Hello Paul,
On Sun, 26 Jun 2005, Paul E. McKenney wrote:
> How does the following look for NMI-RCU documentation?
That looks good, there is just one bit i'm not entirely sure about and i'd
appreciate it if you could entertain me for a bit;
Answer to Quick Quiz
Why might the rcu_dereference() be necessary on Alpha, given
that the code reference by the pointer is read-only?
Answer: The caller to set_nmi_callback() might well have
initialized some data that is to be used by the
new NMI handler. In this case, the rcu_dereference()
would be needed, because otherwise a CPU that received
an NMI just after the new handler was set might see
the pointer to the new NMI handler, but the old
pre-initialized version of the handler's data.
Reading that i would think the general programming model for this would
be;
setup data
write barrier
setup callback
Isn't that still required considering the following scenario;
CPU0 CPU1
setup data <NMI>
setup callback ...
... call callback
on i386, interrupts are data synchronising events, however if we happen to
take an interrupt right when the data is being setup we won't synchronise
with respect to that data. This could be achieved via the explicit write
barrier after data setup or rcu_dereference in the NMI handler. Or perhaps
i'm missing something?
Thanks!
Zwane
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
