From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.253 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792748244; b=hxQeX8rz+4VKnYu2rJMD60zLjP3YBfBf7hKwt93xN2QImxwHns41dY3sLFaYAUOdZYuL 4jnTVzDULVhEY5XAcO9BZQiI6FcEUzHCBmlbpGxKpcTXmtVFI3/tngu8G+SdNg/lNqdqp 2kRd343dgaYxv814o90SThCunenzggjpbvwcelgdbQiTmfA7GWcRzmQLrbaxPfgAQgifP 0arDY50+vwlHYVsQt7cOjVhnGRMXlzdcBMsKlh5ioyUbl7kcVoKGcKisjwC42s03OmL9A YBInNUh65+gO/mXo37yr2dlTORy1yeTYLQFS+L5RNmanf7/P/EdvBMKae3b2uzrbB5w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792748244; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-Id: X-Mailer; bh=pybXVhZhBi2T1QqTyBMkUK4T7YKg68mq8AEQc+l2iHo=; b=Zpv+lXiZffwXNvdVccX7DMUzXN+END4xmhBNkYk/c9pzyy6rTIb5R8tT5aEhbz16w7Bz ZcSjFVzpVcKELmE8o2YtI32RXROXC4KB+IzUk9PelIiZ31QD5cdfv7iSatZCZga96TMrO iblCmfCzDIPhSo4dgVnHrG7lmXYpQiUF8g9KPxDmqpQMKyTysTmd0PY0X+ow59Sr+vlr6 Otn0if+cDU7utjN0upv3SOQsoYep56avYZbkywls73TgFhgpHp5lU0fbLVQyyXuNKUo0I bsUqtKHRQVFPPmj4AWcISUTVF+LqnTUR8ubtX3C4IgNjwVvG22ST61xpbuS0b3T7CNA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b="nkCh/YJT"; arc=none smtp.remote-ip=95.215.58.253 Received: from mta1.migadu.com (out-253.mta1.migadu.com [95.215.58.253]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6989E606A322 for ; Fri, 23 Oct 2026 09:37:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 6989E606A322 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, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=nkCh/YJT X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=IJyVqD6O38pH1RxzuuYvD5tOHAW4ZQ52I22UXDLS++w=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792748240; v=1; x=1793353040; b=nkCh/YJT/9NwdNFsEanOcNFyTA2XDNUftF2osfiVLUK3hmFWQ8ZFu+Z0Wokklyrjq8at4PLN +Xjk078k31nvhSmJfqoTbOeC/Qpzw3GngIfJ5bmHsclPSXr0aKrKr5d6sWHfk6Kq2nIXBgsWmkl y0ROGQ2SSCAb+svJM+491w5k= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 92fa53b973cb4534; Fri, 23 Oct 2026 09:37:20 +0000 X-Mizu-Trace-ID: 92fa53b973cb4534 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 v2] rcutorture: Avoid create fwd_prog_tasks for tasks-rude and srcu-atomic Date: Fri, 23 Oct 2026 17:37:16 +0800 Message-Id: <20261023093716.25717-1-qiang.zhang@linux.dev> X-Mailer: git-send-email 2.17.1 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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 adds ->call and ->cb_barrier to the forward-progress check, rejecting flavors that lack the cbflood_max set and a positive ->stall_dur. 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 Suggested-by: Joel Fernandes Signed-off-by: Zqiang --- kernel/rcu/rcutorture.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 968343be4e0d..92ff197f4789 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -4007,9 +4007,8 @@ static int __init rcu_torture_fwd_prog_init(void) } else if (fwd_progress < 0) { fwd_progress = nr_cpu_ids; } - if ((!cur_ops->sync && !cur_ops->call) || - (!cur_ops->cbflood_max && (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0)) || - cur_ops == &rcu_busted_ops) { + if (!cur_ops->sync || ((!cur_ops->call || !cur_ops->cb_barrier || !cur_ops->cbflood_max) && + (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0))) { VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test"); fwd_progress = 0; return 0; -- 2.17.1