Re: [GIT PULL] RCU changes for v3.4

[Linus Torvalds]

On Fri, Mar 23, 2012 at 6:47 PM, Paul E. McKenney
<paulmck@xxxxxxxxxxxxxxxxxx> wrote:
>
> This is what I get on a 32-bit build, according to objdump:
>
>        24e3:       64 ff 05 00 00 00 00    incl   %fs:0x0

You do? I'm surprised:

> +static inline void __rcu_read_lock(void)
> +{
> +       __raw_get_cpu_var(rcu_read_lock_nesting)++;
> +       barrier(); /* Keep code within RCU read-side critical section. */
> +}

This looks wrong.

It should use "this_cpu_inc(rcu_read_lock_nesting)", I don't even see
how you get gcc to generate that "inc %fs:" without it.

In general, I don't think you should ever use the __raw_get_cpu_var() things.

                      Linus
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