[Bug runtime/18320] New: ring_buffer.exp error: implicit declaration of function '__get_cpu_var'

["mcermak at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=18320

            Bug ID: 18320
           Summary: ring_buffer.exp error: implicit declaration of
                    function '__get_cpu_var'
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: mcermak at redhat dot com

When running ring_buffer.exp I see a regression on f20. The testcase was
passing with kernel-3.18.9-100.fc20, but with 3.19.3-100.fc20 it fails.
Observed on both i686 and x86_64. Compiler version was gcc version 4.8.3
20140911 (Red Hat 4.8.3-7) in both cases. 

Issue also reproducible with  f21's gcc-4.9.2-6.fc21.x86_64 on top of
3.19.4-200.fc21.x86_64.

Issue observed observed comparing stap git commit d71ab77 (where it passed) to
81e4501 (where it failed). But after attempting to bisect sources I believe the
issue is caused by underlying kernel change.

Full logs available at https://url.corp.redhat.com/374766f. The systemtap.log
fragment:

=======
Pass 3: translated to C into
"/tmp/stapfer5fy/stap_c4bab2ce137fbbf37e5213f24e9d05e7_1669_src.c" using
115700virt/40028res/6448shr/33996data kb, in 0usr/0sys/0real ms.
In file included from /usr/share/systemtap/runtime/transport/transport.c:65:0,
                 from /usr/share/systemtap/runtime/linux/print.c:17,
                 from /usr/share/systemtap/runtime/print.c:17,
                 from /usr/share/systemtap/runtime/runtime_context.h:22,
                 from
/tmp/stapfer5fy/stap_c4bab2ce137fbbf37e5213f24e9d05e7_1669_src.c:65:
/usr/share/systemtap/runtime/transport/ring_buffer.c: In function
'_stp_ring_buffer_disable_cpu':
/usr/share/systemtap/runtime/transport/ring_buffer.c:13:2: error: implicit
declaration of function '__get_cpu_var' [-Werror=implicit-function-declaration]
  local_inc(&__get_cpu_var(_stp_cpu_disabled));
  ^
/usr/share/systemtap/runtime/transport/ring_buffer.c:13:12: error: lvalue
required as unary '&' operand
  local_inc(&__get_cpu_var(_stp_cpu_disabled));
            ^
/usr/share/systemtap/runtime/transport/ring_buffer.c: In function
'_stp_ring_buffer_enable_cpu':
/usr/share/systemtap/runtime/transport/ring_buffer.c:18:12: error: lvalue
required as unary '&' operand
  local_dec(&__get_cpu_var(_stp_cpu_disabled));
            ^
In file included from /usr/share/systemtap/runtime/transport/ring_buffer.c:6:0,
                 from /usr/share/systemtap/runtime/transport/transport.c:65,
                 from /usr/share/systemtap/runtime/linux/print.c:17,
                 from /usr/share/systemtap/runtime/print.c:17,
                 from /usr/share/systemtap/runtime/runtime_context.h:22,
                 from
/tmp/stapfer5fy/stap_c4bab2ce137fbbf37e5213f24e9d05e7_1669_src.c:65:
/usr/share/systemtap/runtime/transport/ring_buffer.c: In function
'_stp_ring_buffer_cpu_disabled':
/usr/share/systemtap/runtime/transport/ring_buffer.c:24:23: error: lvalue
required as unary '&' operand
     return local_read(&__get_cpu_var(_stp_cpu_disabled));
                       ^
./arch/x86/include/asm/local.h:15:42: note: in definition of macro 'local_read'
 #define local_read(l) atomic_long_read(&(l)->a)
                                          ^
In file included from /usr/share/systemtap/runtime/transport/transport.c:65:0,
                 from /usr/share/systemtap/runtime/linux/print.c:17,
                 from /usr/share/systemtap/runtime/print.c:17,
                 from /usr/share/systemtap/runtime/runtime_context.h:22,
                 from
/tmp/stapfer5fy/stap_c4bab2ce137fbbf37e5213f24e9d05e7_1669_src.c:65:
/usr/share/systemtap/runtime/transport/ring_buffer.c:25:1: error: control
reaches end of non-void function [-Werror=return-type]
 }
 ^
cc1: all warnings being treated as errors
make[4]: *** [/tmp/stapfer5fy/stap_c4bab2ce137fbbf37e5213f24e9d05e7_1669_src.o]
Error 1
make[3]: *** [_module_/tmp/stapfer5fy] Error 2
WARNING: kbuild exited with status: 2
Pass 4: compiled C into "stap_c4bab2ce137fbbf37e5213f24e9d05e7_1669.ko" in
590usr/380sys/908real ms.
Pass 4: compilation failed.  [man error::pass4]
FAIL: RING_BUFFER startup (eof)
Executing: kill -INT -24225
testcase ./systemtap.printf/ring_buffer.exp completed in 1 seconds
=======

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