From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [patch] drivers/zram: Don't disable preemption in zcomp_stream_get/put()
Date: Mon, 17 Oct 2016 18:19:00 +0200 [thread overview]
Message-ID: <1476721140.30636.10.camel@gmail.com> (raw)
In-Reply-To: <20161017142428.25dyxefk2arjeyfz@linutronix.de>
On Mon, 2016-10-17 at 16:24 +0200, Sebastian Andrzej Siewior wrote:
> On 2016-10-16 05:14:22 [+0200], Mike Galbraith wrote:
> >
> > In v4.7, the driver switched to percpu compression streams, disabling
> > preemption (get/put_cpu_ptr()). Use get/put_cpu_light() instead.
>
> I am not convinced that this will work. Nothing prevents
> zram_bvec_write() to be reentrant on the same CPU what I can tell from
> browsing over the code and since it uses zstrm->buffer for compression
> it can go wrong. Also I don't know if crypto's tfm handler can be used
> in parallel for any ops (it usually does not work for crypto).
>
> I suggest a local lock or a good reason why the this patch works.
I used a local lock first, but lockdep was unhappy with it. Ok, back
to the drawing board. Seems to work, but...
-Mike
next prev parent reply other threads:[~2016-10-17 16:19 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-06 8:52 [ANNOUNCE] 4.8-rt1 Sebastian Andrzej Siewior
2016-10-16 3:08 ` [patch] ftrace: Fix latency trace header alignment Mike Galbraith
2016-10-17 13:23 ` Sebastian Andrzej Siewior
2016-10-16 3:11 ` [patch] drivers,connector: Protect send_msg() with a local lock for RT Mike Galbraith
2016-10-17 14:16 ` Sebastian Andrzej Siewior
2016-10-16 3:14 ` [patch] drivers/zram: Don't disable preemption in zcomp_stream_get/put() Mike Galbraith
2016-10-17 14:24 ` Sebastian Andrzej Siewior
2016-10-17 16:19 ` Mike Galbraith [this message]
2016-10-17 16:29 ` Sebastian Andrzej Siewior
2016-10-17 17:18 ` Mike Galbraith
2016-10-17 17:46 ` Mike Galbraith
2016-10-19 15:56 ` [patch v2] " Mike Galbraith
2016-10-19 16:54 ` Sebastian Andrzej Siewior
2016-10-20 2:59 ` Mike Galbraith
2016-10-20 11:02 ` Sebastian Andrzej Siewior
2016-10-16 3:18 ` [patch ]mm/zs_malloc: Fix bit spinlock replacement Mike Galbraith
2016-10-17 15:15 ` Sebastian Andrzej Siewior
2016-10-17 16:12 ` Mike Galbraith
2016-10-17 16:12 ` Mike Galbraith
2016-10-19 15:50 ` [patch v2 ] mm/zs_malloc: " Mike Galbraith
2016-10-20 10:59 ` Sebastian Andrzej Siewior
2016-10-20 9:34 ` [rfc patch] hotplug: Call mmdrop_delayed() in sched_cpu_dying() if PREEMPT_RT_FULL Mike Galbraith
2016-10-20 11:21 ` Sebastian Andrzej Siewior
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