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Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep
From: Steven Rostedt <rostedt@goodmis.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Date: Sun, 19 May 2013 12:06:19 -0400
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Cc: linux-m32r-ja@ml.linux-m32r.org, kvm@vger.kernel.org,
 Peter Zijlstra <peterz@infradead.org>,
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On Sun, 2013-05-19 at 16:34 +0300, Michael S. Tsirkin wrote:

> Right but we need to keep it working on upstream as well.
> If I do preempt_enable under a spinlock upstream won't it
> try to sleep under spinlock?

No it wont. A spinlock calls preempt_disable implicitly, and a
preempt_enable() will not schedule unless preempt_count is zero, which
it wont be under a spinlock.

If it did, there would be lots of bugs all over the place because this
is done throughout the kernel (a preempt_enable() under a spinlock).

In other words, don't ever use preempt_enable_no_resched().

-- Steve