Messages in this thread |  | | | Date | Mon, 24 Oct 2005 07:52:31 -0500 | | From | Corey Minyard <> | | Subject | Re: [PATCH 1/9] ipmi: use refcount in message handler |
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Paul E. McKenney wrote:
>On Sun, Oct 23, 2005 at 11:42:17PM -0500, Matt Domsch wrote: > > >>On Sun, Oct 23, 2005 at 07:19:32PM -0700, Paul E. McKenney wrote: >> >> >>>My guess is that this read-side critical section can be invoked from and >>>SMI, and that SMIs can occur even if interrupts are disabled. If my guess >>>is wrong, please enlighten me. And feel free to ignore the next few >>>paragraphs in that case, along with a number of my suggested changes, >>>since they all depend critically on my guess being correct. >>> >>> >>Paul, it took me a bit to figure this out too, but Corey uses the TLA >>"SMI" to mean "Systems Management Interface", not "Systems Management >>Interrupt". From Documentation/IPMI.txt: >> >>ipmi_msghandler - This is the central piece of software for the IPMI >>system. It handles all messages, message timing, and responses. The >>IPMI users tie into this, and the IPMI physical interfaces (called >>System Management Interfaces, or SMIs) also tie in here. >> >> >>There are at least 4 basic types of physical hardware interfaces (BT, >>SMIC, KCS, and I2C), which may (or more often, may not) have their own >>hardware interrupt lines, but these are normal interrupts, not >>CPU-magic "systems management interrupts". So I think this isn't a >>problem. >> >> > >OK, thank you for the tutorial on the "other SMI"! > > Yeah, I've really misnamed this, unfortunately. Too many TLAs.
>The comments about turning synchronize_rcu() into synchronize_sched() >and rcu_read_lock() into preempt_disable() do not apply, please ignore. > >However, I still do not understand how using RCU on cmd_rcvrs helps, >given that all of the accesses that I could see were already protected >by cmd_rcvrs_lock. > >Any further enlightenment available? > > The calls in handle_ipmb_get_msg_cmd and handle_lan_get_msg_cmd don't need spinlock protection, just an RCU read lock. Kind of the point of the RCU list. Thanks for spotting this.
Thanks,
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