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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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