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Thu, 17 Jul 2025 03:48:22 -0700 (PDT) From: wang lian To: akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, brauner@kernel.org, broonie@kernel.org, david@redhat.com, gkwang@linx-info.com, jannh@google.com, lianux.mm@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, ludovico.zy.wu@gmail.com, p1ucky0923@gmail.com, ryncsn@gmail.com, shuah@kernel.org, sj@kernel.org, vbabka@suse.cz, zijing.zhang@proton.me, ziy@nvidia.com Subject: Re: [PATCH] selftests/mm: reuse FORCE_READ to replace "asm volatile("" : "+r" (XXX));" Date: Thu, 17 Jul 2025 18:48:11 +0800 Message-ID: <20250717104811.3773-1-lianux.mm@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250716151543.998b121a58064011e9ce68cb@linux-foundation.org> References: <20250716151543.998b121a58064011e9ce68cb@linux-foundation.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 0B9EB140004 X-Stat-Signature: 7khucq8kxymrk49hhsztrtmc9e4h6mgs X-Rspam-User: X-HE-Tag: 1752749304-963436 X-HE-Meta: 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 7epVs1AD 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 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, 16 Jul 2025 20:31:26 +0800 wang lian wrote: > > Several mm selftests use the `asm volatile("" : "+r" (variable));` > > construct to force a read of a variable, preventing the compiler from > > optimizing away the memory access. This idiom is cryptic and duplicated > > across multiple test files. > > > > Following a suggestion from David[1], this patch refactors this > > common pattern into a FORCE_READ() macro > > > > tools/testing/selftests/mm/cow.c | 30 +++++++++---------- > > tools/testing/selftests/mm/hugetlb-madvise.c | 5 +--- > > tools/testing/selftests/mm/migration.c | 13 ++++---- > > tools/testing/selftests/mm/pagemap_ioctl.c | 4 +-- > > .../selftests/mm/split_huge_page_test.c | 4 +-- > > 5 files changed, 24 insertions(+), 32 deletions(-) > The patch forgot to move the FORCE_READ definition into a header? Hi Andrew, You are absolutely right. My apologies for the inconvenience. This patch was sent standalone based on a suggestion from David during the discussion of a previous, larger patch series. In that original series, I had already moved the FORCE_READ() macro definition into vm_util.h. You can find the original patch series and discussion at this link: https://lore.kernel.org/lkml/20250714130009.14581-1-lianux.mm@gmail.com/ It should also be in your mailing list archive. To make this easier to review and apply, I can send a new, small patch series that first introduces the FORCE_READ() macro in vm_util.h and then applies this refactoring. Please let me know if you'd prefer that. Sorry again for the confusion. Best regards, wang lian