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[66.111.4.228]) by smtp.gmail.com with ESMTPSA id m15sm6455881qta.6.2020.08.06.17.27.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Aug 2020 17:27:14 -0700 (PDT) Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailauth.nyi.internal (Postfix) with ESMTP id 2682927C0054; Thu, 6 Aug 2020 20:27:13 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute3.internal (MEProxy); Thu, 06 Aug 2020 20:27:13 -0400 X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduiedrkedugdefhecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpeffhffvuffkfhggtggujgesghdtreertddtvdenucfhrhhomhepuehoqhhunhcu hfgvnhhguceosghoqhhunhdrfhgvnhhgsehgmhgrihhlrdgtohhmqeenucggtffrrghtth gvrhhnpeehfedujeeuffejleektdegleellefgfffhhfdvhedtkeevheejiedvjeeguddu geenucfkphepuddtuddrkeeirdegjedrkeejnecuvehluhhsthgvrhfuihiivgeptdenuc frrghrrghmpehmrghilhhfrhhomhepsghoqhhunhdomhgvshhmthhprghuthhhphgvrhhs ohhnrghlihhthidqieelvdeghedtieegqddujeejkeehheehvddqsghoqhhunhdrfhgvnh hgpeepghhmrghilhdrtghomhesfhhigihmvgdrnhgrmhgv X-ME-Proxy: Received: from localhost (unknown [101.86.47.87]) by mail.messagingengine.com (Postfix) with ESMTPA id 09DBB3280059; Thu, 6 Aug 2020 20:27:10 -0400 (EDT) Date: Fri, 7 Aug 2020 08:27:05 +0800 From: Boqun Feng To: Peter Oskolkov Cc: Mathieu Desnoyers , "Paul E . McKenney" , Peter Zijlstra , linux-kernel@vger.kernel.org, Paul Turner , Chris Kennelly , Peter Oskolkov Subject: Re: [PATCH 2/2 v2] rseq/selftests: test MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU Message-ID: <20200807002705.GA889@tardis> References: <20200806170544.382140-1-posk@google.com> <20200806170544.382140-2-posk@google.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="HlL+5n6rz5pIUxbD" Content-Disposition: inline In-Reply-To: <20200806170544.382140-2-posk@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --HlL+5n6rz5pIUxbD Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Aug 06, 2020 at 10:05:44AM -0700, Peter Oskolkov wrote: > Based on Google-internal RSEQ work done by > Paul Turner and Andrew Hunter. >=20 > This patch adds a selftest for MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU. > The test quite often fails without the previous patch in this patchset, > but consistently passes with it. >=20 > Signed-off-by: Peter Oskolkov > --- > .../selftests/rseq/basic_percpu_ops_test.c | 181 ++++++++++++++++++ > 1 file changed, 181 insertions(+) >=20 > diff --git a/tools/testing/selftests/rseq/basic_percpu_ops_test.c b/tools= /testing/selftests/rseq/basic_percpu_ops_test.c > index eb3f6db36d36..147c80deac19 100644 > --- a/tools/testing/selftests/rseq/basic_percpu_ops_test.c > +++ b/tools/testing/selftests/rseq/basic_percpu_ops_test.c > @@ -3,16 +3,21 @@ > #include > #include > #include > +#include > #include > #include > #include > #include > #include > +#include > +#include > =20 > #include "rseq.h" > =20 > #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0])) > =20 > +#define MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU (1<<7) > + > struct percpu_lock_entry { > intptr_t v; > } __attribute__((aligned(128))); > @@ -289,6 +294,180 @@ void test_percpu_list(void) > assert(sum =3D=3D expected_sum); > } > =20 > +struct test_membarrier_thread_args { > + int stop; > + intptr_t percpu_list_ptr; > +}; > + > +/* Worker threads modify data in their "active" percpu lists. */ > +void *test_membarrier_worker_thread(void *arg) > +{ > + struct test_membarrier_thread_args *args =3D > + (struct test_membarrier_thread_args *)arg; > + const int iters =3D 10 * 1000 * 1000; > + int i; > + > + if (rseq_register_current_thread()) { > + fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): = %s\n", > + errno, strerror(errno)); > + abort(); > + } > + > + for (i =3D 0; i < iters; ++i) { > + while (true) { > + int cpu, ret; > + struct percpu_list *list_ptr =3D (struct percpu_list *) > + atomic_load(&args->percpu_list_ptr); > + What if the manager thread update ->percpu_list_ptr and call membarrier() here? I.e. CPU0 CPU1 list_ptr =3D atomic_load(&args->percpu_list_ptr); // read list_b =09 atomic_store(&args->percpu_list_ptr, list_a); sys_membarrier(MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU, 1); // send ipi= to restart rseq.cs on CPU1 cpu =3D rseq_cpu_start(); // start a rseq.cs and accessing list_b! The thing is, atomic_load() is an reference to ->percpu_list_ptr, which is outside the rseq.cs, simply restarting rseq doesn't kill this reference. Am I missing something subtle? Regards, Boqun > + if (!list_ptr) > + continue; /* Not yet initialized. */ > + > + cpu =3D rseq_cpu_start(); > + struct percpu_list_node *node =3D list_ptr->c[cpu].head; > + const intptr_t prev =3D node->data; > + > + ret =3D rseq_cmpeqv_cmpeqv_storev(&node->data, prev, > + &args->percpu_list_ptr, > + (intptr_t)list_ptr, prev + 1, cpu); > + if (!ret) > + break; /* Success. */ > + } > + } > + > + if (rseq_unregister_current_thread()) { > + fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d)= : %s\n", > + errno, strerror(errno)); > + abort(); > + } > + return NULL; > +} > + > +void test_membarrier_init_percpu_list(struct percpu_list *list) > +{ > + int i; > + > + memset(list, 0, sizeof(*list)); > + for (i =3D 0; i < CPU_SETSIZE; i++) { > + struct percpu_list_node *node; > + > + node =3D malloc(sizeof(*node)); > + assert(node); > + node->data =3D 0; > + node->next =3D NULL; > + list->c[i].head =3D node; > + } > +} > + > +void test_membarrier_free_percpu_list(struct percpu_list *list) > +{ > + int i; > + > + for (i =3D 0; i < CPU_SETSIZE; i++) > + free(list->c[i].head); > +} > + > +static int sys_membarrier(int cmd, int flags) > +{ > + return syscall(__NR_membarrier, cmd, flags); > +} > + > +/* > + * The manager thread swaps per-cpu lists that worker threads see, > + * and validates that there are no unexpected modifications. > + */ > +void *test_membarrier_manager_thread(void *arg) > +{ > + struct test_membarrier_thread_args *args =3D > + (struct test_membarrier_thread_args *)arg; > + struct percpu_list list_a, list_b; > + intptr_t expect_a =3D 0, expect_b =3D 0; > + int cpu_a =3D 0, cpu_b =3D 0; > + > + if (rseq_register_current_thread()) { > + fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): = %s\n", > + errno, strerror(errno)); > + abort(); > + } > + > + /* Init lists. */ > + test_membarrier_init_percpu_list(&list_a); > + test_membarrier_init_percpu_list(&list_b); > + > + atomic_store(&args->percpu_list_ptr, (intptr_t)&list_a); > + > + while (!atomic_load(&args->stop)) { > + /* list_a is "active". */ > + cpu_a =3D rand() % CPU_SETSIZE; > + /* > + * As list_b is "inactive", we should never see changes > + * to list_b. > + */ > + if (expect_b !=3D atomic_load(&list_b.c[cpu_b].head->data)) { > + fprintf(stderr, "Membarrier test failed\n"); > + abort(); > + } > + > + /* Make list_b "active". */ > + atomic_store(&args->percpu_list_ptr, (intptr_t)&list_b); > + sys_membarrier(MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU, cpu_a); > + /* > + * Cpu A should now only modify list_b, so we values > + * in list_a should be stable. > + */ > + expect_a =3D atomic_load(&list_a.c[cpu_a].head->data); > + > + cpu_b =3D rand() % CPU_SETSIZE; > + /* > + * As list_a is "inactive", we should never see changes > + * to list_a. > + */ > + if (expect_a !=3D atomic_load(&list_a.c[cpu_a].head->data)) { > + fprintf(stderr, "Membarrier test failed\n"); > + abort(); > + } > + > + /* Make list_a "active". */ > + atomic_store(&args->percpu_list_ptr, (intptr_t)&list_a); > + sys_membarrier(MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU, cpu_b); > + /* Remember a value from list_b. */ > + expect_b =3D atomic_load(&list_b.c[cpu_b].head->data); > + } > + > + test_membarrier_free_percpu_list(&list_a); > + test_membarrier_free_percpu_list(&list_b); > + > + if (rseq_unregister_current_thread()) { > + fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d)= : %s\n", > + errno, strerror(errno)); > + abort(); > + } > + return NULL; > +} > + > +/* Test MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU membarrier command. */ > +void test_membarrier(void) > +{ > + struct test_membarrier_thread_args thread_args; > + pthread_t worker_threads[CPU_SETSIZE]; > + pthread_t manager_thread; > + int i; > + > + thread_args.stop =3D 0; > + thread_args.percpu_list_ptr =3D 0; > + pthread_create(&manager_thread, NULL, > + test_membarrier_manager_thread, &thread_args); > + > + for (i =3D 0; i < CPU_SETSIZE; i++) > + pthread_create(&worker_threads[i], NULL, > + test_membarrier_worker_thread, &thread_args); > + > + for (i =3D 0; i < CPU_SETSIZE; i++) > + pthread_join(worker_threads[i], NULL); > + > + atomic_store(&thread_args.stop, 1); > + pthread_join(manager_thread, NULL); > +} > + > int main(int argc, char **argv) > { > if (rseq_register_current_thread()) { > @@ -300,6 +479,8 @@ int main(int argc, char **argv) > test_percpu_spinlock(); > printf("percpu_list\n"); > test_percpu_list(); > + printf("membarrier\n"); > + test_membarrier(); > if (rseq_unregister_current_thread()) { > fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d)= : %s\n", > errno, strerror(errno)); > --=20 > 2.28.0.163.g6104cc2f0b6-goog >=20 --HlL+5n6rz5pIUxbD Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEj5IosQTPz8XU1wRHSXnow7UH+rgFAl8sn9YACgkQSXnow7UH +rjiHQf/fJpwAY8SZvR+JcVF/c8SVaeCyYI9dfblAYjO3L/olqZ9jlr7SfDUthHs gqrNNWpLxSbStIdogWCsnm+cMcipISOyKAQABjYuCD6EL4EE0fVElt4STpu7w7Mm emsvZamuEiOyqrQY6WjU51q/O771UAfo2nqPLWGVB6dPZMALTtUxWYqTGrj6IMjL uvp7BNdVvvnqkdSvfdQDER6t//c3mvjT35si1o66FZQyOTsZujgB/j+GE/qh4vef BrOYWYVFbHi9JA2kTE+o7Hi5yVYrUFnIkCdrKVZnIvIMR7TFsshzz9iQMGKWQMa0 JbHzRewB2nPNIeBnQcc+MGLvDoIjuw== =hwwt -----END PGP SIGNATURE----- --HlL+5n6rz5pIUxbD--