCE
>   #include <assert.h>
>   #include <linux/membarrier.h>
>   #include <pthread.h>
> diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
> index 96e812bdf8a4..88602889414c 100644
> --- a/tools/testing/selftests/rseq/rseq.c
> +++ b/tools/testing/selftests/rseq/rseq.c
> @@ -14,8 +14,6 @@
>    * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>    * Lesser General Public License for more details.
>    */
> -
> -#define _GNU_SOURCE
>   #include <errno.h>
>   #include <sched.h>
>   #include <stdio.h>

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com