From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06DCAD30014 for ; Fri, 18 Oct 2024 14:37:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5F3276B0083; Fri, 18 Oct 2024 10:37:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5A3A96B0088; Fri, 18 Oct 2024 10:37:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 46B976B0089; Fri, 18 Oct 2024 10:37:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 27DC06B0083 for ; Fri, 18 Oct 2024 10:37:29 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id C66201208E9 for ; Fri, 18 Oct 2024 14:37:17 +0000 (UTC) X-FDA: 82686975672.13.30B8D2F Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf26.hostedemail.com (Postfix) with ESMTP id 46A0114000F for ; Fri, 18 Oct 2024 14:37:18 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1729262172; a=rsa-sha256; cv=none; b=ZmwuEU6UjDmFDNQR9GGiBk9oYWtU2CcxunaBQ6LlHIcgzNZR/VetCCgejit8yfoA9XGIn9 bye40ymhJLEHasu9/Of5lS9AIMFt6+o4zca4AEU6QKSDcpRzuz9RuD8aDLu1MZfVS9tJGM q+b4527l7Y81m3dtX6XpGDp4gK3iXBg= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1729262172; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=G4mVMGYcRdoNoylWOCrGZZb8KPJxmMclHJZdHqLOo9g=; b=urWZc9evScbe3ckYzqnDkFm16s/hpOUl19adtvDrlvpv40v4fwcHP2i3Ze5/DnZh2deuax zr/wgn3i4mC2PntlAWcQLRUZlNMq1osC+443t3KWBbe1QfXRKfRVw+xeNiiN4+Qx3twXDd Cx8FQUkLmW/9y9hIkd7yXLHvbzjlrgk= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6765FDA7; Fri, 18 Oct 2024 07:37:55 -0700 (PDT) Received: from [10.57.87.223] (unknown [10.57.87.223]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2DC163F58B; Fri, 18 Oct 2024 07:37:24 -0700 (PDT) Message-ID: Date: Fri, 18 Oct 2024 15:37:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] selftests/mm: replace atomic_bool with pthread_barrier_t Content-Language: en-GB To: Edward Liaw , linux-kselftest@vger.kernel.org, Andrew Morton , Shuah Khan , Lokesh Gidra , Peter Xu Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, linux-mm@kvack.org, Aishwarya TCV References: <20241003211716.371786-1-edliaw@google.com> <20241003211716.371786-2-edliaw@google.com> From: Ryan Roberts In-Reply-To: <20241003211716.371786-2-edliaw@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: zj9sii9g4p79u85zdxcfyna93tt1db43 X-Rspamd-Queue-Id: 46A0114000F X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1729262238-807389 X-HE-Meta: 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 rC3Ce8Rt 7e07Vq1Vdyk5SQkzz8DyZ8OdNCa9nd6WNWONpdRLbxuwQE+HjHT1zH4tx0keyfSzbo+ZruBj0H8YEBraI6prueJK8JSq6lRkHjxNBBqlsSz9SNvdHNWc1SAYaNxY56V9ilk7X8qfi0C8xqwlQmQxmjB1iY0tSa1VCngxZ6K5/UIVI4FACH0qMAr20d6oCzVU/esNd1TPDTj2vBDKbvWN5mPVurg== 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 03/10/2024 22:17, Edward Liaw wrote: > Swaps synchronization primitive with pthread_barrier, so that > stdatomic.h does not need to be included. > > The synchronization is needed on Android ARM64; we see a deadlock with > pthread_create when the parent thread races forward before the child has > a chance to start doing work. > > Fixes: 8c864371b2a1 ("selftests/mm: fix ARM related issue with fork after > pthread_create") > Signed-off-by: Edward Liaw > --- > tools/testing/selftests/mm/uffd-common.c | 5 +++-- > tools/testing/selftests/mm/uffd-common.h | 3 +-- > tools/testing/selftests/mm/uffd-unit-tests.c | 14 ++++++++------ > 3 files changed, 12 insertions(+), 10 deletions(-) > > diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c > index 717539eddf98..852e7281026e 100644 > --- a/tools/testing/selftests/mm/uffd-common.c > +++ b/tools/testing/selftests/mm/uffd-common.c > @@ -18,7 +18,7 @@ bool test_uffdio_wp = 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; > +pthread_barrier_t ready_for_fork; > > static int uffd_mem_fd_create(off_t mem_size, bool hugetlb) > { > @@ -519,7 +519,8 @@ void *uffd_poll_thread(void *arg) > pollfd[1].fd = pipefd[cpu*2]; > pollfd[1].events = POLLIN; > > - ready_for_fork = true; > + /* Ready for parent thread to fork */ > + pthread_barrier_wait(&ready_for_fork); Hi Edward, This change is causing uffd-unit-tests to hang on arm64 when running the "move on anon" test. It's happening because this wait is never returning for this case. And that happens because ready_for_fork was never initialized for this test. It looks like there are other places where a thread is created for uffd_poll_thread() where ready_for_fork is not initialized too. I added this change and it solves the problem, although it's pretty hacky. This is blocking our arm64 testing on linux-next so would appreciate either a quick fix or removing the change until a fix is ready. Thanks, Ryan ----8<----- diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c index 852e7281026e..a05eb705be02 100644 --- a/tools/testing/selftests/mm/uffd-common.c +++ b/tools/testing/selftests/mm/uffd-common.c @@ -19,6 +19,7 @@ unsigned long long *count_verify; uffd_test_ops_t *uffd_test_ops; uffd_test_case_ops_t *uffd_test_case_ops; pthread_barrier_t ready_for_fork; +bool wait_ready_for_fork; static int uffd_mem_fd_create(off_t mem_size, bool hugetlb) { @@ -520,7 +521,8 @@ void *uffd_poll_thread(void *arg) pollfd[1].events = POLLIN; /* Ready for parent thread to fork */ - pthread_barrier_wait(&ready_for_fork); + if (wait_ready_for_fork) + pthread_barrier_wait(&ready_for_fork); for (;;) { ret = poll(pollfd, 2, -1); diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h index 3e6228d8e0dc..e94329a39b34 100644 --- a/tools/testing/selftests/mm/uffd-common.h +++ b/tools/testing/selftests/mm/uffd-common.h @@ -105,6 +105,7 @@ extern bool test_uffdio_wp; extern unsigned long long *count_verify; extern volatile bool test_uffdio_copy_eexist; extern pthread_barrier_t ready_for_fork; +extern bool wait_ready_for_fork; 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/selftests/mm/uffd-unit-tests.c index 3db2296ac631..d1fc4cd6a948 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -775,6 +775,7 @@ static void uffd_sigbus_test_common(bool wp) struct uffd_args args = { 0 }; pthread_barrier_init(&ready_for_fork, NULL, 2); + wait_ready_for_fork = true; fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); @@ -794,6 +795,7 @@ static void uffd_sigbus_test_common(bool wp) /* Wait for child thread to start before forking */ pthread_barrier_wait(&ready_for_fork); pthread_barrier_destroy(&ready_for_fork); + wait_ready_for_fork = false; pid = fork(); if (pid < 0) @@ -835,6 +837,7 @@ static void uffd_events_test_common(bool wp) struct uffd_args args = { 0 }; pthread_barrier_init(&ready_for_fork, NULL, 2); + wait_ready_for_fork = true; fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); if (uffd_register(uffd, area_dst, nr_pages * page_size, @@ -848,6 +851,7 @@ static void uffd_events_test_common(bool wp) /* Wait for child thread to start before forking */ pthread_barrier_wait(&ready_for_fork); pthread_barrier_destroy(&ready_for_fork); + wait_ready_for_fork = false; pid = fork(); if (pid < 0) ----8<----- > > for (;;) { > ret = poll(pollfd, 2, -1); > diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h > index a70ae10b5f62..3e6228d8e0dc 100644 > --- a/tools/testing/selftests/mm/uffd-common.h > +++ b/tools/testing/selftests/mm/uffd-common.h > @@ -33,7 +33,6 @@ > #include > #include > #include > -#include > > #include "../kselftest.h" > #include "vm_util.h" > @@ -105,7 +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; > +extern pthread_barrier_t ready_for_fork; > > 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/selftests/mm/uffd-unit-tests.c > index b3d21eed203d..3db2296ac631 100644 > --- a/tools/testing/selftests/mm/uffd-unit-tests.c > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c > @@ -774,7 +774,7 @@ static void uffd_sigbus_test_common(bool wp) > char c; > struct uffd_args args = { 0 }; > > - ready_for_fork = false; > + pthread_barrier_init(&ready_for_fork, NULL, 2); > > fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); > > @@ -791,8 +791,9 @@ static void uffd_sigbus_test_common(bool wp) > if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) > err("uffd_poll_thread create"); > > - while (!ready_for_fork) > - ; /* Wait for the poll_thread to start executing before forking */ > + /* Wait for child thread to start before forking */ > + pthread_barrier_wait(&ready_for_fork); > + pthread_barrier_destroy(&ready_for_fork); > > pid = fork(); > if (pid < 0) > @@ -833,7 +834,7 @@ static void uffd_events_test_common(bool wp) > char c; > struct uffd_args args = { 0 }; > > - ready_for_fork = false; > + pthread_barrier_init(&ready_for_fork, NULL, 2); > > fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); > if (uffd_register(uffd, area_dst, nr_pages * page_size, > @@ -844,8 +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"); > > - while (!ready_for_fork) > - ; /* Wait for the poll_thread to start executing before forking */ > + /* Wait for child thread to start before forking */ > + pthread_barrier_wait(&ready_for_fork); > + pthread_barrier_destroy(&ready_for_fork); > > pid = fork(); > if (pid < 0)