From: David Laight <David.Laight@ACULAB.COM>
To: 'Peter Zijlstra' <peterz@infradead.org>,
Hernan Ponce de Leon <hernan.poncedeleon@huaweicloud.com>
Cc: "mingo@redhat.com" <mingo@redhat.com>,
"will@kernel.org" <will@kernel.org>,
"longman@redhat.com" <longman@redhat.com>,
"boqun.feng@gmail.com" <boqun.feng@gmail.com>,
"akpm@osdl.org" <akpm@osdl.org>,
"arjan@linux.intel.com" <arjan@linux.intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"joel@joelfernandes.org" <joel@joelfernandes.org>,
"paulmck@kernel.org" <paulmck@kernel.org>,
"stern@rowland.harvard.edu" <stern@rowland.harvard.edu>,
"diogo.behrens@huawei.com" <diogo.behrens@huawei.com>,
"jonas.oberhauser@huawei.com" <jonas.oberhauser@huawei.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Hernan Ponce de Leon" <hernanl.leon@huawei.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH] Fix data race in mark_rt_mutex_waiters
Date: Fri, 20 Jan 2023 16:58:20 +0000 [thread overview]
Message-ID: <dc361d8a262b4872acf750f7c8935a28@AcuMS.aculab.com> (raw)
In-Reply-To: <Y8q/5hgXrvOp6vku@hirez.programming.kicks-ass.net>
From: Peter Zijlstra
> Sent: 20 January 2023 16:23
...
> > do {
> > - owner = *p;
> > + owner = READ_ONCE(*p);
> > } while (cmpxchg_relaxed(p, owner,
> > owner | RT_MUTEX_HAS_WAITERS) != owner);
> >
>
> Can't we replace the whole of that function with:
>
> set_bit(0, (unsigned long *)&lock->owner);
>
> ?
If you need the cast then probably not...
There really ought to be a compile-time test (somehow)
that set_bit() is only used on large bit arrays.
OTOH atomic_or32/64() and atomic_and32/64() might use
usable in many places.
On x86 I doubt it makes much difference whether you use
'bis' or 'lock or'.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2023-01-20 16:58 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-20 13:55 Hernan Ponce de Leon
2023-01-20 14:58 ` Arjan van de Ven
2023-01-20 15:54 ` Paul E. McKenney
2023-01-22 15:24 ` Hernan Ponce de Leon
2023-01-23 16:40 ` Paul E. McKenney
2023-01-23 17:34 ` Alan Stern
2023-01-23 17:48 ` Paul E. McKenney
2023-01-23 20:02 ` Jonas Oberhauser
2023-01-24 14:57 ` Hernan Ponce de Leon
2023-01-24 15:42 ` Waiman Long
2023-01-24 15:52 ` Peter Zijlstra
2023-01-24 16:04 ` Waiman Long
2023-01-26 9:42 ` Hernan Ponce de Leon
2023-01-26 12:20 ` Peter Zijlstra
2023-01-26 14:20 ` Peter Zijlstra
2023-01-26 21:07 ` Hernan Ponce de Leon
2023-01-26 22:10 ` David Laight
2023-01-27 1:46 ` Waiman Long
2023-03-01 16:32 ` lock_torture results for different patches: Antonio Paolillo
2023-03-06 7:58 ` Hernan Ponce de Leon
2023-03-10 17:11 ` Paul E. McKenney
2023-01-24 16:12 ` [PATCH] Fix data race in mark_rt_mutex_waiters Paul E. McKenney
2023-01-20 16:23 ` Peter Zijlstra
2023-01-20 16:58 ` David Laight [this message]
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