In order to understand what is happening here, can we have a copy of config.log of both userspace RCU and ltt-control, as well as the output of invocation of configure, and output of make V=1 ?
Thanks, Mathieu ----- Original Message ----- > From: "Ondřej Surý" <[email protected]> > To: "Jon Bernard" <[email protected]> > Cc: "Mathieu Desnoyers" <[email protected]>, "Ondřej Surý" > <[email protected]>, "Michael Jeanson" <[email protected]>, "lttng-dev" > <[email protected]> > Sent: Friday, May 23, 2014 7:10:50 PM > Subject: Re: Debian specific userspace RCU configure override > JFTR I did build the urcu and ltt-control on same machine and urcu build went > ok, but ltt-control failed. So there might be something broken. > Although yes, more generally there could be a problem with difference between > build machines, so --disable flag might be helpful. > O. > -- > Ondřej Surý < [email protected] > > Knot DNS ( https://www.knot-dns.cz/ ) – a high-performance DNS server > On 24. 5. 2014, at 0:21, Jon Bernard < [email protected] > wrote: > > * Mathieu Desnoyers < [email protected] > wrote: > > > > Hi, > > > > > > I recently stumbled on this patch: > > > > > > http://sprunge.us/jYcJ > > > > > > It overrides the generated config.h to ensure the > > > > > > "dmb" instruction is not used. > > > > > > However, the proper checks seems to be in place within > > > > > > configure.ac to automatically detect whether to use dmb > > > > > > or not: > > > > > > # ARM-specific checks > > > > > > AS_IF([test "x$ARCHTYPE" = "xarm"],[ > > > > > > AC_MSG_CHECKING([for dmb instruction]) > > > > > > AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ > > > > > > int main() > > > > > > { > > > > > > asm volatile("dmb":::"memory"); > > > > > > return 0; > > > > > > } > > > > > > ]]) > > > > > > ],[ > > > > > > AC_MSG_RESULT([yes]) > > > > > > AC_DEFINE([CONFIG_RCU_ARM_HAVE_DMB], [1]) > > > > > > ],[ > > > > > > AC_MSG_RESULT([no]) > > > > > > ]) > > > > > > ]) > > > > > > My thinking here is that perhaps inappropriate compiler flags > > > > > > are used when the compiler is invoked from within "configure", > > > > > > which leads it to think that it targets an ARMv7+ with dmb. > > > > > > The Debian "armel" architecture AFAIU needs to target older > > > > > > ARM architectures. > > > > > I also wonder if there are some differences between of the arm build > > > machines. I don't have shell access to the machine on which urcu was > > > built so I cannot check, but perhaps that particular machine has dmb. > > > > It would be much better to fix the compiler flags passed to > > > > > > configure and let urcu autodetection do what it is intended > > > > > > to do rather than override the generated file. > > > > > I'll gather and post the compiler flags used for urcu and we'll see. > > > -- > > > Jon > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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