"perf record" if BITS_PER_LONG != 64 && !defined(HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT)

[Alexey Brodkin <Alexey.Brodkin@synopsys.com>]

Hi Adrian,

Just noticed that starting from Linux v4.2-rc1 "perf record"
doesn't work on ARC. That's what I see:
 ------------>8------------
 # perf record ls -la
 Cannot use AUX area tracing mmaps
 failed to mmap with 38 (Function not implemented)
 ------------>8------------

I believe that happens because by default auxtrace is enabled
(NO_AUXTRACE=0) and so auxtrace_mmap__mmap() from
"tools/perf/util/auxtrace.c" gets compiled in and following
check fails:
 ------------>8------------
 #if BITS_PER_LONG != 64 && !defined(HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT)
 	pr_err("Cannot use AUX area tracing mmaps\n");
 	return -1;
 #endif
 ------------>8------------

Unfortunately we don't have __sync_val_compare_and_swap()
in our current toolchain. And ARC as of today is 32-bit architecture.

Now if I pass NO_AUXTRACE=1 in perf building command then everything
works as expected.

So I'm wondering what would be the best way to get perf properly
working for ARC (at least) and probably other architecture/toolchain
combos?

I see at least 2 options:

 [1] Add feature check for BITS_PER_LONG. And then if
     "BITS_PER_LONG != 32 & HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT"
     automatically set "NO_AUXTRACE=1" on building perf.

 [2] By default enable auxtrace only on selected architectures.
     For example Intel 64-bit and maybe others who really capable of
     running auxtrace (and may make use of it).

Any suggestions are much appreciated.

Just in case that's my back-trace to auxtrace_mmap__mmap():
 ------------>8------------
#0  auxtrace_mmap__mmap (mm=0x11a1a44, mp=0x5fa468c0, userpg=0x2021e000, fd=4)
    at util/auxtrace.c:57
#1  0x0005d3b0 in __perf_evlist__mmap (evlist=0x11a0f30, evlist=0x11a0f30, 
    fd=4, mp=0x5fa468b8, idx=0) at util/evlist.c:838
#2  perf_evlist__mmap_per_evsel (evlist=evlist@entry=0x11a0f30, 
    idx=idx@entry=0, mp=mp@entry=0x5fa468b8, cpu=cpu@entry=0, 
    thread=thread@entry=0, output=output@entry=0x5fa468b4) at util/evlist.c:861
#3  0x0005de1e in perf_evlist__mmap_per_cpu (mp=0x5fa468b8, evlist=0x11a0f30)
    at util/evlist.c:910
#4  perf_evlist__mmap_ex (evlist=0x11a0f30, evlist@entry=0x0, 
    pages=<optimized out>, overwrite=overwrite@entry=false, auxtrace_pages=0, 
    auxtrace_overwrite=<optimized out>) at util/evlist.c:1095
#5  0x0001e906 in record__open (rec=0xf11a0 <record>) at builtin-record.c:305
#6  __cmd_record (rec=0xf11a0 <record>, argv=<optimized out>, 
    argc=<optimized out>) at builtin-record.c:519
#7  cmd_record (argc=<optimized out>, argv=<optimized out>, 
    prefix=<optimized out>) at builtin-record.c:1168
#8  0x00053758 in run_builtin (p=p@entry=0xf2938 <commands+72>, 
    argc=argc@entry=2, argv=argv@entry=0x11a1730) at perf.c:370
#9  0x00053f10 in handle_internal_command (argv=0x11a1730, argc=2)
    at perf.c:429
#10 run_argv (argv=0x5fa47c70, argcp=0x5fa47c74) at perf.c:473
#11 main (argc=2, argv=0x5fa47d98) at perf.c:588
 ------------>8------------

-Alexey