From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 37FEE2D5932 for ; Fri, 28 Aug 2026 19:05:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787943950; cv=none; b=QRv4yZRwPf0kIO7L3MMfLmFr7tfEtFhdo6tPDDlE0dNZG+zCFTiBsNaZq6bmP3B7rzVuuJ2J5BRNufwmfvtpGJdYYbOxWBaBkBUiKWHiJbkeAOMYcLKTrB6QFc3OBnbOnGudYcKXRRwl7QZH2DS6Gt6QR1/ux4T7qeUUnRHY6qM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787943950; c=relaxed/simple; bh=px3vbFzfLQee2eP68A0/sM2nW4+W5uBiwPLNhV4g3Fo=; h=Date:To:From:Subject:Message-Id; b=QYnGFlALOrVua0vlhJHggu5ULqrizXWkTFpHsKZEX9Vt9oTpgPM3l5WxvShITkUKMp7MuQtvVXyvWyaV+Jnpj5pkwaH48Owx0+eewpYKb1NMsWwa2kQpNgHo1QCBsyaBl10lQ51srBH/Vv7rFRUyMSWFJkay+EV/YmALwN84eas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=MPQGltek; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="MPQGltek" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BF8E1F000E9; Fri, 28 Aug 2026 19:05:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1787943948; bh=J3TUjWuymc1T4WDfLsm1wIV0SJlmxrtPjA0Dw8WdImw=; h=Date:To:From:Subject; b=MPQGltekWXT54IBk7m5/lM9J36JWSMf8eTbMxj/SZQFiu2+aHCtQy0BbzRhhK0qV/ gOtMEnRU0QSoyPeHYZVlFPsp4xZoLmqJ4jLyIzR0w4LcPjZVa91yIRXWdDBsL1lN2N j8Dd2hFY9w+BnDEzCFAVuGaVQAG+zqb9TfQOXeE0= Date: Fri, 28 Aug 2026 12:05:48 -0700 To: mm-commits@vger.kernel.org,tj@kernel.org,shuah@kernel.org,nphamcs@gmail.com,mkoutny@suse.com,hannes@cmpxchg.org,chengming.zhou@linux.dev,wfelipe@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + selftests-cgroup-test_zswap-wait-for-cgroup-to-unpopulate-in-test_zswap_writeback.patch added to mm-new branch Message-Id: <20260828190548.9BF8E1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: selftests/cgroup: test_zswap: wait for cgroup to unpopulate in test_zswap_writeback has been added to the -mm mm-new branch. Its filename is selftests-cgroup-test_zswap-wait-for-cgroup-to-unpopulate-in-test_zswap_writeback.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-cgroup-test_zswap-wait-for-cgroup-to-unpopulate-in-test_zswap_writeback.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Wilson Felipe Pereira Subject: selftests/cgroup: test_zswap: wait for cgroup to unpopulate in test_zswap_writeback Date: Fri, 28 Aug 2026 03:37:31 +0000 Patch series "selftests/cgroup: fixes for test_zswap on single core VM", v4. This series fixes two test failures in test_zswap observed when running on a single-core VM (-smp 1) with 4GB of RAM. Patch 1 addresses a race condition in test_zswap_writeback() where waitpid() returns before the exiting child process is switched away by the kernel, causing an immediate write of "+memory" to cgroup.subtree_control to fail with -EBUSY. We fix this by waiting for cgroup.events to report "populated 0". Patch 2 fixes an implicit unsigned conversion bug in test_no_kmem_bypass() where small negative timing differences between debugfs stored_pages and cgroup zswapped bytes caused the comparison to falsely fail due to unsigned promotion. This patch (of 2): When running test_zswap on a single-core VM (-smp 1) with 4GB of RAM, test_zswap_writeback intermittently fails on the initial run after boot. In test_zswap_writeback(), after waitpid() reaps the child process created by test_zswap_writeback_one(), writing "+memory" to cgroup.subtree_control can fail with -EBUSY. Under cgroup v2, enabling domain subtree controllers is forbidden while any tasks remain in cgroup.procs. When a child process exits, exit_notify() wakes the parent process, allowing waitpid() to return immediately. However, the cgroup populated task count (nr_populated_csets) is only decremented when the exiting task is switched away via finish_task_switch() -> cgroup_task_dead(). On single-core systems, the parent runs before the dead child has been switched out, causing "+memory" to fail with -EBUSY if written immediately after waitpid() returns. Fix this by waiting for cgroup.events to report "populated 0\n" via cg_read_strcmp_wait() before enabling subtree control. Link: https://lore.kernel.org/20260828033741.2184560-1-wfelipe@google.com Link: https://lore.kernel.org/20260828033741.2184560-2-wfelipe@google.com Signed-off-by: Wilson Felipe Pereira Acked-by: Michal Koutný Cc: Chengming Zhou Cc: Johannes Weiner Cc: Nhat Pham Cc: Shuah Khan Cc: Tejun Heo Signed-off-by: Andrew Morton --- tools/testing/selftests/cgroup/test_zswap.c | 2 ++ 1 file changed, 2 insertions(+) --- a/tools/testing/selftests/cgroup/test_zswap.c~selftests-cgroup-test_zswap-wait-for-cgroup-to-unpopulate-in-test_zswap_writeback +++ a/tools/testing/selftests/cgroup/test_zswap.c @@ -408,6 +408,8 @@ static int test_zswap_writeback(const ch * Thus, the parent's setting shall be what's in effect. */ if (cg_write(test_group, "memory.zswap.max", "max")) goto out; + if (cg_read_strcmp_wait(test_group, "cgroup.events", "populated 0\n")) + goto out; if (cg_write(test_group, "cgroup.subtree_control", "+memory")) goto out; _ Patches currently in -mm which might be from wfelipe@google.com are selftests-cgroup-test_zswap-wait-for-cgroup-to-unpopulate-in-test_zswap_writeback.patch selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch