From nobody Sun Feb 8 11:40:51 2026 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 92E57135A7A for ; Thu, 21 Mar 2024 21:37:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711057066; cv=none; b=ZXgUBBxAfRS7EGBjzuMl97QGWppnJmYldchs5+EQzuquRr608Li0FJU8W7QaFWsrJcEGXbN4L+g/Uc14NN+F6432rXId1st+h/Y/fwS9U7Ay/89yOiEQYghRdA2qxPjvalGRCc8b+qEdNTmsN534fB/qeifaUP3CNutrsgAhSXA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711057066; c=relaxed/simple; bh=17nLr5++Gj5gPnA/3LVk7GlcT9/oObVsxL2RNm5//ng=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=sLrlPEynDbLhUnvZJkg4DQdt/bU3FRakjTuYZ0wDdn6EzdxWyCg6EHskf8OGdRVD7yvBIE7+wmEzg0ZZcJwfYh6N/JjOzk29usTr+7v7dp9xvkKzEbnMeyjAEcWLZy9r4xdwUUGbVgNmLq2yohnryMu9KSJ1YDdCvNOUFl+uoaU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edliaw.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Q/iNqgs4; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edliaw.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Q/iNqgs4" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-5c6245bc7caso808031a12.3 for ; Thu, 21 Mar 2024 14:37:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1711057064; x=1711661864; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=wOtrT19asMXEr0TwJpVFoh7wEKo99GZ26en2SG6Gpmk=; b=Q/iNqgs4gw6lX/aGYhbdqFjzv2Zp4SvBhyy/Dhmv61Nz0VUXGys7OgTSKGFv5bHggf 5aaMe6tide4/m0qheZ6hMgoLqat3gCjHbmix6aJHTfg2rrKl0g2j/c19kFpcjzg55FTA 71Bk5VAwbqSHWu6FBNEK8L6OOp2/PVSecyUEbwxQySJLFJDV9t8urTQydvlIrdsPUPrR fED4EmoB32ADBfasfNVYFvE6eVogrfQG9VWS0o25XMXHTrDHHkXjerPcRmiUFWJcyLw+ vZKpMq85kQEGDJKJh1UyIgVesA8MOA/m7oLo54+8YgNBo2nfUT5rT0tXAIGMyObp+ogH slVA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1711057064; x=1711661864; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=wOtrT19asMXEr0TwJpVFoh7wEKo99GZ26en2SG6Gpmk=; b=fWxDmL0W58LZ4uih1Vu+nBqksqLLgHvjvHIaT5WYZanCK58/9zPXdy9UwaeG8i6wry T1R0ozsskr4GDjO1kQbUioOIyubtOIcXXzKn3TTEA6GMRdSovhzWRV1LGv1o28KZhxAx tPjuQOsJn+vUHbVSoXUfxJ3uVhcMXaIXb9txZ3L70iZo3iUXQITRoAQ6IQFqUMYvo71D LeQxBqlrswATonl6pindvImvicVZ0WcBTAdQBLtxIZi5FhcPTM9qSPHWioiAcprQ76Be R3GgSMyVyems+MupDUI7zgeaEO0h3FGniKxvJdpTAPpKQqP5WVF+WZFmYyy7Fb/UmiVb SUXw== X-Gm-Message-State: AOJu0Yy4trmHiM3guZWh8P5+uMT087j6EsFMXRjZ3G004FBRyd9OVDsS H0DmD0trGyMAsQYzOFGJOFHTExkZ5lCHvG72jNjrWZE/LX7xUZaN989vnYJ67w52vXLG+CPBR/5 WEx3gIHaJIRvrhncobBN/LgK8239iIBzBZmLj2u4OALoS/DuELJmVL9338ynVj0Nz/Xn0Jqnsoc bOCrx5bEpWB/AJxgcNz8O8vj6ssZaL0hxxytMl3W+F X-Google-Smtp-Source: AGHT+IFG44GRpyLSoCdzTAgGOvr+Ykn7xEnNSiVaxpdqGc3Wa47XGjUxz3BVE+W4nqXyifeoqem9jdAgDIM= X-Received: from edliaw.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:305d]) (user=edliaw job=sendgmr) by 2002:a63:f1e:0:b0:5d5:1e4d:c845 with SMTP id e30-20020a630f1e000000b005d51e4dc845mr1288pgl.10.1711057063490; Thu, 21 Mar 2024 14:37:43 -0700 (PDT) Date: Thu, 21 Mar 2024 21:37:38 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.44.0.396.g6e790dbe36-goog Message-ID: <20240321213738.1705396-1-edliaw@google.com> Subject: [PATCH v2] uffd-unit-tests: Fix ARM related issue with fork after pthread_create From: Edward Liaw To: linux-kernel@vger.kernel.org Cc: linux-kselftest@vger.kernel.org, kernel-team@android.com, Edward Liaw , Lokesh Gidra Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Following issue was observed while running the uffd-unit-tests selftest on ARM devices. On x86_64 no issues were detected: pthread_create followed by fork caused deadlock in certain cases wherein fork required some work to be completed by the created thread. Used synchronization to ensure that created thread's start function has started before invoking fork. Signed-off-by: Lokesh Gidra [edliaw: Refactored to use atomic_bool] Signed-off-by: Edward Liaw --- tools/testing/selftests/mm/uffd-common.c | 3 +++ tools/testing/selftests/mm/uffd-common.h | 2 ++ tools/testing/selftests/mm/uffd-unit-tests.c | 10 ++++++++++ 3 files changed, 15 insertions(+) diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selft= ests/mm/uffd-common.c index b0ac0ec2356d..7ad6ba660c7d 100644 --- a/tools/testing/selftests/mm/uffd-common.c +++ b/tools/testing/selftests/mm/uffd-common.c @@ -18,6 +18,7 @@ bool test_uffdio_wp =3D true; unsigned long long *count_verify; uffd_test_ops_t *uffd_test_ops; uffd_test_case_ops_t *uffd_test_case_ops; +atomic_bool ready_for_fork; =20 static int uffd_mem_fd_create(off_t mem_size, bool hugetlb) { @@ -518,6 +519,8 @@ void *uffd_poll_thread(void *arg) pollfd[1].fd =3D pipefd[cpu*2]; pollfd[1].events =3D POLLIN; =20 + ready_for_fork =3D true; + for (;;) { ret =3D poll(pollfd, 2, -1); if (ret <=3D 0) { diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selft= ests/mm/uffd-common.h index cb055282c89c..cc5629c3d2aa 100644 --- a/tools/testing/selftests/mm/uffd-common.h +++ b/tools/testing/selftests/mm/uffd-common.h @@ -32,6 +32,7 @@ #include #include #include +#include =20 #include "../kselftest.h" #include "vm_util.h" @@ -103,6 +104,7 @@ extern bool map_shared; extern bool test_uffdio_wp; extern unsigned long long *count_verify; extern volatile bool test_uffdio_copy_eexist; +extern atomic_bool ready_for_fork; =20 extern uffd_test_ops_t anon_uffd_test_ops; extern uffd_test_ops_t shmem_uffd_test_ops; diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/s= elftests/mm/uffd-unit-tests.c index 2b9f8cc52639..4a48dc617c6b 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -775,6 +775,8 @@ static void uffd_sigbus_test_common(bool wp) char c; struct uffd_args args =3D { 0 }; =20 + ready_for_fork =3D false; + fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); =20 if (uffd_register(uffd, area_dst, nr_pages * page_size, @@ -790,6 +792,9 @@ static void uffd_sigbus_test_common(bool wp) if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) err("uffd_poll_thread create"); =20 + while (!ready_for_fork) + ; /* Wait for the poll_thread to start executing before forking */ + pid =3D fork(); if (pid < 0) err("fork"); @@ -829,6 +834,8 @@ static void uffd_events_test_common(bool wp) char c; struct uffd_args args =3D { 0 }; =20 + ready_for_fork =3D false; + fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); if (uffd_register(uffd, area_dst, nr_pages * page_size, true, wp, false)) @@ -838,6 +845,9 @@ static void uffd_events_test_common(bool wp) if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) err("uffd_poll_thread create"); =20 + while (!ready_for_fork) + ; /* Wait for the poll_thread to start executing before forking */ + pid =3D fork(); if (pid < 0) err("fork"); --=20 2.44.0.396.g6e790dbe36-goog