Re: [PATCH v2 13/51] IB/qib: Add qib_driver.c

2010-04-07 Thread Roland Dreier 
  +DEFINE_MUTEX(qib_mutex);/* general driver use */

Rather than having this ill-defined mutex that I think is going to make
it hard to understand the locking and get the lock ordering right, would
it be better to have well-defined locking rules?  AFAICT this mutex is
used in only two places, qib_diag.c and qib_file_op.c.  Are those two
uses protecting the same thing?  Or could we have two static mutexes,
one in each file, that protects what each file needs protected?
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Re: [PATCH v2 13/51] IB/qib: Add qib_driver.c

2010-04-07 Thread Steve Wise 

Roland Dreier wrote:

  +unsigned qib_debug;
  +module_param_named(debug, qib_debug, uint, S_IWUSR | S_IRUGO);
  +MODULE_PARM_DESC(debug, mask for debug prints);

Did you look at using trace events for this stuff?  That gives you
extremely low overhead when tracing is turned off (dynamic patching to
NOP out the tracing when it's disabled) and also very fine-grained (per
trace site) control over what gets printed; plus you get dumping of the
trace buffer on crash, etc.

 - R.
  


Where can I find information on trace events?  Something in Documentation/*?

Thanks,


Steve.


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Re: [PATCH v2 13/51] IB/qib: Add qib_driver.c

2010-04-07 Thread John A. Gregor 
Roland Dreier rdre...@cisco.com wrote:
   Where can I find information on trace events?  Something in 
 Documentation/*?

 Yep, Documentation/trace/events.txt.

LWN just did a really good writeup on using the TRACE_EVENT macro:

http://lwn.net/Articles/379903/

Part 2 is still behind the paywall.

-John Gregor
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