Re: 2.6.27-rc4: lots of 'in_atomic():1, irqs_disabled():0' with software-raid1

[Neil Brown]

On Thursday August 28, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
> 
> 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 <neilb@xxxxxxx>
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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