* Andrew Morton (akpm@xxxxxxxxxxxxxxxxxxxx) wrote: > On Fri, 7 Nov 2008 13:00:41 -0500 > Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> wrote: > > > * Andrew Morton (akpm@xxxxxxxxxxxxxxxxxxxx) wrote: > > > On Fri, 07 Nov 2008 17:10:00 +0000 David Howells <dhowells@xxxxxxxxxx> wrote: > > > > > > > > > > > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > I'd expect it to behave in the same way as it would if the function was > > > > > implemented out-of-line. > > > > > > > > > > But it occurs to me that the modrobe-doesnt-work thing would happen if > > > > > the function _is_ inlined anyway, so we won't be doing that. > > > > > > > > > > Whatever. Killing this many puppies because gcc may do something so > > > > > bizarrely wrong isn't justifiable. > > > > > > > > With gcc, you get one instance of the static variable from inside a static > > > > (inline or outofline) function per .o file that invokes it, and these do not > > > > merge even though they're common symbols. I asked around and the opinion > > > > seems to be that this is correct C. I suppose it's the equivalent of cutting > > > > and pasting a function between several files - why should the compiler assume > > > > it's the same function in each? > > > > > > > > > > OK, thanks, I guess that makes sense. For static inline. I wonder if > > > `extern inline' or plain old `inline' should change it. > > > > > > It's one of those things I hope I never need to know about, but perhaps > > > we do somewhere have static storage in an inline. Wouldn't surprise > > > me, and I bet that if we do, it's a bug. > > > > Tracepoints actually use that. > > Referring to include/linux/tracepoint.h:DEFINE_TRACE()? > > It does look a bit fragile. Does every .c file which included > include/trace/block.h get a copy of __tracepoint_block_rq_issue, > whether or not it used that tracepoint? Hopefully not. > No, __tracepoint_block_rq_issue is only instanciated if the static inline function is used. One instance per use. > > It could be changed so they use : > > > > DECLARE_TRACE() (in include/trace/group.h) > > DEFINE_TRACE() (in the appropriate kernel c file) > > trace_somename(); (in the code) > > > > instead. That would actually make more sense and remove the need for > > multiple declarations when the same tracepoint name is used in many > > spots (this is a problem kmemtrace has, it generates a lot of tracepoint > > declarations). > > I'm unsure of the requirements here. Do you _want_ each call to > trace_block_rq_issue() to share some in-memory state? If so then yes, > there's a problem with calls to trace_block_rq_issue() from within > separate compilation units. > > otoh, if all calls to trace_block_rq_issue() are supposed to have > independent state (which seems to be the case) then that could be > addressed by making trace_block_rq_issue() a macro which defines > static storage, as cnt32_to_63() shouldn't have done ;) > They could share the same data, given it *has* to be the same. I'll try to fix this. Mathieu > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
