From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-138.mta0.migadu.com [91.218.175.138]) (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 2B46F3B8D78 for ; Mon, 12 Oct 2026 10:41:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.138 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791801706; cv=none; b=IWqq18Brbokx4X3FnwLVA1LYj6opOWMfxvK7pU1CO7lr2nMrQrhDLzAamjdZ6NGtLuJ1GeVGDWQ+7n48Xrg/qkEAH5Puk5WyKkjPeh360WPAlE64vsb1H2GJcYN47qLiwsJ3+0rELHF3Ydqj4nvwjVtGF9sw48KFKpHAi+vdA9Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791801706; c=relaxed/simple; bh=o7z/TFALTSJlm+e+II+Xl9VTyQplqTg1c1dDpe0CTRQ=; h=From:To:Cc:Subject:Date:Message-Id; b=bmlrKW5rkyns66Nat9dM6hblYqYJoNx70HmWlPtMYeinsRVvIClpx33hTTX0ZSso6r4NQD/2umLs23UNP/v6QlGRLN1XzqdyJHTChiBAjfVBxcNT4mGTG/nmNKIHk0yGFg3/LV8Lh7qbjQnkd/3z8+wo714fkE5SKFYRy9jU4X8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=wGJqlQqM; arc=none smtp.client-ip=91.218.175.138 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="wGJqlQqM" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=o7z/TFALTSJlm+e+II+Xl9VTyQplqTg1c1dDpe0CTRQ=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791801702; v=1; x=1792406502; b=wGJqlQqMsdZOMq56XaNmrtXIwxLEByk9RdEgwP5EhIe52Tpqp03JM+nZ7C21os3+OVoeCkN2 Qmr0rRNgrjAtfAkqaJMWr/upSeXUjDgl+gDqmfNHgXbp14kDLvt4R887YW2rF2aZfXSAlgunUN+ zl3gEV9GauzonXkAl89ziK6o= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 7dfb80d8a1407487; Mon, 12 Oct 2026 10:41:42 +0000 X-Mizu-Trace-ID: 7dfb80d8a1407487 X-Migadu-Flow: FLOW_OUT From: Zqiang To: paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, urezki@gmail.com, boqun@kernel.org Cc: qiang.zhang@linux.dev, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] rcutorture: Clear cbflood_max for tasks-rude and srcu-atomic testing Date: Mon, 12 Oct 2026 18:41:34 +0800 Message-Id: <20261012104134.16268-1-qiang.zhang@linux.dev> X-Mailer: git-send-email 2.17.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: When running the tasks-rude and srcu-atomic tests, the fwd_prog_tasks kthread is created because the default value of fwd_progress is 1. however, the two RCU flavors not support ->call(): 1. tasks-rude: commit b428a9de9bba ("rcutorture: Stop testing RCU Tasks Rude asynchronous APIs") removed .call and .cb_barrier from tasks-rude, but left the .cbflood_max = 50000. 2. srcu-atomic: srcu_torture_init_forbidden_apis() sets ->call to NULL for SRCU_READ_FLAVOR_ATOMIC runs, but leaves ->cbflood_max untouched. In both cases, the non-zero ->cbflood_max fools the check above into creating the fwd_prog_tasks kthreads, even though those kthreads cannot possibly carry out any forward-progress test: 1. The rcu_torture_fwd_prog_cr() returns immediately due to cur_ops->call is NULL: [ 68.022674] rcu_torture_fwd_prog_cr: No ->call(), so no forward-progress test 0 [ 129.462046] rcu_torture_fwd_prog_cr: No ->call(), so no forward-progress test 0 [ 190.902123] rcu_torture_fwd_prog_cr: No ->call(), so no forward-progress test 0 [ 252.343809] rcu_torture_fwd_prog_cr: No ->call(), so no forward-progress test 0 2. The rcu_torture_fwd_prog_nr() is never even invoked, because its caller requires cur_ops->stall_dur, and neither tasks-rude nor srcu-atomic provide ->stall_dur (only rcu_ops does). Therefore, creating fwd_prog_tasks kthreads is pointless, this commit removes the .cbflood_max from tasks-rude and clears ->cbflood_max in the srcu_torture_init_forbidden_apis(). simple verification output: [ 3.062959][ T1] srcu-torture: rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test [ 2.922323][ T1] tasks-rude-torture: rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test Signed-off-by: Zqiang --- kernel/rcu/rcutorture.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 968343be4e0d..00db87256e78 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -723,6 +723,7 @@ static void srcu_torture_init_forbidden_apis(void) cur_ops->deferred_free = NULL; cur_ops->exp_current = NULL; cur_ops->start_gp_poll = NULL; + cur_ops->cbflood_max = 0; } static void srcu_torture_init(void) @@ -1250,7 +1251,6 @@ static struct rcu_torture_ops tasks_rude_ops = { .exp_sync = synchronize_rcu_tasks_rude, .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread, .get_gp_data = rcu_tasks_rude_get_gp_data, - .cbflood_max = 50000, .irq_capable = 1, .name = "tasks-rude" }; -- 2.17.1