• Peter Maydell's avatar
    Replace all setjmp()/longjmp() with sigsetjmp()/siglongjmp() · 6ab7e546
    Peter Maydell authored
    The setjmp() function doesn't specify whether signal masks are saved and
    restored; on Linux they are not, but on BSD (including MacOSX) they are.
    We want to have consistent behaviour across platforms, so we should
    always use "don't save/restore signal mask" (this is also generally
    going to be faster). This also works around a bug in MacOSX where the
    signal-restoration on longjmp() affects the signal mask for a completely
    different thread, not just the mask for the thread which did the longjmp.
    The most visible effect of this was that ctrl-C was ignored on MacOSX
    because the CPU thread did a longjmp which resulted in its signal mask
    being applied to every thread, so that all threads had SIGINT and SIGTERM
    blocked.
    
    The POSIX-sanctioned portable way to do a jump without affecting signal
    masks is to siglongjmp() to a sigjmp_buf which was created by calling
    sigsetjmp() with a zero savemask parameter, so change all uses of
    setjmp()/longjmp() accordingly. [Technically POSIX allows sigsetjmp(buf, 0)
    to save the signal mask; however the following siglongjmp() must not
    restore the signal mask, so the pair can be effectively considered as
    "sigjmp/longjmp which don't touch the mask".]
    
    For Windows we provide a trivial sigsetjmp/siglongjmp in terms of
    setjmp/longjmp -- this is OK because no user will ever pass a non-zero
    savemask.
    
    The setjmp() uses in tests/tcg/test-i386.c and tests/tcg/linux-test.c
    are left untouched because these are self-contained singlethreaded
    test programs intended to be run under QEMU's Linux emulation, so they
    have neither the portability nor the multithreading issues to deal with.
    Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
    Reviewed-by: default avatarRichard Henderson <rth@twiddle.net>
    Tested-by: default avatarStefan Weil <sw@weilnetz.de>
    Reviewed-by: default avatarLaszlo Ersek <lersek@redhat.com>
    Signed-off-by: default avatarBlue Swirl <blauwirbel@gmail.com>
    6ab7e546
i386.c 159 KB