[compiler-rt] r193519 - tsan: start the background thread with signals blocked, otherwise it can steal users signals

[Reid Kleckner]

Can a signal be delivered to the child during startup?  I've observed this
in DR and it gave me a lot of pain.  Maybe a more robust way to do this
would be to:

1. block signals in parent, save old sigset
2. spawn child thread with signals blocked (I think it uses the parent's
set?)
3. unblock signals in the parent


On Mon, Oct 28, 2013 at 8:29 AM, Dmitry Vyukov <dvyukov at google.com> wrote:

> Author: dvyukov
> Date: Mon Oct 28 07:29:32 2013
> New Revision: 193519
>
> URL: http://llvm.org/viewvc/llvm-project?rev=193519&view=rev
> Log:
> tsan: start the background thread with signals blocked, otherwise it can
> steal users signals
>
>
> Modified:
>     compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc
>
> Modified: compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc?rev=193519&r1=193518&r2=193519&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc (original)
> +++ compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc Mon Oct 28
> 07:29:32 2013
> @@ -2191,9 +2191,15 @@ void InitializeInterceptors() {
>  }
>
>  void internal_start_thread(void(*func)(void *arg), void *arg) {
> +  // Start the thread with signals blocked, otherwise it can steal users
> +  // signals.
> +  __sanitizer_kernel_sigset_t set, old;
> +  internal_sigfillset(&set);
> +  internal_sigprocmask(SIG_SETMASK, &set, &old);
>    void *th;
>    REAL(pthread_create)(&th, 0, (void*(*)(void *arg))func, arg);
>    REAL(pthread_detach)(th);
> +  internal_sigprocmask(SIG_SETMASK, &old, 0);
>  }
>
>  }  // namespace __tsan
>
>
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