From: "Paul E. McKenney" <paulmck@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
cl@linux.com, penberg@kernel.org, rientjes@google.com,
iamjoonsoo.kim@lge.com, hannes@cmpxchg.org, urezki@gmail.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: Raw spinlocks and memory allocation
Date: Fri, 31 Jul 2020 17:02:23 -0700 [thread overview]
Message-ID: <20200801000223.GU9247@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200731224738.GU23808@casper.infradead.org>
On Fri, Jul 31, 2020 at 11:47:38PM +0100, Matthew Wilcox wrote:
> On Fri, Jul 31, 2020 at 03:30:16PM -0700, Paul E. McKenney wrote:
> > On Fri, Jul 31, 2020 at 02:29:19PM -0700, Andrew Morton wrote:
> > > On Fri, 31 Jul 2020 14:24:57 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > >
> > > > The reason for this restriction is that in -rt, the spin_lock(&zone->lock)
> > > > in rmqueue_bulk() can sleep.
> > >
> > > So if there is runtime overhead, this overhead could be restricted to
> > > -rt kernels with suitable ifdefs?
> >
> > In theory, yes. In practice, with CONFIG_PROVE_RAW_LOCK_NESTING=y,
> > lockdep will complain regardless of -rt or not.
>
> On non-RT, we could make that lock a raw spinlock. On RT, we could
> decline to take the lock. We'd need to abstract the spin_lock() away
> behind zone_lock(zone), but that should be OK.
>
> But let's see if we need to do that.
Fair enough!
Thanx, Paul
prev parent reply other threads:[~2020-08-01 0:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 23:12 Raw spinlocks and memory allocation Paul E. McKenney
2020-07-31 20:38 ` Andrew Morton
2020-07-31 20:48 ` Paul E. McKenney
2020-07-31 20:59 ` Matthew Wilcox
2020-07-31 21:24 ` Paul E. McKenney
2020-07-31 21:29 ` Andrew Morton
2020-07-31 22:30 ` Paul E. McKenney
2020-07-31 22:47 ` Matthew Wilcox
2020-08-01 0:02 ` Paul E. McKenney [this message]
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