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> You said that there were a lot of "stepi" commands to get through
> rcu_read_lock() on x86_64. This is quite surprising, especially if you
> built with CONFIG_RCU_TREE. Even if you built with CONFIG_PREEMPT_RCU_TREE,
> you should only see something like the following from rcu_read_lock():
>
> 000000b7 <__rcu_read_lock>:
> b7: 55 push %ebp
> b8: 64 a1 00 00 00 00 mov %fs:0x0,%eax
> be: ff 80 80 01 00 00 incl 0x180(%eax)
> c4: 89 e5 mov %esp,%ebp
> c6: 5d pop %ebp
> c7: c3 ret
>
> Unless you have some sort of debugging options turned on. Or unless
> six instructions counts for "quite many" stepi commands. ;-)
>
Paul, this should be inlined, dont you think ?
Also, I dont understand why we use ACCESS_ONCE() in rcu_read_lock()
ACCESS_ONCE(current->rcu_read_lock_nesting)++;
Apparently, some compilers are a bit noisy here.
mov 0x1b0(%rdx),%eax
inc %eax
mov %eax,0x1b0(%rdx)
instead of :
incl 0x1b0(%rax)
So if the ACCESS_ONCE() is needed, we might add a comment, because it's
not obvious ;)
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