linux-kernel - Re: [PATCH v3 1/8] selftests/mm: Add -Wunreachable-code and fix warnings

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Message-ID: <9e2dcf8f-98b7-4461-af75-71627ee48230@arm.com>
Date: Tue, 26 Aug 2025 10:33:59 +0200
From: Kevin Brodsky <kevin.brodsky@....com>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>,
 Shuah Khan <shuah@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>,
 Peter Xu <peterx@...hat.com>, Leon Romanovsky <leon@...nel.org>,
 Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linux-riscv@...ts.infradead.org
Cc: kernel@...labora.com, Sidhartha Kumar <sidhartha.kumar@...cle.com>
Subject: Re: [PATCH v3 1/8] selftests/mm: Add -Wunreachable-code and fix
 warnings

On 22/08/2025 10:20, Muhammad Usama Anjum wrote:
> Enable -Wunreachable-code flag to catch dead code and fix them.
>
> 1. Remove the dead code and write a comment instead:
> hmm-tests.c:2033:3: warning: code will never be executed
> [-Wunreachable-code]
>                 perror("Should not reach this\n");
>                 ^~~~~~
>
> 2. ksft_exit_fail_msg() calls exit(). Remove the dead code.

In that new version there's no dead code removal, rather that call is
replaced to a call to ksft_print_msg() that doesn't exit.

With that corrected:

Reviewed-by: Kevin Brodsky <kevin.brodsky@....com>

- Kevin

> split_huge_page_test.c:301:3: warning: code will never be executed
> [-Wunreachable-code]
>                 goto cleanup;
>                 ^~~~~~~~~~~~
>
> 3. Remove duplicate inline.
> pkey_sighandler_tests.c:44:15: warning: duplicate 'inline' declaration
> specifier [-Wduplicate-decl-specifier]
> static inline __always_inline
>
> Reviewed-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
> ---
> Changes since v2:
> - In split_huge_page_test.c, print error message and then go to cleanup
>   tag for cleanup instead of just exiting without cleanup
> ---
>  tools/testing/selftests/mm/Makefile                | 1 +
>  tools/testing/selftests/mm/hmm-tests.c             | 5 ++---
>  tools/testing/selftests/mm/pkey_sighandler_tests.c | 2 +-
>  tools/testing/selftests/mm/split_huge_page_test.c  | 2 +-
>  4 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> index d13b3cef2a2b2..23d4bf6215465 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -34,6 +34,7 @@ endif
>  MAKEFLAGS += --no-builtin-rules
>  
>  CFLAGS = -Wall -O2 -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) $(TOOLS_INCLUDES)
> +CFLAGS += -Wunreachable-code
>  LDLIBS = -lrt -lpthread -lm
>  
>  # Some distributions (such as Ubuntu) configure GCC so that _FORTIFY_SOURCE is
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 141bf63cbe05e..15aadaf24a667 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2027,11 +2027,10 @@ TEST_F(hmm, hmm_cow_in_device)
>  	if (pid == -1)
>  		ASSERT_EQ(pid, 0);
>  	if (!pid) {
> -		/* Child process waitd for SIGTERM from the parent. */
> +		/* Child process waits for SIGTERM from the parent. */
>  		while (1) {
>  		}
> -		perror("Should not reach this\n");
> -		exit(0);
> +		/* Should not reach this */
>  	}
>  	/* Parent process writes to COW pages(s) and gets a
>  	 * new copy in system. In case of device private pages,
> diff --git a/tools/testing/selftests/mm/pkey_sighandler_tests.c b/tools/testing/selftests/mm/pkey_sighandler_tests.c
> index b5e076a564c95..302fef54049c8 100644
> --- a/tools/testing/selftests/mm/pkey_sighandler_tests.c
> +++ b/tools/testing/selftests/mm/pkey_sighandler_tests.c
> @@ -41,7 +41,7 @@ static siginfo_t siginfo = {0};
>   * syscall will attempt to access the PLT in order to call a library function
>   * which is protected by MPK 0 which we don't have access to.
>   */
> -static inline __always_inline
> +static __always_inline
>  long syscall_raw(long n, long a1, long a2, long a3, long a4, long a5, long a6)
>  {
>  	unsigned long ret;
> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
> index bf40e6b121abc..de0d26f3df675 100644
> --- a/tools/testing/selftests/mm/split_huge_page_test.c
> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
> @@ -297,7 +297,7 @@ void split_file_backed_thp(int order)
>  
>  	status = snprintf(testfile, INPUT_MAX, "%s/thp_file", tmpfs_loc);
>  	if (status >= INPUT_MAX) {
> -		ksft_exit_fail_msg("Fail to create file-backed THP split testing file\n");
> +		ksft_print_msg("Fail to create file-backed THP split testing file\n");
>  		goto cleanup;
>  	}
>