Re: [PATCH] Notifier for significant events on i386

From: Vamsi Krishna S . (
Date: Thu Dec 12 2002 - 02:34:06 EST

On Thu, Dec 12, 2002 at 12:25:47AM +0000, Stephen Hemminger wrote:
> This patch changes notifier to use RCU. No interface change, just a little
> more memory in each notifier_block. Also some formatting cleanup.
> Please review and give comments.
> <snip patch>

This looks good. I have a few of comments:

- add read_lock_rcu() / read_unlock_rcu() around the loop in
  notifier_call_chain() to be preempt-safe.

- I would suggest using struct list_head in the notifier_block
  and use the RCU list routines from include/linux/list.h
  instead of spreading subtle RCU memory-barrier black magic.

- Even though RCU list reading is lockless, premption needs to
  be disabled while reading as mentioned above. So, we do
  need an __notifier_call_chain() version for those handlers
  that could sleep inside the handler: they will have to
  handle the required locking themselves.

Vamsi Krishna S.
Linux Technology Center,
IBM Software Lab, Bangalore.
Ph: +91 80 5044959
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