From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de, Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH RT] crypto: limit more FPU-enabled sections
Date: Thu, 30 Nov 2017 16:41:08 +0100 [thread overview]
Message-ID: <20171130154108.GC11362@linutronix.de> (raw)
In-Reply-To: <20171130102948.22d451cd@gandalf.local.home>
On 2017-11-30 10:29:48 [-0500], Steven Rostedt wrote:
> > +static void camellia_fpu_end_rt(struct crypt_priv *ctx)
> > +{
> > +#if CONFIG_PREEMPT_RT_FULL
> > + bool fpu_enabled = ctx->fpu_enabled;
> > +
> > + if (!fpu_enabled)
> > + return;
> > + camellia_fpu_end(fpu_enabled);
> > + ctx->fpu_enabled = false;
> > +#endif
> > +}
> > +
> > +static void camellia_fpu_sched_rt(struct crypt_priv *ctx)
> > +{
> > +#if CONFIG_PREEMPT_RT_FULL
> > + bool fpu_enabled = ctx->fpu_enabled;
> > +
> > + if (!fpu_enabled || !tif_need_resched_now())
> > + return;
> > + camellia_fpu_end(fpu_enabled);
>
> I haven't looked deeply, but why does this call the camellia_fpu_end()
> but other *_fpu_sched_rt() do not call the equivalent?
There is lrw_encrypt() which as "end" function after the end of the full
operation. So encrypt_callback() might be invoked multiple times but
only the first invocation does the fpu-enable part.
#1 We need to disable-FTP after one invocation of encrypt_callback()
because blkcipher_walk_done() might alloc/free/map memory.
#2 That camellia_fpu_sched_rt() is only RT specific in order to enable
preempt if need-resched is set for a RT task. For !RT we continue.
> > + kernel_fpu_end();
> > + /* schedule due to preemptible */
> > + kernel_fpu_begin();
> > +#endif
> > +}
> > +
>
> These are duplicate functions. Shouldn't they go into a header file?
>
> Also, they are very similar:
That whole thing is kind of ugly, yes. That *_fpu_end_rt() use a struct
crypt_priv but this is defined in each cipher file.
I would keep it for now until we decide if we keep fixing those things
are disable for RT because it is not worth it. As I said, this is only
x86 specific and we have something similar on ARM with NEON.
But I guess the decision here will be postponed until someone posts
numbers with SW and with this workaround and cyclictest with a cycle of
1 - 10 ms.
Sebastian
next prev parent reply other threads:[~2017-11-30 15:41 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 14:22 [PATCH RT] crypto: limit more FPU-enabled sections Sebastian Andrzej Siewior
2017-11-30 14:30 ` Sebastian Andrzej Siewior
2017-12-01 10:43 ` [PATCH RT] arm*: disable NEON in kernel mode Sebastian Andrzej Siewior
2017-12-01 13:45 ` Sebastian Andrzej Siewior
2017-12-01 14:18 ` Mark Rutland
2017-12-01 14:36 ` Sebastian Andrzej Siewior
2017-12-01 15:03 ` Ard Biesheuvel
2017-12-01 17:58 ` Dave Martin
2017-12-01 18:08 ` Russell King - ARM Linux
2017-12-01 18:24 ` Dave Martin
2017-12-01 19:20 ` Ard Biesheuvel
2017-12-04 9:21 ` Sebastian Andrzej Siewior
2017-12-01 17:14 ` Peter Zijlstra
2017-12-01 17:31 ` Russell King - ARM Linux
2017-12-01 17:39 ` Peter Zijlstra
2017-11-30 15:19 ` [PATCH RT] crypto: limit more FPU-enabled sections Steven Rostedt
2017-11-30 15:22 ` Sebastian Andrzej Siewior
2017-12-01 10:44 ` [PATCH RT v2] " Sebastian Andrzej Siewior
2017-12-01 11:32 ` Peter Zijlstra
2017-12-01 13:32 ` Sebastian Andrzej Siewior
2017-12-01 13:44 ` Peter Zijlstra
2017-12-01 13:50 ` Sebastian Andrzej Siewior
2017-12-01 14:03 ` [PATCH RT v3] " Sebastian Andrzej Siewior
2017-11-30 15:29 ` [PATCH RT] " Steven Rostedt
2017-11-30 15:41 ` Sebastian Andrzej Siewior [this message]
2017-11-30 16:18 ` Steven Rostedt
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