On Thursday August 28, akpm@linux-foundation.org wrote:

quoted text
>

> I'm curious about how this happened.

>

> afaict from reading the code, this:

>

> 	rcu_read_lock();

> 	might_sleep();

> 	rcu_read_unlock();

>

> will warn if CONFIG_PREEMPT_RCU=n but won't warn if

> CONFIG_PREEMPT_RCU=y.  If correct, that's a nasty trap.

>

> Is that what you did?

Uhm..

$ grep PREEMPT /home/src/md-x86-64/.config

CONFIG_PREEMPT_NONE=y

# CONFIG_PREEMPT_VOLUNTARY is not set

# CONFIG_PREEMPT is not set

$ grep DEBUG_SPIN /home/src/md-x86-64/.config

CONFIG_DEBUG_SPINLOCK=y

CONFIG_DEBUG_SPINLOCK_SLEEP=y

$ grep RCU /home/src/md-x86-64/.config

CONFIG_CLASSIC_RCU=y

# CONFIG_RCU_TORTURE_TEST is not set
This definitely doesn't report an error if I put "might_sleep" inside

rcu_read_lock.  I tried to figure out why but got lost.
BTW, I need the following to get current -git to compile.
NeilBrown
Author: NeilBrown

Date:   Tue Aug 19 11:59:37 2008 +1000
    Fix compile error in security
diff --git a/include/linux/security.h b/include/linux/security.h

index 2ee5ecf..0cc23a1 100644

--- a/include/linux/security.h

+++ b/include/linux/security.h

@@ -1757,7 +1757,7 @@ static inline int security_ptrace_may_access(struct task_struct *child,
 static inline int security_ptrace_traceme(struct task_struct *child)

 {

-	return cap_ptrace_traceme(parent);

+	return cap_ptrace_traceme(child);

 }
 static inline int security_capget(struct task_struct *target,
--

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