linux-kernel - Re: How to check whether executing in atomic context?

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Message-ID: <f22d86810910140221q7e03e693kad122a37461cea1d@mail.gmail.com>
Date:	Wed, 14 Oct 2009 02:21:22 -0700
From:	"Leonidas ." <leonidas137@...il.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: How to check whether executing in atomic context?

On Tue, Oct 13, 2009 at 11:36 PM, Leonidas . <leonidas137@...il.com> wrote:
> Hi List,
>
> I am working on a profiler kind of module, the exported apis of my
> module can be
> called from process context and interrupt context as well. Depending on the
> context I am called in, I need to call sleepable/nonsleepable variants
> of my internal
> bookkeeping functions.
>
> I am aware of in_interrupt() call which can be used to check current
> context and take action
> accordingly.
>
> Is there any api which can help figure out whether we are executing
> while hold a spinlock? I.e
> an api which can help figure out sleepable/nonsleepable context? If it
> is not there, what can
> be done for writing the same? Any pointers will be helpful.
>
> -Leo.
>

  While searching through the sources, I found this,

  97/*
  98 * Are we running in atomic context?  WARNING: this macro cannot
  99 * always detect atomic context; in particular, it cannot know about
 100 * held spinlocks in non-preemptible kernels.  Thus it should not be
 101 * used in the general case to determine whether sleeping is possible.
 102 * Do not use in_atomic() in driver code.
 103 */
 104#define in_atomic()     ((preempt_count() & ~PREEMPT_ACTIVE) !=
PREEMPT_INATOMIC_BASE)
 105

this just complicates the matter, right? This does not work in general
case but I think this
will always work if the kernel is preemptible.

Is there no way to write a generic macro?

-Leo.
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