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SubjectRe: [PATCH 08/16] dma-debug: add core checking functions
On Sun, Jan 11, 2009 at 12:11:27AM +0100, Ingo Molnar wrote:
>
> * Joerg Roedel <joerg.roedel@amd.com> wrote:
>
> > +#define err_printk(dev, format, arg...) do { \
> > + error_count += 1; \
> > + if (show_all_errors || show_num_errors > 0) { \
> > + WARN(1, "%s %s: " format, \
> > + dev_driver_string(dev), \
> > + dev_name(dev) , ## arg); \
> > + } \
> > + if (!show_all_errors && show_num_errors > 0) \
> > + show_num_errors -= 1; \
>
> Note that the arithmetics here is SMP-unsafe: we only hold the hash bucket
> so if two errors hit at once on two CPUs then the error tracking variables
> can be accessed at once.
>
> I'd suggest a simple global lock for this error case (taken inside the
> hash bucket lock), to be on the safe side.

As I wrote in a previous email, a race here is no big deal. I add a
comment to document it. Or do we want another global lock here?

> Also, please dont use a macro for this - printk details can be passed in
> to helper inlines/functions too.

Hmm, how does this look like? There is not WARN variant which can use
va_args as a parameter. And it is important that the error message is
logged in the warning itself. So the driver developer can see it when a
user reports the warning.

Joerg

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