Messages in this thread | | | Subject | Re: [PATCH v3 04/23] linux/net.h: use unique identifier for each struct _ddebug | From | Rasmus Villemoes <> | Date | Sat, 10 Nov 2018 00:31:47 +0100 |
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On 10/11/2018 00.22, Joe Perches wrote: > On Sat, 2018-11-10 at 00:10 +0100, Rasmus Villemoes wrote: >> Changes on x86-64 later in this series require that all struct _ddebug >> descriptors in a translation unit uses distinct identifiers. Realize >> that for net_dbg_ratelimited by generating such an identifier via >> __UNIQUE_ID and pass that to an extra level of macros. >> >> No functional change. > > Why does this require an extra indirection _<macro>? >
Because the identifier used in the
>> DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);
line must be the same as the one in the
>> if (DYNAMIC_DEBUG_BRANCH(descriptor) &&
line. That identifier used to be simply "descriptor", with C scope rules making that ok. But because of the asm games I'm playing later, I need to generate a fresh identifier for each instance. That identifier must be referenced in two places in the C source - hence the need to use an extra level of macros to have the __UNIQUE_ID() expanded before _net_dbg_ratelimited gets expanded.
More or less every use of __UNIQUE_ID requires such an extra level (because one very rarely needs to use an identifier exactly once - the point of giving stuff a name is to refer to it again.)
Rasmus
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