bug#19676: madvise bug in guile-git

[Linas Vepstas]

Hi,

I've got a test where hit guile with maybe a dozen threads doing
assorted things.   Doing this, I then see handful of these messages:
"madvise failed: Cannot allocate memory" every 5 or 10 seconds.
Except for the printing, everything seems stable.  I've aptured a
stack trace for this, below, by pulling from today's git  (24 January)
and adding an abort right after the print.

The stack trace is not very enlightening (to me).  I figure that
either madvise is freeing something previously freed 9??) or that
there is either a glibc or a kernel bug.

--linas

Details below;


diff --git a/libguile/vm.c b/libguile/vm.c
index 0e59835..4911897 100644
--- a/libguile/vm.c
+++ b/libguile/vm.c
@@ -917,8 +917,17 @@ return_unused_stack_to_os (struct scm_vm *vp)
         ret = madvise ((void *) start, end - start, MADV_DONTNEED);
       while (ret && errno == -EAGAIN);

-      if (ret)
+      if (ret) {
         perror ("madvise failed");
+fprintf(stderr, "duuude start=%lx end=%lx sz=%lu\n", start, end, end -
+start);
+
+
+abort();
+
+
+
+}
     }

   vp->sp_max_since_gc = vp->sp;


All this is on Linux Mint "Rebecca" which is a modified version of
Ubuntu 14.04

Otherer system info:
$ cat /proc/version
Linux version 3.13.0-43-generic (address@hidden) (gcc version 4.8.2
(Ubuntu 4.8.2-19ubuntu1) ) #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC 2014

$ gcc --version
gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2


$ dpkg -S /lib/x86_64-linux-gnu/libc-2.19.so
libc6:amd64: /lib/x86_64-linux-gnu/libc-2.19.so


madvise failed: Cannot allocate memory
duuude start=7f8653535000 end=7f8653536000 sz=4096
[2015-01-24 20:00:34:900] [ERROR] Caught signal 6 (Aborted) on thread
140213737207552
    Stack Trace:
    2: basic_string.h:539    ~basic_string()
    3: CogServerMain.cc:78    _Z7sighandi()
    4: ??:0    killpg()
    5: raise.c:56    __GI_raise()
    6: abort.c:91    __GI_abort()
    7: vm.c:926    return_unused_stack_to_os()
    8: vm.c:1024    scm_i_vm_mark_stack()
    9: ??:0    GC_mark_from()
    10: ??:0    GC_mark_some()
    11: ??:0    GC_stopped_mark()
    12: ??:0    GC_try_to_collect_inner()
    13: ??:0    GC_collect_or_expand()
    14: ??:0    GC_allocobj()
    15: ??:0    GC_generic_malloc_inner()
    16: ??:0    GC_generic_malloc()
    17: ??:0    GC_core_malloc()
    18: gc.h:229    scm_double_cell()
    19: throw.c:364    scm_c_catch()
    20: SchemeEval.cc:527      opencog::SchemeEval::do_eval(std::string const&)
    21: SchemeEval.cc:470      opencog::SchemeEval::c_wrap_eval(void*)
    22: continuations.c:426    c_body()
    23: vm-engine.c:809    vm_regular_engine()
    24: vm.c:1269    scm_call_n()
    25: throw.c:138    catch()
    26: continuations.c:371    scm_i_with_continuation_barrier()
    27: continuations.c:465    scm_c_with_continuation_barrier()
    28: threads.c:789    with_guile_and_parent()
    29: ??:0    GC_call_with_stack_base()
    30: threads.c:837    scm_with_guile()
    31: SchemeEval.cc:438
opencog::SchemeEval::eval_expr(std::string const&)
    32: basic_string.h:293      std::string::_M_data() const
    33: ??:0
std::this_thread::__sleep_for(std::chrono::duration<long,
std::ratio<1l, 1l> >, std::chrono::duration<long, std::ratio<1l,
1000000000l> >)
    34: pthread_create.c:312    start_thread()
    35: clone.S:113    clone()