Re: [Qemu-devel] [PATCH RFC 2/2] tests/tcg: target/s390: Add test for VECTOR LOAD GR FROM VR ELEMENT

[Richard Henderson]

On 2/27/19 11:37 AM, David Hildenbrand wrote:
> #define CHECK_SIGILL(STATEMENT)                  \
> do {                                             \
>     if (signal(SIGILL, sig_sigill) == SIG_ERR) { \
>         check("SIGILL not registered", false);   \
>     }                                            \
>     if (setjmp(jmp_env) == 0) {                  \
>         STATEMENT;                               \
>         check("SIGILL not triggered", false);    \
>     }                                            \
>     if (signal(SIGILL, SIG_DFL) == SIG_ERR) {    \
>         check("SIGILL not registered", false);   \
>     }                                            \
> } while (0)
> 
> 
> However it only works once. During the second signal, QEMU decides to
> set the default handler.
> 
> 1. In a signal handler that signal is blocked. We leave that handler via
> a longjump. So after the first signal, the signal is blocked.

And this is why we use sigaction not signal.

You can set action.sa_flags |= SA_RESETHAND to avoid needing the explicit reset
(or leave it clear to avoid the reset action that you are seeing).

You can set action.sa_flags |= SA_NODEFER to avoid having the signal added to
the signal mask of the thread, to avoid neeing to use sigsetjmp/siglongjmp.  Or
you can just use sigsetjmp/siglongjmp.  ;-)


r~