From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 1B257311C2A; Thu, 11 Jun 2026 03:42:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781149325; cv=none; b=mQ+Wh0vrSM6YSR8znBLyfNdvpQAnHO22sYJPWbJEam9xegFJ7zWg+iretjZ+4o1yhfllGYSUBtGFsFhuXwdgoZihaHFi5HZZCFw56nVYfZjWluO47D20S/VznaBi5NPZ95ANHk1KVhntnklSXtTQsFe4bEqodzVQyobKx+dRFVo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781149325; c=relaxed/simple; bh=YCzVzW/BsPEbbOja/j02yPmWwf9lZLthupw9glrzbzg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ER2WNTJVAawlS+UoiCfqiroJa1aISZDdVELgvPREvoUaOxrUz3vMD0M5ReOcdF0uMt/WITBVRcUZDaqUV9Q/mSTxfFosjhmfEr+biN+wdgmM3IZUxF/fQAbLrfcbqIJN+Z/ZfBXpNfjJWzV+vPjd3HvDAUzjCb5UdETXPnvzt+k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=Jlzkl5Xy; arc=none smtp.client-ip=148.163.158.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="Jlzkl5Xy" Received: from pps.filterd (m0353725.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 65AJu3op1741881; Thu, 11 Jun 2026 03:41:37 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:date:from:in-reply-to:message-id :mime-version:references:subject:to; s=pp1; bh=NhRSo6Z/W4jD3irkb V2apRuLXcxRfq9kkdO+okO3Cxw=; b=Jlzkl5XyMkwM9GervKpM1nrFhbWDSq/FM rauRTRXeLZmmAK9w/NnVvDb+ru6TTkBd8TNTB3WuerAB3RaHwjep9YDEcofxUamO qIBJ1mDtd5YbyZHtk1wUxylVv1KI/PIhz9sRX7UEsctfRz3pNKwLXzVzm/Y6wr5/ VPqh/fGHygiycvMqsiynVttkRk0fMF9vb1zhHqY1/RE+476Dx4pOOZYuAK0JmSSA zqhizDcNV6XoPLAcaO/MieLCF3N1U0M6iVTXmAmRSBpwqI9J1bDRB0Ebxo0pv809 5Ya7OIGvEugGiyKYBzJW146439t7UC87zY0UtyTJAVHxVDvKYVo/A== Received: from ppma11.dal12v.mail.ibm.com (db.9e.1632.ip4.static.sl-reverse.com [50.22.158.219]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4eqe8bh80w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 11 Jun 2026 03:41:36 +0000 (GMT) Received: from pps.filterd (ppma11.dal12v.mail.ibm.com [127.0.0.1]) by ppma11.dal12v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 65B3dAjQ001974; Thu, 11 Jun 2026 03:41:35 GMT Received: from smtprelay04.fra02v.mail.ibm.com ([9.218.2.228]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 4eqe09hf7b-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 11 Jun 2026 03:41:35 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (smtpav07.fra02v.mail.ibm.com [10.20.54.106]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 65B3fVk114942694 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 11 Jun 2026 03:41:32 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D4E2A20043; Thu, 11 Jun 2026 03:41:31 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9D47820040; Thu, 11 Jun 2026 03:41:25 +0000 (GMT) Received: from aboo.ibm.com.com (unknown [9.39.27.36]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 11 Jun 2026 03:41:25 +0000 (GMT) From: Aboorva Devarajan To: Andrew Morton , linux-mm@kvack.org Cc: Jason Gunthorpe , Leon Romanovsky , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Ralph Campbell , Matthew Brost , Balbir Singh , Alistair Popple , Alex Sierra , Matthew Wilcox , Sayali Patil , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Aboorva Devarajan Subject: [PATCH v3 3/3] selftests/mm: fix exclusive_cow test fork() handling Date: Thu, 11 Jun 2026 09:11:02 +0530 Message-ID: <20260611034102.1030738-4-aboorvad@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260611034102.1030738-1-aboorvad@linux.ibm.com> References: <20260611034102.1030738-1-aboorvad@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=Xfa5Co55 c=1 sm=1 tr=0 ts=6a2a2e70 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=qerImOSnxKlIG2EQ76sA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjExMDAzMiBTYWx0ZWRfXwuBRMA9ofurN DRF9/IxvT7YfjGofRDu3rufKRwBD/EFBtft/ebk+6w3tHTYcUueien8y4OX4twbkGaaluN5AmAn zDomrsbKg/RVhlAht7kYRLV5zeZTc+//H5quTBJsJMmPuAkS/JSMEjUZ3oQn3/RKbxrBmFoD4V7 HpL0iPmy1RbIp+Xh1o+XUZs/bIgz4RCGl+NWwdvX1PbyJgZNtLoklGEFabBJ+THs4lXtkSdGFdV hMvoUE/GKK4PrLxjg1urjzD1dkD/o1DgmZl244bohffeQLRB079kPGzUtfoIMKmG7OtXdijfJmz XOrNqMX3iVvL2CdPidhljgQymQs2rg7hDkPTF+fjysrgAw0SD8g+8poZVNoP399e06sULab+Yi8 n0re2BbHaIQ6lGk5WPlVTcpBxgVgn11v0YuiP8BBimmqNGeaoHERIhyJmX3grQOTA6Ilh5FgxGR mAJ4YEaZv2QJVroaxeg== X-Proofpoint-Spam-Info: AW1haW4tMjYwNjExMDAzMiBTYWx0ZWRfX23Z/1Tm6Hdq+ n67wZ+D4GD4hpN/3qZ5ji4oLyp7WxipbR0m8fmtJGrX1HBbs5dK+u5+NRucy4Syfxv0wOlELfLA rFLyjtJ1mPpe7sxAMabF0hQWXYPesfo= X-Proofpoint-ORIG-GUID: 0LkASIrnKhk4Zh6sHYbQn9nK8TJmjTT1 X-Proofpoint-GUID: Q8hGwmMOMMTc_3yFvNLksDWfLZ7DXacl X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-11_01,2026-06-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 suspectscore=0 clxscore=1015 phishscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606040000 definitions=main-2606110032 The test ignores the return value of fork(), so both the parent and the (newly created) child run the COW verification loops and then call hmm_buffer_free() before returning into the kselftest harness, which _exit()s each side. This duplicated teardown sequence has been observed to manifest as a SIGSEGV in the test child, e.g.: hmm-tests[360141]: segfault (11) at 0 nip 10006964 lr 1000ac3c code 1 in hmm-tests[6964,10000000+30000] Fix this by adopting the same fork()-then-wait pattern already used by the nearby anon_write_child / anon_write_child_shared tests in this file: the child performs the COW verification and then _exit(0)s so it does not run the test teardown, while the parent independently verifies COW, waits for the child, and only then frees the buffer. Fixes: b659baea75469 ("mm: selftests for exclusive device memory") Signed-off-by: Aboorva Devarajan --- tools/testing/selftests/mm/hmm-tests.c | 31 +++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c index 8f4f82467043..e4c49699f3f7 100644 --- a/tools/testing/selftests/mm/hmm-tests.c +++ b/tools/testing/selftests/mm/hmm-tests.c @@ -1884,6 +1884,8 @@ TEST_F(hmm, exclusive_cow) unsigned long i; int *ptr; int ret; + pid_t pid; + int status; npages = ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift; ASSERT_NE(npages, 0); @@ -1912,14 +1914,37 @@ TEST_F(hmm, exclusive_cow) ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, npages); - fork(); + pid = fork(); + if (pid == -1) + ASSERT_EQ(pid, 0); - /* Fault pages back to system memory and check them. */ + if (pid == 0) { + /* + * Child verifies COW independently, then _exit(0)s so it does + * not run the test teardown. A failed ASSERT_* here makes the + * harness abort() the child, so the parent sees + * !WIFEXITED(status) below and fails in turn. + */ + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) + ASSERT_EQ(ptr[i]++, i); + + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) + ASSERT_EQ(ptr[i], i + 1); + + _exit(0); + } + + /* Parent: also increment to verify COW works for both processes. */ for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) ASSERT_EQ(ptr[i]++, i); for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) - ASSERT_EQ(ptr[i], i+1); + ASSERT_EQ(ptr[i], i + 1); + + /* Parent: wait for child and then free the buffer. */ + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + ASSERT_EQ(WEXITSTATUS(status), 0); hmm_buffer_free(buffer); } -- 2.54.0