From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.mainlining.org (mail.mainlining.org [5.75.144.95]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9147B495022; Mon, 12 Oct 2026 14:50:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=5.75.144.95 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791816611; cv=none; b=WA8fY4s/4r9JKYn15JXAZVtz6URoYejlvMzkLlozaIh/FPt3M0cWUfoWCKGB/SIR1mASYnM4BjhusCrXlcWGlThKAvnTqPE9uALjykcRy3RBVv5hQv2S73tKeSP2l1ovDzvWiFXteEmy0VD28L0hGtTKqHJQonk3l4J4FCw1qb4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791816611; c=relaxed/simple; bh=ojlWEdTYH85IupYSdx+gfD5KiVSkj/6N624919m3v+A=; h=Date:From:To:CC:Subject:In-Reply-To:Message-ID:MIME-Version: Content-Type; b=tSi1oXiwZMOcYIfMvITsOGDDD2EkeC5NOaDEHjZmaE98gZN+6cARcepBZEzDyNewZwwvbwBcHwALh1bryJRALXyfIMprHkf9uUBha8W4gIGLloEDVgyh3CnZhGMqKvhMFZDLeGKw8GJGxZKrORYnvjwZwYAz1YkZof7LAenLLgg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org; spf=pass smtp.mailfrom=mainlining.org; dkim=pass (2048-bit key) header.d=mainlining.org header.i=@mainlining.org header.b=EBOJWke6; dkim=permerror (0-bit key) header.d=mainlining.org header.i=@mainlining.org header.b=qDeWqptg; arc=none smtp.client-ip=5.75.144.95 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mainlining.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mainlining.org header.i=@mainlining.org header.b="EBOJWke6"; dkim=permerror (0-bit key) header.d=mainlining.org header.i=@mainlining.org header.b="qDeWqptg" DKIM-Signature: v=1; a=rsa-sha256; s=202507r; d=mainlining.org; c=relaxed/relaxed; h=Message-ID:Subject:To:From:Date; t=1791816603; bh=J2a6KtlKXaupIikV0psaf1D FdBBvOwkAXf/qL/tKI/o=; b=EBOJWke6bO3lfrr5vCCEScZxRiNNnn7BUfiZcUvQYpUNB0Qiqx cr3FO8OqlwbCYrUi6OMoItrPvl1lnmC/83fH0LzqLqbjNCn3HMt8LMbjBs5eN+4zG9A3BDZ4a41 cdAR+zDjSoAY9Bj9B25hYxNvAOT/3Z/uJWxG8BNZWD/UXrZD8ZQbLdksKC6SPu0tp/3bpUSTUqO ljvOj1f3Sl0f0zHDmaGT1TSBGoC6KlSKbag4d6ossXTjfrmAk8atxQylEWxaYHyAhCuphya2c30 J5KtfA0YdbnCCUzmJlKHTLbYxLFd/q8w6sUzwuU/YjKytrcls0UVIdvaVeUq3I00gnQ==; DKIM-Signature: v=1; a=ed25519-sha256; s=202507e; d=mainlining.org; c=relaxed/relaxed; h=Message-ID:Subject:To:From:Date; t=1791816603; bh=J2a6KtlKXaupIikV0psaf1D FdBBvOwkAXf/qL/tKI/o=; b=qDeWqptgJpz3d+0jRuAUhUJ4/EUQRdsRrx4tTjG+04yYDT45/d rvmWqLJPcgnODe4DDWM3osut1TMGFqM0OTAA==; Date: Mon, 12 Oct 2026 15:50:04 +0100 From: Bradley Morgan To: qiang.zhang@linux.dev CC: boqun@kernel.org, frederic@kernel.org, joelagnelf@nvidia.com, linux-kernel@vger.kernel.org, neeraj.upadhyay@kernel.org, paulmck@kernel.org, rcu@vger.kernel.org, urezki@gmail.com Subject: =?US-ASCII?Q?Re=3A_=5BPATCH=5D_rcutorture=3A_Clear_cbflood=5Fma?= =?US-ASCII?Q?x_for_tasks-rude_and_srcu-atomic_testing?= In-Reply-To: <20261012104134.16268-1-qiang.zhang@linux.dev> Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit On 12 October 2026 11:41:34 BST, Zqiang wrote: >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 Fixes tag? This LGTM anyway so: Reviewed-by: Bradley Morgan > >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" > }; > --- Thanks! "I'm not a very positive person" - Linus torvalds