From nobody Tue Oct 7 15:01:46 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DEA16292B5B; Wed, 9 Jul 2025 10:43:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752057823; cv=none; b=P60gyfBeDI47sLpvtBTNiFfU4fm/IERU5aSSTgIIxmxbZJwyiw8ZyfTOhavpgb6lC3XWD0d+eJwYp/6sV1rWlNhGfu/aLkVK614kET4h0oumbZ3CFxj8xYUz9lqzPxxntC/uxcJ4HTSKg7RZvyUdBJXP5DOq3/UXYnl425CNoT0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752057823; c=relaxed/simple; bh=rlpZsvOHlInyJAVqjUW/0651NDCFnnRESbttLKrNIQY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ODG0aLWCTeDA4AVTR5b0lBEieR3ruev1vIUKLRoQmR+ZiYz80k9NIbzp831GVqr43eIJaMs0XLPxvUfsP5zzKS+SZsYYr9KrpVZbGtN9qVLv2iA2u9Xz28UUsVSJ9K9fKryg3Z6sWwph10vwwDdXGcdkToavcWzfFYj9oHBpXKE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HQhgEej6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HQhgEej6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97BB6C4CEF4; Wed, 9 Jul 2025 10:43:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752057822; bh=rlpZsvOHlInyJAVqjUW/0651NDCFnnRESbttLKrNIQY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HQhgEej6pJj/OjIKG3QwFHi9giYGcplm+dsG8tPqFePRNHA8N+XRycPHipvlP7vNh G9JdKTBm2pAANWLY9gySFoSI5VVJmliYZ+FK282sv5PNTz3s9MtgSKP2Y5FH4lYskF K68sroxPmT4XbqKZlx0Z9LDOUXCpBJlQEQLCcLV2Q1CCUuzbDT87zf5CmoSDpgIhTv zLUlECTN7CU3c0UAE2tPgJ5s13r/lU/2NteJnGDUhodlhNtRk1rdDZZRdLEoSmTlkP dSuAa6FR5PalpUs4ZOFOs8GowV2Lg7RN/DS0jMeGu1MJseAcxhR7Pb7g6lhfvmaZDy IwP/Pr1H7D+IA== From: neeraj.upadhyay@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, paulmck@kernel.org, joelagnelf@nvidia.com, frederic@kernel.org, boqun.feng@gmail.com, urezki@gmail.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang1211@gmail.com, neeraj.iitr10@gmail.com, neeraj.upadhyay@amd.com, "Neeraj Upadhyay (AMD)" Subject: [PATCH rcu 12/15] rcutorture: Fix rcutorture_one_extend_check() splat in RT kernels Date: Wed, 9 Jul 2025 16:12:12 +0530 Message-Id: <20250709104215.15562-13-neeraj.upadhyay@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20250709104215.15562-1-neeraj.upadhyay@kernel.org> References: <20250709104215.15562-1-neeraj.upadhyay@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Zqiang For built with CONFIG_PREEMPT_RT=3Dy kernels, running rcutorture tests resulted in the following splat: [ 68.797425] rcutorture_one_extend_check during change: Current 0x1 To a= dd 0x1 To remove 0x0 preempt_count() 0x0 [ 68.797533] WARNING: CPU: 2 PID: 512 at kernel/rcu/rcutorture.c:1993 rcu= torture_one_extend_check+0x419/0x560 [rcutorture] [ 68.797601] Call Trace: [ 68.797602] [ 68.797619] ? lockdep_softirqs_off+0xa5/0x160 [ 68.797631] rcutorture_one_extend+0x18e/0xcc0 [rcutorture 2466dbd2ff34d= baa36049cb323a80c3306ac997c] [ 68.797646] ? local_clock+0x19/0x40 [ 68.797659] rcu_torture_one_read+0xf0/0x280 [rcutorture 2466dbd2ff34dba= a36049cb323a80c3306ac997c] [ 68.797678] ? __pfx_rcu_torture_one_read+0x10/0x10 [rcutorture 2466dbd2= ff34dbaa36049cb323a80c3306ac997c] [ 68.797804] ? __pfx_rcu_torture_timer+0x10/0x10 [rcutorture 2466dbd2ff3= 4dbaa36049cb323a80c3306ac997c] [ 68.797815] rcu-torture: rcu_torture_reader task started [ 68.797824] rcu-torture: Creating rcu_torture_reader task [ 68.797824] rcu_torture_reader+0x238/0x580 [rcutorture 2466dbd2ff34dbaa= 36049cb323a80c3306ac997c] [ 68.797836] ? kvm_sched_clock_read+0x15/0x30 Disable BH does not change the SOFTIRQ corresponding bits in preempt_count() for RT kernels, this commit therefore use softirq_count() to check the if BH is disabled. Reviewed-by: Paul E. McKenney Signed-off-by: Zqiang Signed-off-by: Joel Fernandes Signed-off-by: Neeraj Upadhyay (AMD) --- kernel/rcu/rcutorture.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 7a07b2590c27..213f23f20a64 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -471,7 +471,7 @@ rcu_read_delay(struct torture_random_state *rrsp, struc= t rt_read_seg *rtrsp) !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { started =3D cur_ops->get_gp_seq(); ts =3D rcu_trace_clock_local(); - if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK)) + if ((preempt_count() & HARDIRQ_MASK) || softirq_count()) longdelay_ms =3D 5; /* Avoid triggering BH limits. */ mdelay(longdelay_ms); rtrsp->rt_delay_ms =3D longdelay_ms; @@ -2001,7 +2001,7 @@ static void rcutorture_one_extend_check(char *s, int = curstate, int new, int old) return; =20 WARN_ONCE((curstate & (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH)) && - !(preempt_count() & SOFTIRQ_MASK), ROEC_ARGS); + !softirq_count(), ROEC_ARGS); WARN_ONCE((curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) && !(preempt_count() & PREEMPT_MASK), ROEC_ARGS); WARN_ONCE(cur_ops->readlock_nesting && @@ -2015,7 +2015,7 @@ static void rcutorture_one_extend_check(char *s, int = curstate, int new, int old) =20 WARN_ONCE(cur_ops->extendables && !(curstate & (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH)) && - (preempt_count() & SOFTIRQ_MASK), ROEC_ARGS); + softirq_count(), ROEC_ARGS); =20 /* * non-preemptible RCU in a preemptible kernel uses preempt_disable() @@ -2036,6 +2036,9 @@ static void rcutorture_one_extend_check(char *s, int = curstate, int new, int old) if (!IS_ENABLED(CONFIG_PREEMPT_RCU)) mask |=3D RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED; =20 + if (IS_ENABLED(CONFIG_PREEMPT_RT) && softirq_count()) + mask |=3D RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH; + WARN_ONCE(cur_ops->readlock_nesting && !(curstate & mask) && cur_ops->readlock_nesting() > 0, ROEC_ARGS); } --=20 2.40.1