From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0CE49C4332F for ; Thu, 2 Dec 2021 00:43:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354758AbhLBArH (ORCPT ); Wed, 1 Dec 2021 19:47:07 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:39200 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240641AbhLBArC (ORCPT ); Wed, 1 Dec 2021 19:47:02 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D4848B82197; Thu, 2 Dec 2021 00:43:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 835CEC53FCD; Thu, 2 Dec 2021 00:43:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638405818; bh=BwmW4ZgS1oIucAqxGoAL1piw7majEuKwklXzQUxISsM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=t8VMRg7h476Tcj7Fm5/25Xg37ryY2R0gaS5NwJUUSO4aiCQcA4ireTSqoMIg7ArIT 8ZtW0wPVU/dTtN5A+BF9zsYfmd2AYoBY95Hd4TfffR/idDaa2341FFt8abOsT9nTUE EiF1TzXyBS2ppumchM4AAdETBJYs+wsSAYFEwv6m+uuRYwQ/le9s9bCbHeFnpKFYAx GOV2Hrz5P3TP5bXm0Y62V2P8oBo78JYWi+lHVgvdL6QprRR1Y5mpMaczhd3J1h78E/ Iegc5iNrtXKLUNkH9RcOh/B7Dm/76CnVHl358/kVXNFHPjy2PvYWySwxQA4chAlOlk elZb3ZZmFqpNA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 4A5425C100F; Wed, 1 Dec 2021 16:43:38 -0800 (PST) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH rcu 02/17] rcutorture: More thoroughly test nested readers Date: Wed, 1 Dec 2021 16:43:21 -0800 Message-Id: <20211202004337.3130175-2-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20211202004245.GA3129966@paulmck-ThinkPad-P17-Gen-1> References: <20211202004245.GA3129966@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, nested readers occur only when a timer handler interrupts a reader. This is rare, and is thus insufficient testing of the transition between nesting levels. This commit therefore causes rcutorture nested readers to be the rule rather than the exception. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 73 ++++++++++++++++++++++++++++------------- 1 file changed, 50 insertions(+), 23 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 1e03fe681f025..d295da380fb4f 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -53,15 +53,18 @@ MODULE_LICENSE("GPL"); MODULE_AUTHOR("Paul E. McKenney and Josh Triplett "); /* Bits for ->extendables field, extendables param, and related definitions. */ -#define RCUTORTURE_RDR_SHIFT 8 /* Put SRCU index in upper bits. */ -#define RCUTORTURE_RDR_MASK (1 << RCUTORTURE_RDR_SHIFT) +#define RCUTORTURE_RDR_SHIFT_1 8 /* Put SRCU index in upper bits. */ +#define RCUTORTURE_RDR_MASK_1 (1 << RCUTORTURE_RDR_SHIFT_1) +#define RCUTORTURE_RDR_SHIFT_2 9 /* Put SRCU index in upper bits. */ +#define RCUTORTURE_RDR_MASK_2 (1 << RCUTORTURE_RDR_SHIFT_2) #define RCUTORTURE_RDR_BH 0x01 /* Extend readers by disabling bh. */ #define RCUTORTURE_RDR_IRQ 0x02 /* ... disabling interrupts. */ #define RCUTORTURE_RDR_PREEMPT 0x04 /* ... disabling preemption. */ #define RCUTORTURE_RDR_RBH 0x08 /* ... rcu_read_lock_bh(). */ #define RCUTORTURE_RDR_SCHED 0x10 /* ... rcu_read_lock_sched(). */ -#define RCUTORTURE_RDR_RCU 0x20 /* ... entering another RCU reader. */ -#define RCUTORTURE_RDR_NBITS 6 /* Number of bits defined above. */ +#define RCUTORTURE_RDR_RCU_1 0x20 /* ... entering another RCU reader. */ +#define RCUTORTURE_RDR_RCU_2 0x40 /* ... entering another RCU reader. */ +#define RCUTORTURE_RDR_NBITS 7 /* Number of bits defined above. */ #define RCUTORTURE_MAX_EXTEND \ (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \ RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED) @@ -1420,13 +1423,15 @@ static void rcutorture_one_extend(int *readstate, int newstate, struct rt_read_seg *rtrsp) { unsigned long flags; - int idxnew = -1; - int idxold = *readstate; + int idxnew1 = -1; + int idxnew2 = -1; + int idxold1 = *readstate; + int idxold2 = idxold1; int statesnew = ~*readstate & newstate; int statesold = *readstate & ~newstate; - WARN_ON_ONCE(idxold < 0); - WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1); + WARN_ON_ONCE(idxold2 < 0); + WARN_ON_ONCE((idxold2 >> RCUTORTURE_RDR_SHIFT_2) > 1); rtrsp->rt_readstate = newstate; /* First, put new protection in place to avoid critical-section gap. */ @@ -1440,8 +1445,10 @@ static void rcutorture_one_extend(int *readstate, int newstate, preempt_disable(); if (statesnew & RCUTORTURE_RDR_SCHED) rcu_read_lock_sched(); - if (statesnew & RCUTORTURE_RDR_RCU) - idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT; + if (statesnew & RCUTORTURE_RDR_RCU_1) + idxnew1 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_1; + if (statesnew & RCUTORTURE_RDR_RCU_2) + idxnew2 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_2; /* * Next, remove old protection, in decreasing order of strength @@ -1460,13 +1467,19 @@ static void rcutorture_one_extend(int *readstate, int newstate, local_bh_enable(); if (statesold & RCUTORTURE_RDR_RBH) rcu_read_unlock_bh(); - if (statesold & RCUTORTURE_RDR_RCU) { + if (statesold & RCUTORTURE_RDR_RCU_2) { + cur_ops->readunlock((idxold2 >> RCUTORTURE_RDR_SHIFT_2) & 0x1); + WARN_ON_ONCE(idxnew2 != -1); + idxold2 = 0; + } + if (statesold & RCUTORTURE_RDR_RCU_1) { bool lockit = !statesnew && !(torture_random(trsp) & 0xffff); if (lockit) raw_spin_lock_irqsave(¤t->pi_lock, flags); - cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT); - idxold = 0; + cur_ops->readunlock((idxold1 >> RCUTORTURE_RDR_SHIFT_1) & 0x1); + WARN_ON_ONCE(idxnew1 != -1); + idxold1 = 0; if (lockit) raw_spin_unlock_irqrestore(¤t->pi_lock, flags); } @@ -1476,13 +1489,19 @@ static void rcutorture_one_extend(int *readstate, int newstate, cur_ops->read_delay(trsp, rtrsp); /* Update the reader state. */ - if (idxnew == -1) - idxnew = idxold & RCUTORTURE_RDR_MASK; - WARN_ON_ONCE(idxnew < 0); - WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1); - *readstate = idxnew | newstate; - WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0); - WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1); + if (idxnew1 == -1) + idxnew1 = idxold1 & RCUTORTURE_RDR_MASK_1; + WARN_ON_ONCE(idxnew1 < 0); + if (WARN_ON_ONCE((idxnew1 >> RCUTORTURE_RDR_SHIFT_1) > 1)) + pr_info("Unexpected idxnew1 value of %#x\n", idxnew1); + if (idxnew2 == -1) + idxnew2 = idxold2 & RCUTORTURE_RDR_MASK_2; + WARN_ON_ONCE(idxnew2 < 0); + WARN_ON_ONCE((idxnew2 >> RCUTORTURE_RDR_SHIFT_2) > 1); + *readstate = idxnew1 | idxnew2 | newstate; + WARN_ON_ONCE(*readstate < 0); + if (WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT_2) > 1)) + pr_info("Unexpected idxnew2 value of %#x\n", idxnew2); } /* Return the biggest extendables mask given current RCU and boot parameters. */ @@ -1492,7 +1511,7 @@ static int rcutorture_extend_mask_max(void) WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND); mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables; - mask = mask | RCUTORTURE_RDR_RCU; + mask = mask | RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2; return mask; } @@ -1507,13 +1526,21 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ; unsigned long bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH; - WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT); + WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1); /* Mostly only one bit (need preemption!), sometimes lots of bits. */ if (!(randmask1 & 0x7)) mask = mask & randmask2; else mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS)); + // Can't have nested RCU reader without outer RCU reader. + if (!(mask & RCUTORTURE_RDR_RCU_1) && (mask & RCUTORTURE_RDR_RCU_2)) { + if (oldmask & RCUTORTURE_RDR_RCU_1) + mask &= ~RCUTORTURE_RDR_RCU_2; + else + mask |= RCUTORTURE_RDR_RCU_1; + } + /* * Can't enable bh w/irq disabled. */ @@ -1533,7 +1560,7 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) mask |= oldmask & bhs; } - return mask ?: RCUTORTURE_RDR_RCU; + return mask ?: RCUTORTURE_RDR_RCU_1; } /* -- 2.31.1.189.g2e36527f23