From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Andrea Parri <andrea.parri@amarulasolutions.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: zhe.he@windriver.com, catalin.marinas@arm.com,
tglx@linutronix.de, rostedt@goodmis.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
boqun.feng@gmail.com
Subject: Re: [PATCH v2] kmemleak: Turn kmemleak_lock to raw spinlock on RT
Date: Fri, 23 Nov 2018 12:06:11 +0100 [thread overview]
Message-ID: <20181123110611.s2gmd237j7docrxt@linutronix.de> (raw)
In-Reply-To: <20181123110226.GA5125@andrea>
On 2018-11-23 12:02:55 [+0100], Andrea Parri wrote:
> > is this an RT-only problem? Because mainline should not allow read->read
> > locking or read->write locking for reader-writer locks. If this only
> > happens on v4.18 and not on v4.19 then something must have fixed it.
>
> Probably misunderstanding, but I'd say that read->read locking is "the
> norm"...?
>
> If you don't use qrwlock, readers are also "recursive", in part.,
>
> P0 P1
> read_lock(l)
> write_lock(l)
> read_lock(l)
>
> won't block P0 on the second read_lock(). (qrwlock somehow complicate
> the analysis; IIUC, they are recursive if and only if in_interrupt().).
ehm, peterz, is that true? My memory on that is that all readers will
block if there is a writer pending.
> Andrea
Sebastian
next prev parent reply other threads:[~2018-11-23 11:06 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-22 9:04 [PATCH v2] kmemleak: Turn kmemleak_lock to raw spinlock on RT zhe.he
2018-11-22 10:16 ` Sebastian Andrzej Siewior
2018-11-23 9:53 ` Sebastian Andrzej Siewior
2018-11-23 11:02 ` Andrea Parri
2018-11-23 11:06 ` Sebastian Andrzej Siewior [this message]
2018-11-23 11:31 ` Catalin Marinas
2018-11-23 15:51 ` Steven Rostedt
2018-11-26 8:40 ` Peter Zijlstra
2018-11-24 14:26 ` He Zhe
2018-11-30 18:19 ` Sebastian Andrzej Siewior
2018-12-05 13:53 ` He Zhe
2018-12-05 19:14 ` Sebastian Andrzej Siewior
2018-12-18 10:51 ` He Zhe
2018-12-18 15:07 ` Catalin Marinas
2018-12-19 15:30 ` Sebastian Andrzej Siewior
2018-12-20 1:46 ` He Zhe
2018-12-18 15:12 ` Catalin Marinas
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