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Tue, 8 Sep 2026 17:34:09 -0400 (EDT) Date: Tue, 8 Sep 2026 22:34:08 +0100 From: Kiryl Shutsemau To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, rppt@kernel.org Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, usama.anjum@arm.com, usama.arif@linux.dev, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ziy@nvidia.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, vbabka@kernel.org, agordeev@linux.ibm.com, jgg@ziepe.ca, leon@kernel.org, kernel-team@meta.com Subject: Re: [PATCH v5 16/19] selftests/mm: add khugepaged race harness Message-ID: References: <20260908125105.1510704-1-kirill@shutemov.name> <20260908125105.1510704-17-kirill@shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260908125105.1510704-17-kirill@shutemov.name> X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: DD63580007 X-Stat-Signature: 46x9yw96y88gsyxigcdnr596p7ctw851 X-HE-Tag: 1788903258-420233 X-HE-Meta: U2FsdGVkX19vfKEoKCpiegz2W8PZ39r2uwB77uD7Lemd6B8yy8DFmwYc6CheXhmgNn1whgSR/YU88/3SJZu2XOq57oKLcujmPJDuY6bbaLIeokPozoR9/QT5tqqXeQvB0BQqp6WOpPVqo+DjEYBjy7ED1IhsXQ0yrtWYcuzIWqZVstE6K192VX3bQFTDTfLWK0wTeiaTH7ed8g9xPiaOhEMKiINT3HqCXkRZXnGC2QKe7fVQJyq6p0Kj5s6d0nCZsuOsr3l9iTXXLHm3PY3FTq9rDFxp/PhcJOFwm4XgHBj71RCBJoIrjHg8dVxB1y3HScwUZoJqriaS70YzGqQG/OOgbqYmXCqD75Q3i6IpPp1XiDZlI34VX9/G7iRd+xSYm3mvqeco4vPQCrz/PMg52x4/Gbn58ZxQkh7SR4J0CNLoqxd2lOiQ8YqpaX+OWoll/K1EJNm2QCNxcwHKYMJjjIJ8mn98Kg/BJQ2Y2UfgqCFeMGIlQpUM8ABue0URX/SlSzAfdtTu5EJ7iB/mMPz2XZkImwNlh62WSWZnLOPwqF04fO/sirt9p6pFlw0Pnc+xUogEiyuWQCAvLxTcA645adM5yPz9d8zRvUFwnJ+3QEvy9V90COKy7rxomZpeC9/q/o/vVv7ZpjSFHGOdnxEbEIonRlfmb6AQzbZzRsg9i6JXeqLyFP2SXnb2ApBDqNkWGgGHg1O/bmp8dlczIohIOIJ5ufdB1GdqOw1ML1NwtDU53pgUdelsrJpDIFT7tWA8a6DAcL61O9MW1wPSIhacPSqpcfyIhS61WxxBOXGVMSoNV5zVbNRzWwbkPAFJmkBPgoyR3Zx3YUejrqBsMGs/OhIuE4vE0EAC+74zcq3CgPsvKewwI9dxy7ZKYfGfbYhe6R8Levhd/lemtb1q4eP4QhvDAKomD1rjNCGblMI5Hrfbjc95TkiTpBRlAVYyI5jMITokOTfswtGwXMxx66q ar2Uy+vX B3xysLG6wKWeTgW7zSkPXXh3W4zdlXSEbRo+rhB04O5VimgnMQm1wNr7HPHCJqN/ZZG9URNhAwrN3ZH/gMrKcZ5Nr5AQIL9kcjw5Y/VWfLdG4zJFr4/X7g1n2oZPz6HJM5DCHWKh3KiwnpQAIx7Rq8PdIlT6Io8TQvDrWhZNtpi3ExmKwNvTfm/HXssoraoXhEdzR6PbuPGZIOC76MTY9ZGvzxLek4vJrf/vx2RryvbaZlTP7eNzvuMy6SmgGXVfieeYRZ7ol+24Kg7QWIWtIxbpBKQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 08, 2026 at 01:51:02PM +0100, Kiryl Shutsemau wrote: > +static void *mremapper_fn(void *arg) > +{ > + unsigned int seed = (unsigned long)arg; > + > + while (!stop) { > + void *p; > + > + p = mremap(mremap_area, hpage_pmd_size, hpage_pmd_size, > + MREMAP_MAYMOVE | MREMAP_FIXED, mremap_scratch); > + if (p == MAP_FAILED) > + ksft_exit_fail_perror("mremap() away"); > + for (int i = 0; i < 8; i++) > + mremap_scratch[(rand_r(&seed) % > + (hpage_pmd_size / page_size)) * page_size] = 1; > + p = mremap(mremap_scratch, hpage_pmd_size, hpage_pmd_size, > + MREMAP_MAYMOVE | MREMAP_FIXED, mremap_area); > + if (p == MAP_FAILED) > + ksft_exit_fail_perror("mremap() back"); > + usleep(rand_r(&seed) % 2000); > + } > + return NULL; > +} Sashiko pointed out that mremap() freed scratch area and it has to be re-reserved for next cycle. Here's fixup: diff --git a/tools/testing/selftests/mm/khugepaged_race.c b/tools/testing/selftests/mm/khugepaged_race.c index c3478b5123e2..ccfe655b3ddd 100644 --- a/tools/testing/selftests/mm/khugepaged_race.c +++ b/tools/testing/selftests/mm/khugepaged_race.c @@ -209,6 +209,11 @@ static void *mremapper_fn(void *arg) MREMAP_MAYMOVE | MREMAP_FIXED, mremap_area); if (p == MAP_FAILED) ksft_exit_fail_perror("mremap() back"); + /* The move back unmapped the scratch address: claim it again */ + if (mmap(mremap_scratch, hpage_pmd_size, PROT_NONE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, + -1, 0) != (void *)mremap_scratch) + ksft_exit_fail_perror("mmap() mremap scratch"); usleep(rand_r(&seed) % 2000); } return NULL; -- Kiryl Shutsemau / Kirill A. Shutemov