[llvm-dev] greendragon build noisy due to mmap_stress.cc

[Dmitry Vyukov via llvm-dev]

On Fri, Jan 22, 2016 at 4:17 PM, Dmitry Vyukov <dvyukov at google.com> wrote:
> On Fri, Jan 22, 2016 at 4:11 PM, Kuba Brecka <jbrecka at apple.com> wrote:
>> Hm, I tried to reproduce this as well, but unsuccessfully.  From the crash
>> report:  EXC_I386_GPFLT means we’re dereferencing a non-canonical pointer,
>> in this case “0x00486000000025df”.  This happens at wrap_OSSpinLockLock+17,
>> which is just after the prologue and just after calling cur_thread().  So
>> I’d say it happens when we’re dereferencing the pointer returned by
>> cur_thread().  On OS X, we’re doing this trick where we store the
>> ThreadState pointer in the shadow memory.  Could it be that something
>> actually read/wrote the memory that is backed by the same place as the
>> shadow memory?
>>
>> Does “0x00486000000025df” like a reasonable content of a shadow cell?
>
>
>
> Yes, it looks like a reasonable shadow:
>
> // Shadow (from most significant bit):
> //   freed           : 1
> //   tid             : kTidBits
> //   is_atomic       : 1
> //   is_read         : 1
> //   size_log        : 2
> //   addr0           : 3
> //   epoch           : kClkBits


+Nico pointed to another failure:
http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA_check/9782/testReport/ThreadSanitizer/ThreadSanitizer/mmap_stress_cc/