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McKenney" , Boqun Feng Cc: RCU , LKML , Frederic Weisbecker , Cheung Wall , Neeraj upadhyay , Joel Fernandes , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH v4 1/3] rcutorture: Allow a negative value for nfakewriters Date: Thu, 27 Feb 2025 14:16:11 +0100 Message-Id: <20250227131613.52683-1-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Currently "nfakewriters" parameter can be set to any value but there is no possibility to adjust it automatically based on how many CPUs a system has where a test is run on. To address this, if the "nfakewriters" is set to negative it will be adjusted to num_online_cpus() during torture initialization. Reviewed-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/rcutorture.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index e01c0022c175..65095664f5c5 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -148,6 +148,7 @@ MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)"); static int nrealnocbers; static int nrealreaders; +static int nrealfakewriters; static struct task_struct *writer_task; static struct task_struct **fakewriter_tasks; static struct task_struct **reader_tasks; @@ -1763,7 +1764,7 @@ rcu_torture_fakewriter(void *arg) do { torture_hrtimeout_jiffies(torture_random(&rand) % 10, &rand); if (cur_ops->cb_barrier != NULL && - torture_random(&rand) % (nfakewriters * 8) == 0) { + torture_random(&rand) % (nrealfakewriters * 8) == 0) { cur_ops->cb_barrier(); } else { switch (synctype[torture_random(&rand) % nsynctypes]) { @@ -2582,7 +2583,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag) "nocbs_nthreads=%d nocbs_toggle=%d " "test_nmis=%d " "preempt_duration=%d preempt_interval=%d\n", - torture_type, tag, nrealreaders, nfakewriters, + torture_type, tag, nrealreaders, nrealfakewriters, stat_interval, verbose, test_no_idle_hz, shuffle_interval, stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter, test_boost, cur_ops->can_boost, @@ -3658,7 +3659,7 @@ rcu_torture_cleanup(void) rcu_torture_reader_mbchk = NULL; if (fakewriter_tasks) { - for (i = 0; i < nfakewriters; i++) + for (i = 0; i < nrealfakewriters; i++) torture_stop_kthread(rcu_torture_fakewriter, fakewriter_tasks[i]); kfree(fakewriter_tasks); @@ -4080,6 +4081,14 @@ rcu_torture_init(void) rcu_torture_init_srcu_lockdep(); + if (nfakewriters >= 0) { + nrealfakewriters = nfakewriters; + } else { + nrealfakewriters = num_online_cpus() - 2 - nfakewriters; + if (nrealfakewriters <= 0) + nrealfakewriters = 1; + } + if (nreaders >= 0) { nrealreaders = nreaders; } else { @@ -4136,8 +4145,9 @@ rcu_torture_init(void) writer_task); if (torture_init_error(firsterr)) goto unwind; - if (nfakewriters > 0) { - fakewriter_tasks = kcalloc(nfakewriters, + + if (nrealfakewriters > 0) { + fakewriter_tasks = kcalloc(nrealfakewriters, sizeof(fakewriter_tasks[0]), GFP_KERNEL); if (fakewriter_tasks == NULL) { @@ -4146,7 +4156,7 @@ rcu_torture_init(void) goto unwind; } } - for (i = 0; i < nfakewriters; i++) { + for (i = 0; i < nrealfakewriters; i++) { firsterr = torture_create_kthread(rcu_torture_fakewriter, NULL, fakewriter_tasks[i]); 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Thu, 27 Feb 2025 05:16:15 -0800 (PST) From: "Uladzislau Rezki (Sony)" To: "Paul E . McKenney" , Boqun Feng Cc: RCU , LKML , Frederic Weisbecker , Cheung Wall , Neeraj upadhyay , Joel Fernandes , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH v4 2/3] rcu: Update TREE05.boot to test normal synchronize_rcu() Date: Thu, 27 Feb 2025 14:16:12 +0100 Message-Id: <20250227131613.52683-2-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250227131613.52683-1-urezki@gmail.com> References: <20250227131613.52683-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add extra parameters for rcutorture module. One is the "nfakewriters" which is set -1. There will be created number of test-kthreads which correspond to number of CPUs in a test system. Those threads randomly invoke synchronize_rcu() call. Apart of that "rcu_normal" is set to 1, because it is specifically for a normal synchronize_rcu() testing, also a newly added parameter which is "rcu_normal_wake_from_gp" is set to 1 also. That prevents interaction with other callbacks in a system. Reviewed-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- tools/testing/selftests/rcutorture/configs/rcu/TREE05.boot | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE05.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE05.boot index c419cac233ee..54f5c9053474 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE05.boot +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE05.boot @@ -2,3 +2,9 @@ rcutree.gp_preinit_delay=3 rcutree.gp_init_delay=3 rcutree.gp_cleanup_delay=3 rcupdate.rcu_self_test=1 + +# This part is for synchronize_rcu() testing +rcutorture.nfakewriters=-1 +rcutorture.gp_sync=1 +rcupdate.rcu_normal=1 +rcutree.rcu_normal_wake_from_gp=1 From patchwork Thu Feb 27 13:16:13 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Uladzislau Rezki X-Patchwork-Id: 13994437 Received: from mail-lf1-f47.google.com (mail-lf1-f47.google.com [209.85.167.47]) (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 18F6222F38E; 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Thu, 27 Feb 2025 05:16:17 -0800 (PST) Received: from pc638.lan ([2001:9b1:d5a0:a500:2d8:61ff:fec9:d743]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54944174505sm157011e87.37.2025.02.27.05.16.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Feb 2025 05:16:16 -0800 (PST) From: "Uladzislau Rezki (Sony)" To: "Paul E . McKenney" , Boqun Feng Cc: RCU , LKML , Frederic Weisbecker , Cheung Wall , Neeraj upadhyay , Joel Fernandes , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH v4 3/3] rcu: Use _full() API to debug synchronize_rcu() Date: Thu, 27 Feb 2025 14:16:13 +0100 Message-Id: <20250227131613.52683-3-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250227131613.52683-1-urezki@gmail.com> References: <20250227131613.52683-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Switch for using of get_state_synchronize_rcu_full() and poll_state_synchronize_rcu_full() pair to debug a normal synchronize_rcu() call. Just using "not" full APIs to identify if a grace period is passed or not might lead to a false-positive kernel splat. It can happen, because get_state_synchronize_rcu() compresses both normal and expedited states into one single unsigned long value, so a poll_state_synchronize_rcu() can miss GP-completion when synchronize_rcu()/synchronize_rcu_expedited() concurrently run. To address this, switch to poll_state_synchronize_rcu_full() and get_state_synchronize_rcu_full() APIs, which use separate variables for expedited and normal states. Link: https://lore.kernel.org/lkml/Z5ikQeVmVdsWQrdD@pc636/T/ Fixes: 988f569ae041 ("rcu: Reduce synchronize_rcu() latency") Reported-by: cheung wall Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Paul E. McKenney Reviewed-by: Frederic Weisbecker Reviewed-by: Joel Fernandes (Google) Tested-by: Uladzislau Rezki (Sony) Signed-off-by: Boqun Feng Reviewed-by: Joel Fernandes (Google) Reviewed-by: Joel Fernandes --- include/linux/rcupdate_wait.h | 3 +++ kernel/rcu/tree.c | 8 +++----- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h index f9bed3d3f78d..4c92d4291cce 100644 --- a/include/linux/rcupdate_wait.h +++ b/include/linux/rcupdate_wait.h @@ -16,6 +16,9 @@ struct rcu_synchronize { struct rcu_head head; struct completion completion; + + /* This is for debugging. */ + struct rcu_gp_oldstate oldstate; }; void wakeme_after_rcu(struct rcu_head *head); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8625f616c65a..48384fa2eaeb 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1632,12 +1632,10 @@ static void rcu_sr_normal_complete(struct llist_node *node) { struct rcu_synchronize *rs = container_of( (struct rcu_head *) node, struct rcu_synchronize, head); - unsigned long oldstate = (unsigned long) rs->head.func; WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && - !poll_state_synchronize_rcu(oldstate), - "A full grace period is not passed yet: %lu", - rcu_seq_diff(get_state_synchronize_rcu(), oldstate)); + !poll_state_synchronize_rcu_full(&rs->oldstate), + "A full grace period is not passed yet!\n"); /* Finally. */ complete(&rs->completion); @@ -3247,7 +3245,7 @@ static void synchronize_rcu_normal(void) * snapshot before adding a request. */ if (IS_ENABLED(CONFIG_PROVE_RCU)) - rs.head.func = (void *) get_state_synchronize_rcu(); + get_state_synchronize_rcu_full(&rs.oldstate); rcu_sr_normal_add_req(&rs);