Re: [PATCH -v2 2/3] ACPI, APEI, Add APEI generic error status print support

Huang Ying
2010-11-30T03:29:16Z

On Tue, 2010-11-30 at 11:03 +0800, Andrew Morton wrote:
> On Tue, 30 Nov 2010 10:51:40 +0800 Huang Ying <ying.huang@intel.com> wrote:
>
> > printk is one of the methods to report hardware errors to user space.
> > Hardware error information reported by firmware to Linux kernel is in
> > the format of APEI generic error status (struct
> > acpi_hes_generic_status). This patch adds print support for the
> > format, so that the corresponding hardware error information can be
> > reported to user space via printk.
> >
> > PCIe AER information print is not implemented yet. Will refactor the
> > original PCIe AER information printing code to avoid code duplicating.
> >
> > ...
> >
> > +#define pr_pfx(pfx, fmt, ...) \
> > + printk("%s" fmt, pfx, ##__VA_ARGS__)
>
> hm, why does so much code create little printk helper macros. Isn't
> there something generic somewhere?

Sorry, I do not find the generic code for this helper. But I think this
macro may be helpful for others too, who need to determine the log level
only at runtime. Here corrected errors should have log level:
KERN_WARNING, while uncorrected errors should have log level: KERN_ERR.

Do you think it is a good idea to make this macro generic?

> > /*
> > * CPER record ID need to be unique even after reboot, because record
> > * ID is used as index for ERST storage, while CPER records from
> > @@ -46,6 +49,302 @@ u64 cper_next_record_id(void)
> > }
> > EXPORT_SYMBOL_GPL(cper_next_record_id);
> >
> > +static const char *cper_severity_strs[] = {
> > + [CPER_SEV_RECOVERABLE] = "recoverable",
> > + [CPER_SEV_FATAL] = "fatal",
> > + [CPER_SEV_CORRECTED] = "corrected",
> > + [CPER_SEV_INFORMATIONAL] = "info",
> > +};
> > +
> > +static const char *cper_severity_str(unsigned int severity)
> > +{
> > + return severity < ARRAY_SIZE(cper_severity_strs) ?
> > + cper_severity_strs[severity] : "unknown";
> > +}
>
> This code will explode nastily if CPER_SEV_RECOVERABLE ..
> CPER_SEV_INFORMATIONAL do not exactly have the values 0, 1, 2 and 3.
> They do have those values, but it would be a bit safer if they were
> enumerated types and not #defines..

OK. I will change this.

> > +static void cper_print_bits(const char *pfx, unsigned int bits,
> > + const char *strs[], unsigned int strs_size)
> > +{
> > + int i, len = 0;
> > + const char *str;
> > +
> > + for (i = 0; i < strs_size; i++) {
> > + if (!(bits & (1U << i)))
> > + continue;
> > + str = strs[i];
> > + if (len && len + strlen(str) + 2 > 80) {
> > + printk("\n");
> > + len = 0;
> > + }
> > + if (!len)
> > + len = pr_pfx(pfx, "%s", str);
> > + else
> > + len += printk(", %s", str);
> > + }
> > + if (len)
> > + printk("\n");
> > +}
>
> geeze, that's the sort of code you have to execute to find out what it
> does. Or ask the author to document it.

OK. I will add comments for all necessary functions in the patch.

> This patchset appears to implement a new kernel->userspace interface.
> But that interface isn't actually described anywhere, so reviewers must
> reverse-engineer the interface from the implementation to be able to
> review the interface. Nobody bothers doing that so we end up with an
> unreviewed interface, which we must maintain for eternity.
>
> Please fully document all proposed interfaces?

Sorry. I don't realize that printk-ing something means implementing a
new kernel->userspace interface. I think the messages resulted are
self-explaining for human. Is it sufficient just to add example messages
in patch description?

Best Regards,
Huang Ying