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    [PATCH] Add pselect/ppoll system call implementation · 9f72949f
    David Woodhouse 提交于
    The following implementation of ppoll() and pselect() system calls
    depends on the architecture providing a TIF_RESTORE_SIGMASK flag in the
    thread_info.
    
    These system calls have to change the signal mask during their
    operation, and signal handlers must be invoked using the new, temporary
    signal mask. The old signal mask must be restored either upon successful
    exit from the system call, or upon returning from the invoked signal
    handler if the system call is interrupted. We can't simply restore the
    original signal mask and return to userspace, since the restored signal
    mask may actually block the signal which interrupted the system call.
    
    The TIF_RESTORE_SIGMASK flag deals with this by causing the syscall exit
    path to trap into do_signal() just as TIF_SIGPENDING does, and by
    causing do_signal() to use the saved signal mask instead of the current
    signal mask when setting up the stack frame for the signal handler -- or
    by causing do_signal() to simply restore the saved signal mask in the
    case where there is no handler to be invoked.
    
    The first patch implements the sys_pselect() and sys_ppoll() system
    calls, which are present only if TIF_RESTORE_SIGMASK is defined. That
    #ifdef should go away in time when all architectures have implemented
    it. The second patch implements TIF_RESTORE_SIGMASK for the PowerPC
    kernel (in the -mm tree), and the third patch then removes the
    arch-specific implementations of sys_rt_sigsuspend() and replaces them
    with generic versions using the same trick.
    
    The fourth and fifth patches, provided by David Howells, implement
    TIF_RESTORE_SIGMASK for FR-V and i386 respectively, and the sixth patch
    adds the syscalls to the i386 syscall table.
    
    This patch:
    
    Add the pselect() and ppoll() system calls, providing core routines usable by
    the original select() and poll() system calls and also the new calls (with
    their semantics w.r.t timeouts).
    Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>
    Cc: Michael Kerrisk <mtk-manpages@gmx.net>
    Signed-off-by: NAndrew Morton <akpm@osdl.org>
    Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
    9f72949f
poll.h 2.3 KB