Hello again! Continuing on the same topic as my previous mail, which you may read here:
http://thread.gmane.org/gmane.lisp.guile.bugs/5340 I modified the program to do a `scm_init_guile ()' before creating any threads. This initializes libgc from the main thread, so all should be well. But then I run into a problem: (gdb) r Starting program: /tmp/many_threads [Thread debugging using libthread_db enabled] 0: create[New Thread 0x7ffff740b700 (LWP 23030)] join Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x7ffff740b700 (LWP 23030)] 0x00007ffff7a09200 in GC_malloc (bytes=16) at thread_local_alloc.c:161 161 GC_FAST_MALLOC_GRANS(result, granules, tiny_fl, DIRECT_GRANULES, (gdb) thr apply all bt Thread 2 (Thread 0x7ffff740b700 (LWP 23030)): #0 0x00007ffff7a09200 in GC_malloc (bytes=16) at thread_local_alloc.c:161 #1 0x00007ffff7d1208e in scm_cell (x=<value optimized out>, y=<value optimized out>) at ../libguile/inline.h:124 #2 scm_cons (x=<value optimized out>, y=<value optimized out>) at pairs.c:77 #3 0x00007ffff7cd05b7 in scm_i_with_continuation_barrier (body=0x7ffff7cd03a0 <c_body>, body_data=0x7ffff740adb0, handler=0x7ffff7cd03c0 <c_handler>, handler_data=0x7ffff740adb0, pre_unwind_handler=<value optimized out>, pre_unwind_handler_data=<value optimized out>) at continuations.c:444 #4 0x00007ffff7cd0690 in scm_c_with_continuation_barrier (func=<value optimized out>, data=<value optimized out>) at continuations.c:491 #5 0x00007ffff7a0982f in GC_call_with_gc_active (fn=0x7ffff7d48740 <with_guile_trampoline>, client_data=0x7ffff740ae20) at pthread_support.c:1127 #6 0x00007ffff7d48aed in with_gc_active (func=0x7ffff7d488e0 <do_thread_exit>, data=0x949600, parent=<value optimized out>) at threads.c:97 #7 scm_i_with_guile_and_parent (func=0x7ffff7d488e0 <do_thread_exit>, data=0x949600, parent=<value optimized out>) at threads.c:826 #8 0x00007ffff7d48bc7 in do_thread_exit_trampoline (sb=<value optimized out>, v=0x949600) at threads.c:549 #9 0x00007ffff7a03525 in GC_call_with_stack_base (fn=<value optimized out>, arg=<value optimized out>) at misc.c:1493 #10 0x00007ffff7d48867 in on_thread_exit (v=0x949600) at threads.c:580 #11 0x0000003fc86077f9 in __nptl_deallocate_tsd (arg=0x7ffff740b700) at pthread_create.c:154 #12 start_thread (arg=0x7ffff740b700) at pthread_create.c:308 #13 0x0000003fc7ee098d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115 Thread 1 (Thread 0x7ffff76ce700 (LWP 23027)): #0 0x0000003fc8607fbd in pthread_join (threadid=140737341601536, thread_return=0x7fffffffe018) at pthread_join.c:89 #1 0x00007ffff7a09e47 in GC_pthread_join (thread=140737341601536, retval=0x7fffffffe018) at pthread_support.c:1219 #2 0x00000000004008e7 in main () at many_threads.c:31 What is happening is that I have registered a pthread_key cleanup handler, and I need to call a Guile function in that handler. But quite possibly, libgc has already torn down this thread. So I trampoline through a GC_call_with_stack_base, then register the current thread. If that returns GC_SUCCESS, later I unregister it. In between there is the scm_i_with_guile_and_parent call you see at frame #7. However as you see, there is unhappiness there. I don't know what exactly is causing the segfault, but here's a disassembly: (gdb) disassemble $pc Dump of assembler code for function GC_malloc: 0x00007ffff7a09180 <+0>: mov %rbx,-0x30(%rsp) 0x00007ffff7a09185 <+5>: mov %r13,-0x18(%rsp) 0x00007ffff7a0918a <+10>: mov %rdi,%rbx 0x00007ffff7a0918d <+13>: mov %rbp,-0x28(%rsp) 0x00007ffff7a09192 <+18>: mov %r12,-0x20(%rsp) 0x00007ffff7a09197 <+23>: mov %r14,-0x10(%rsp) 0x00007ffff7a0919c <+28>: mov %r15,-0x8(%rsp) 0x00007ffff7a091a1 <+33>: sub $0x48,%rsp 0x00007ffff7a091a5 <+37>: mov 0x20a104(%rip),%rax # 0x7ffff7c132b0 0x00007ffff7a091ac <+44>: mov (%rax),%r12d 0x00007ffff7a091af <+47>: data32 lea 0x20a3e9(%rip),%rdi # 0x7ffff7c135a0 0x00007ffff7a091b7 <+55>: data32 data32 callq 0x7ffff79f6da0 <__tls_get_addr@plt> 0x00007ffff7a091bf <+63>: mov (%rax),%r13 0x00007ffff7a091c2 <+66>: test %r13,%r13 0x00007ffff7a091c5 <+69>: je 0x7ffff7a0923f <GC_malloc+191> 0x00007ffff7a091c7 <+71>: add $0xf,%r12d 0x00007ffff7a091cb <+75>: movslq %r12d,%r12 0x00007ffff7a091ce <+78>: lea (%rbx,%r12,1),%r12 0x00007ffff7a091d2 <+82>: shr $0x4,%r12 0x00007ffff7a091d6 <+86>: cmp $0x18,%r12 0x00007ffff7a091da <+90>: ja 0x7ffff7a0923f <GC_malloc+191> 0x00007ffff7a091dc <+92>: lea 0x18(%r12),%r14 0x00007ffff7a091e1 <+97>: mov %r12,%rbp 0x00007ffff7a091e4 <+100>: mov $0x10,%r15d 0x00007ffff7a091ea <+106>: shl $0x4,%rbp 0x00007ffff7a091ee <+110>: mov 0x8(%r13,%r14,8),%rax 0x00007ffff7a091f3 <+115>: lea 0x8(%r13,%r14,8),%rcx 0x00007ffff7a091f8 <+120>: cmp $0x11a,%rax 0x00007ffff7a091fe <+126>: jbe 0x7ffff7a09269 <GC_malloc+233> => 0x00007ffff7a09200 <+128>: mov (%rax),%rdx 0x00007ffff7a09203 <+131>: mov %rdx,0x8(%r13,%r14,8) 0x00007ffff7a09208 <+136>: prefetcht0 (%rdx) 0x00007ffff7a0920b <+139>: movq $0x0,(%rax) 0x00007ffff7a09212 <+146>: mov 0x18(%rsp),%rbx 0x00007ffff7a09217 <+151>: mov 0x20(%rsp),%rbp 0x00007ffff7a0921c <+156>: mov 0x28(%rsp),%r12 0x00007ffff7a09221 <+161>: mov 0x30(%rsp),%r13 0x00007ffff7a09226 <+166>: mov 0x38(%rsp),%r14 0x00007ffff7a0922b <+171>: mov 0x40(%rsp),%r15 0x00007ffff7a09230 <+176>: add $0x48,%rsp 0x00007ffff7a09234 <+180>: retq (gdb) info registers rax 0x1000 4096 rbx 0x10 16 rcx 0x6b1650 7018064 rdx 0x2 2 rsi 0x0 0 rdi 0x6027e0 6301664 rbp 0x10 0x10 rsp 0x7ffff740acc0 0x7ffff740acc0 r8 0x7ffff7d490b0 140737351291056 r9 0x0 0 r10 0x7ffff740aba0 140737341598624 r11 0x7ffff7a097c0 140737347884992 r12 0x1 1 r13 0x6b1580 7017856 r14 0x19 25 r15 0x10 16 rip 0x7ffff7a09200 0x7ffff7a09200 <GC_malloc+128> eflags 0x10212 [ AF IF RF ] cs 0x33 51 ss 0x2b 43 ds 0x0 0 es 0x0 0 fs 0x0 0 gs 0x0 0 This is with current CVS. Regards, Andy -- http://wingolog.org/
