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From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Jordan Niethe" <jniethe5@gmail.com>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 04/17] powerpc/qspinlock: convert atomic operations to assembly
Date: Thu, 10 Nov 2022 21:48:54 +1000	[thread overview]
Message-ID: <CO8LCA89WZYL.3APIMVZTFJ2QT@bobo> (raw)
In-Reply-To: <9226e7ca-c74b-845b-d10b-9928449a9489@csgroup.eu>

On Thu Nov 10, 2022 at 6:36 PM AEST, Christophe Leroy wrote:
>
>
> Le 10/11/2022 à 01:39, Jordan Niethe a écrit :
> >> +static __always_inline int trylock_clear_tail_cpu(struct qspinlock *lock, u32 old)
> >>   {
> >> -	int newval = _Q_LOCKED_VAL;
> >> -
> >> -	if (atomic_cmpxchg_acquire(&lock->val, val, newval) == val)
> >> +	u32 new = _Q_LOCKED_VAL;
> >> +	u32 prev;
> >> +
> >> +	BUG_ON(old & _Q_LOCKED_VAL);
> > 
> > The BUG_ON() could have been introduced in an earlier patch I think.
>
> Can we avoid the BUG_ON() at all and replace by a WARN_ON ?

Lock has gone wrong here. Critical sections not working means data
corruption and little prospect of continuing to run.

Thanks,
Nick

  reply	other threads:[~2022-11-10 11:50 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-28  6:31 [PATCH 00/17] powerpc: alternate queued spinlock implementation Nicholas Piggin
2022-07-28  6:31 ` [PATCH 01/17] powerpc/qspinlock: powerpc qspinlock implementation Nicholas Piggin
2022-08-10  1:52   ` Jordan NIethe
2022-08-10  6:48     ` Christophe Leroy
2022-11-10  0:35   ` Jordan Niethe
2022-11-10  6:37     ` Christophe Leroy
2022-11-10 11:44       ` Nicholas Piggin
2022-11-10  9:09     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 1a/17] powerpc/qspinlock: Prepare qspinlock code Nicholas Piggin
2022-07-28  6:31 ` [PATCH 02/17] powerpc/qspinlock: add mcs queueing for contended waiters Nicholas Piggin
2022-08-10  2:28   ` Jordan NIethe
2022-11-10  0:36   ` Jordan Niethe
2022-11-10  9:21     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 03/17] powerpc/qspinlock: use a half-word store to unlock to avoid larx/stcx Nicholas Piggin
2022-08-10  3:28   ` Jordan Niethe
2022-11-10  0:39   ` Jordan Niethe
2022-11-10  9:25     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 04/17] powerpc/qspinlock: convert atomic operations to assembly Nicholas Piggin
2022-08-10  3:54   ` Jordan Niethe
2022-11-10  0:39   ` Jordan Niethe
2022-11-10  8:36     ` Christophe Leroy
2022-11-10 11:48       ` Nicholas Piggin [this message]
2022-11-10  9:40     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 05/17] powerpc/qspinlock: allow new waiters to steal the lock before queueing Nicholas Piggin
2022-08-10  4:31   ` Jordan Niethe
2022-11-10  0:40   ` Jordan Niethe
2022-11-10 10:54     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 06/17] powerpc/qspinlock: theft prevention to control latency Nicholas Piggin
2022-08-10  5:51   ` Jordan Niethe
2022-11-10  0:40   ` Jordan Niethe
2022-11-10 10:57     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 07/17] powerpc/qspinlock: store owner CPU in lock word Nicholas Piggin
2022-08-12  0:50   ` Jordan Niethe
2022-11-10  0:40   ` Jordan Niethe
2022-11-10 10:59     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 08/17] powerpc/qspinlock: paravirt yield to lock owner Nicholas Piggin
2022-08-12  2:01   ` Jordan Niethe
2022-11-10  0:41   ` Jordan Niethe
2022-11-10 11:13     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 09/17] powerpc/qspinlock: implement option to yield to previous node Nicholas Piggin
2022-08-12  2:07   ` Jordan Niethe
2022-11-10  0:41   ` Jordan Niethe
2022-11-10 11:14     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 10/17] powerpc/qspinlock: allow stealing when head of queue yields Nicholas Piggin
2022-08-12  4:06   ` Jordan Niethe
2022-11-10  0:42   ` Jordan Niethe
2022-11-10 11:22     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 11/17] powerpc/qspinlock: allow propagation of yield CPU down the queue Nicholas Piggin
2022-08-12  4:17   ` Jordan Niethe
2022-10-06 17:27   ` Laurent Dufour
2022-11-10  0:42   ` Jordan Niethe
2022-11-10 11:25     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 12/17] powerpc/qspinlock: add ability to prod new queue head CPU Nicholas Piggin
2022-08-12  4:22   ` Jordan Niethe
2022-11-10  0:42   ` Jordan Niethe
2022-11-10 11:32     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 13/17] powerpc/qspinlock: trylock and initial lock attempt may steal Nicholas Piggin
2022-08-12  4:32   ` Jordan Niethe
2022-11-10  0:43   ` Jordan Niethe
2022-11-10 11:35     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 14/17] powerpc/qspinlock: use spin_begin/end API Nicholas Piggin
2022-08-12  4:36   ` Jordan Niethe
2022-11-10  0:43   ` Jordan Niethe
2022-11-10 11:36     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 15/17] powerpc/qspinlock: reduce remote node steal spins Nicholas Piggin
2022-08-12  4:43   ` Jordan Niethe
2022-11-10  0:43   ` Jordan Niethe
2022-11-10 11:37     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 16/17] powerpc/qspinlock: allow indefinite spinning on a preempted owner Nicholas Piggin
2022-08-12  4:49   ` Jordan Niethe
2022-09-22 15:02   ` Laurent Dufour
2022-09-23  8:16     ` Nicholas Piggin
2022-11-10  0:44   ` Jordan Niethe
2022-11-10 11:38     ` Nicholas Piggin
2022-07-28  6:31 ` [PATCH 17/17] powerpc/qspinlock: provide accounting and options for sleepy locks Nicholas Piggin
2022-08-15  1:11   ` Jordan Niethe
2022-11-10  0:44   ` Jordan Niethe
2022-11-10 11:41     ` Nicholas Piggin

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