Date: Mon, 15 Sep 2014 19:59:50 -0700 From: Matthew Ahrens <mahrens@delphix.com> To: Steven Hartland <smh@freebsd.org> Cc: hackers@freebsd.org, freebsd-dtrace@freebsd.org Subject: Re: ZFS SET_ERROR dtrace probe possible under FreeBSD? Message-ID: <CAJjvXiF4kPFW--SioqAvR%2BF1kwMgYUkfGqtLd4ZHh0jWhrNN5Q@mail.gmail.com> In-Reply-To: <AEC968EBE6DE4E56A76DD7578DC25483@multiplay.co.uk> References: <AEC968EBE6DE4E56A76DD7578DC25483@multiplay.co.uk>
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Disclaimer: I'm not an expert in FreeBSD dtrace. It looks like the FreeBSD kernel uses these declaration for kernel SDT probes, in sdt.h: 333 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#333>#*define* DTRACE_PROBE1 <http://src.illumos.org/source/s?refs=DTRACE_PROBE1&project=freebsd-head>(name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>, type0 <http://src.illumos.org/source/s?defs=type0&project=freebsd-head>, arg0 <http://src.illumos.org/source/s?defs=arg0&project=freebsd-head>) \334 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#334>; DTRACE_PROBE_IMPL_START <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#DTRACE_PROBE_IMPL_START>(name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>, arg0 <http://src.illumos.org/source/s?defs=arg0&project=freebsd-head>, 0, 0, 0, 0) \335 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#335>; SDT_PROBE_ARGTYPE <http://src.illumos.org/source/s?defs=SDT_PROBE_ARGTYPE&project=freebsd-head>(sdt <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#sdt>, , , name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>, 0, #type0 <http://src.illumos.org/source/s?defs=type0&project=freebsd-head>, NULL <http://src.illumos.org/source/s?defs=NULL&project=freebsd-head>); \336 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#336>; DTRACE_PROBE_IMPL_END <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#DTRACE_PROBE_IMPL_END>; 324 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#324>#*define* DTRACE_PROBE_IMPL_START <http://src.illumos.org/source/s?refs=DTRACE_PROBE_IMPL_START&project=freebsd-head>(name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>, arg0 <http://src.illumos.org/source/s?defs=arg0&project=freebsd-head>, arg1 <http://src.illumos.org/source/s?defs=arg1&project=freebsd-head>, arg2 <http://src.illumos.org/source/s?defs=arg2&project=freebsd-head>, arg3 <http://src.illumos.org/source/s?defs=arg3&project=freebsd-head>, arg4 <http://src.illumos.org/source/s?defs=arg4&project=freebsd-head>) *do* { \325 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#325>; *static* SDT_PROBE_DEFINE <http://src.illumos.org/source/s?defs=SDT_PROBE_DEFINE&project=freebsd-head>(sdt <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#sdt>, , , name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>); \326 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#326>; SDT_PROBE <http://src.illumos.org/source/s?defs=SDT_PROBE&project=freebsd-head>(sdt <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#sdt>, , , name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>, arg0 <http://src.illumos.org/source/s?defs=arg0&project=freebsd-head>, arg1 <http://src.illumos.org/source/s?defs=arg1&project=freebsd-head>, arg2 <http://src.illumos.org/source/s?defs=arg2&project=freebsd-head>, arg3 <http://src.illumos.org/source/s?defs=arg3&project=freebsd-head>, arg4 <http://src.illumos.org/source/s?defs=arg4&project=freebsd-head>);327 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#327>#*define* DTRACE_PROBE_IMPL_END <http://src.illumos.org/source/s?refs=DTRACE_PROBE_IMPL_END&project=freebsd-head>; } *while* (0) 163 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#163>#*define* SDT_PROBE <http://src.illumos.org/source/s?refs=SDT_PROBE&project=freebsd-head>(prov <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#prov>, mod <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#mod>, func <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#func>, name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>, arg0 <http://src.illumos.org/source/s?defs=arg0&project=freebsd-head>, arg1 <http://src.illumos.org/source/s?defs=arg1&project=freebsd-head>, arg2 <http://src.illumos.org/source/s?defs=arg2&project=freebsd-head>, arg3 <http://src.illumos.org/source/s?defs=arg3&project=freebsd-head>, arg4 <http://src.illumos.org/source/s?defs=arg4&project=freebsd-head>) *do* { \164 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#164>; *if* (sdt_ <http://src.illumos.org/source/s?defs=sdt_&project=freebsd-head>##prov <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#prov>##_##mod <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#mod>##_##func <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#func>##_##name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>->id <http://src.illumos.org/source/s?defs=id&project=freebsd-head>) \165 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#165>; (*sdt_probe_func <http://src.illumos.org/source/s?defs=sdt_probe_func&project=freebsd-head>)(sdt_ <http://src.illumos.org/source/s?defs=sdt_&project=freebsd-head>##prov <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#prov>##_##mod <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#mod>##_##func <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#func>##_##name <http://src.illumos.org/source/s?defs=name&project=freebsd-head>->id <http://src.illumos.org/source/s?defs=id&project=freebsd-head>, \166 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#166>; (uintptr_t <http://src.illumos.org/source/s?defs=uintptr_t&project=freebsd-head>) arg0 <http://src.illumos.org/source/s?defs=arg0&project=freebsd-head>, (uintptr_t <http://src.illumos.org/source/s?defs=uintptr_t&project=freebsd-head>) arg1 <http://src.illumos.org/source/s?defs=arg1&project=freebsd-head>, (uintptr_t <http://src.illumos.org/source/s?defs=uintptr_t&project=freebsd-head>) arg2 <http://src.illumos.org/source/s?defs=arg2&project=freebsd-head>, \167 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#167>; (uintptr_t <http://src.illumos.org/source/s?defs=uintptr_t&project=freebsd-head>) arg3 <http://src.illumos.org/source/s?defs=arg3&project=freebsd-head>, (uintptr_t <http://src.illumos.org/source/s?defs=uintptr_t&project=freebsd-head>) arg4 <http://src.illumos.org/source/s?defs=arg4&project=freebsd-head>); \168 <http://src.illumos.org/source/xref/freebsd-head/sys/sys/sdt.h#168>} *while* (0) To do the equivalent "extra static" magic, you will need to expand out the DTRACE_PROBE1 macro. I think it should look something like: SDT_PROBE_DEFINE1(sdt, zfs, , set__error, "int"); #define SET_ERROR(err) \ ((sdt_sdt_zfs__set__error->id && \ (*sdt_probe_func)(sdt_sdt_zfs__set__error->id, (uintptr_t)err, 0, 0, 0, 0)), \ err) Note that SET_ERROR is an expansion of SDT_PROBE, but rewritten to be a single statement, so that we can do the same trick with the comma operator. --matt On Mon, Sep 15, 2014 at 7:03 PM, Steven Hartland <smh@freebsd.org> wrote: > The following commit added SET_ERROR dtrace probes to illumos > https://github.com/illumos/illumos-gate/commit/be6fd75 > > Now we have all the SET_ERROR calls but the FreeBSD's ZFS implementation > but our SET_ERROR in sys/cddl/compat/opensolaris/sys/sdt.h is simply: > #define SET_ERROR(err) (err) > > I tried using the illumos version but that resulted being unable > to mount ZFS root, so clearly not right. > > /* > * the set-error SDT probe is extra static, in that we declare its fake > * function literally, rather than with the DTRACE_PROBE1() macro. This is > * necessary so that SET_ERROR() can evaluate to a value, which wouldn't > * be possible if it required multiple statements (to declare the function > * and then call it). > * > * SET_ERROR() uses the comma operator so that it can be used without much > * additional code. For example, "return (EINVAL);" becomes > * "return (SET_ERROR(EINVAL));". Note that the argument will be evaluated > * twice, so it should not have side effects (e.g. something like: > * "return (SET_ERROR(log_error(EINVAL, info)));" would log the error > twice). > */ > extern void __dtrace_probe_set__error(uintptr_t); > #define SET_ERROR(err) (__dtrace_probe_set__error(err), err) > > > For those that know the the ins and outs of our dtrace is it > possible for us to add support for this trace point? > > Regards > Steve > _______________________________________________ > freebsd-dtrace@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-dtrace > To unsubscribe, send any mail to "freebsd-dtrace-unsubscribe@freebsd.org" >
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