[PATCH] D20913: [asan] add primitives that allow coroutine implementations

[Philippe Daouadi via llvm-commits]

blastrock marked 10 inline comments as done.
blastrock added a comment.

@dvyukov I wrote that loop to run the tests longer while the signal triggers, and I have found... a deadlock :(

I am not sure how exceptions work, but it seems that there is a mutex that allow only one stack unwinding to occur at the same time... So when the signal triggers while the mutex is locked, the program is completely deadlocked. Here is the stack I got:

  * thread #1: tid = 11670, 0x00007f1dbfa79ccc libpthread.so.0`__lll_lock_wait + 28, name = 'swapcontext_ann', stop reason = signal SIGSTOP
    * frame #0: 0x00007f1dbfa79ccc libpthread.so.0`__lll_lock_wait + 28
      frame #1: 0x00007f1dbfa73b05 libpthread.so.0`__GI___pthread_mutex_lock + 117
      frame #2: 0x00007f1dbede0f3a libgcc_s.so.1`_Unwind_Find_FDE [inlined] __gthread_mutex_lock(__mutex=<unavailable>) + 42 at gthr-default.h:748
      frame #3: 0x00007f1dbede0f22 libgcc_s.so.1`_Unwind_Find_FDE at unwind-dw2-fde.c:1005
      frame #4: 0x00007f1dbede0f22 libgcc_s.so.1`_Unwind_Find_FDE(pc=0x00007f1dbeddf18d, bases=0x00007f1dbfdd08d8) + 18 at unwind-dw2-fde-dip.c:448
      frame #5: 0x00007f1dbeddda76 libgcc_s.so.1`uw_frame_state_for(context=0x00007f1dbfdd0830, fs=0x00007f1dbfdd0680) + 102 at unwind-dw2.c:1241
      frame #6: 0x00007f1dbeddecc0 libgcc_s.so.1`uw_init_context_1(context=0x00007f1dbfdd0830, outer_cfa=0x00007f1dbfdd0be0, outer_ra=0x00007f1dbf77c60c) + 80 at unwind-dw2.c:1562
      frame #7: 0x00007f1dbeddf18e libgcc_s.so.1`_Unwind_RaiseException(exc=0x000060d000039860) + 62 at unwind.inc:88
      frame #8: 0x00007f1dbf77c60c libstdc++.so.6`__cxxabiv1::__cxa_throw(obj=0x000060d000039880, tinfo=0x000000000072abc0, dest=0x0000000000000000)(void *)) + 92 at eh_throw.cc:82
      frame #9: 0x00000000004f9dd2 swapcontext_annotation.cc.tmp`Throw() + 82
      frame #10: 0x00000000004f9dee swapcontext_annotation.cc.tmp`ThrowAndCatch() + 14
      frame #11: 0x00000000004fa469 swapcontext_annotation.cc.tmp`handler(int) + 9
      frame #12: 0x00007f1dbfa7ad30 libpthread.so.0`??? + 1
      frame #13: 0x00007f1dbfa750b3 libpthread.so.0`__pthread_mutex_unlock_usercnt + 3
      frame #14: 0x00007f1dbede1074 libgcc_s.so.1`_Unwind_Find_FDE [inlined] __gthread_mutex_unlock(__mutex=<unavailable>) + 356 at gthr-default.h:778
      frame #15: 0x00007f1dbede1063 libgcc_s.so.1`_Unwind_Find_FDE + 123 at unwind-dw2-fde.c:1039
      frame #16: 0x00007f1dbede0fe8 libgcc_s.so.1`_Unwind_Find_FDE(pc=0x00007f1dbeddf18d, bases=0x00007f1dbfdd13e8) + 216 at unwind-dw2-fde-dip.c:448
      frame #17: 0x00007f1dbeddda76 libgcc_s.so.1`uw_frame_state_for(context=0x00007f1dbfdd1340, fs=0x00007f1dbfdd1190) + 102 at unwind-dw2.c:1241
      frame #18: 0x00007f1dbeddecc0 libgcc_s.so.1`uw_init_context_1(context=0x00007f1dbfdd1340, outer_cfa=0x00007f1dbfdd16f0, outer_ra=0x00007f1dbf77c60c) + 80 at unwind-dw2.c:1562
      frame #19: 0x00007f1dbeddf18e libgcc_s.so.1`_Unwind_RaiseException(exc=0x000060d000039930) + 62 at unwind.inc:88
      frame #20: 0x00007f1dbf77c60c libstdc++.so.6`__cxxabiv1::__cxa_throw(obj=0x000060d000039950, tinfo=0x000000000072abc0, dest=0x0000000000000000)(void *)) + 92 at eh_throw.cc:82
      frame #21: 0x00000000004f9dd2 swapcontext_annotation.cc.tmp`Throw() + 82
      frame #22: 0x00000000004f9dee swapcontext_annotation.cc.tmp`ThrowAndCatch() + 14
      frame #23: 0x00000000004f9fe1 swapcontext_annotation.cc.tmp`Child(int) + 129
      frame #24: 0x00007f1dbea6f0c0 libc.so.6
      frame #25: 0x000000000141d0e0 swapcontext_annotation.cc.tmp
      frame #26: 0x00000000004fa7d9 swapcontext_annotation.cc.tmp`main + 601 at swapcontext_annotation.cc:170 [opt]
      frame #27: 0x00007f1dbea4b610 libc.so.6`__libc_start_main + 240
      frame #28: 0x000000000041b699 swapcontext_annotation.cc.tmp`_start + 41

So I guess throwing exceptions from signal handlers is unsafe in the first place, but I couldn't find anything that says it's a bad thing to do.


http://reviews.llvm.org/D20913