Re: use of preempt_count instead of in_atomic() at leds-gpio.c

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To: Andrew Morton <akpm@...>
Cc: <stern@...>, <khali@...>, <mb@...>, <hmh@...>, <david-b@...>, <rpurdie@...>, <linux-kernel@...>, <mingo@...>, <geert@...>
Date: Monday, March 24, 2008 - 3:53 pm

Andrew Morton <akpm@linux-foundation.org> wrote:


But then...why would anybody have a reason to read the upcoming LWN
article on the subject?  

OK, how's this?

jon

--

Discourage people from inappropriately using in_atomic()

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 4982998..63a7782 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -72,6 +72,13 @@
 #define in_softirq()		(softirq_count())
 #define in_interrupt()		(irq_count())
 
+/*
+ * Are we running in atomic context?  WARNING: this macro cannot
+ * always detect atomic context; in particular, it cannot know about
+ * held spinlocks in non-preemptible kernels.  Thus it should not be
+ * used in the general case to determine whether sleeping is possible.
+ * Do not use in_atomic() in driver code.
+ */
 #define in_atomic()		((preempt_count() & ~PREEMPT_ACTIVE) != 0)
 
 #ifdef CONFIG_PREEMPT
--
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Messages in current thread:
use of preempt_count instead of in_atomic() at leds-gpio.c, Henrique de Moraes Holschuh..., (Sun Mar 16, 2:43 pm)
Re: use of preempt_count instead of in_atomic() at leds-gpio.c, Henrique de Moraes Holschuh..., (Thu Mar 20, 6:56 pm)
Re: use of preempt_count instead of in_atomic() at leds-gpio.c, Henrique de Moraes Holschuh..., (Thu Mar 20, 10:10 pm)
Re: use of preempt_count instead of in_atomic() at leds-gpio.c, Henrique de Moraes Holschuh..., (Thu Mar 20, 8:36 pm)
Re: use of preempt_count instead of in_atomic() at leds-gpio.c, Henrique de Moraes Holschuh..., (Fri Mar 21, 8:37 am)
Re: use of preempt_count instead of in_atomic() at leds-gpio..., Jonathan Corbet, (Mon Mar 24, 3:53 pm)
Re: use of preempt_count instead of in_atomic() at leds-gpio.c, Henrique de Moraes Holschuh..., (Wed Mar 26, 12:17 pm)