Re: [PATCH] ipv4: fix the rcu race between free_fib_info andip_route_output_slow

[David Miller]

From: Yanmin Zhang <yanmin_zhang@xxxxxxxxxxxxxxx>
Date: Wed, 23 May 2012 11:02:03 +0800

> 1) Why does free_fib_info call call_rcu instead of releasing fi directly?
> I assume other cpu might be accessing it. nexthop_nh->nh_dev is in fi.
> If other cpu are accessing it, here resetting to NULL would cause other
> cpu panic.

Because fib trie lookups are done with RCU locking, therefore we must
use RCU freeing to release the object.

What I was trying to impart to you is that removing the NULL
assignment is wrong and that an alternative fix is warranted (hint:
consider moving something into the RCU release).
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/