Re: signalfd API issues (was Re: [PATCH/RFC] signal races/bugs, losing TIF_SIGPENDING and other woes)

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2007-06-06 at 22:20 -0400, Jeff Dike wrote:
> On Thu, Jun 07, 2007 at 08:43:42AM +1000, Paul Mackerras wrote:
> > What Ben was talking about was stealing a synchronous SEGV from a task
> > without stopping it, and as Ben says that makes no sense.
> > Intercepting a signal and stopping the task is reasonable, and that is
> > what ptrace does, and I assume also UML.
> 
> It is, but I can also see UML stealing the SEGV from the child.  The
> UML skas does this - a ptrace extension, PTRACE_FAULTINFO, is used to
> extract page fault information from the child, and other pieces of the
> patch are used to fix the fault without the child continuing until
> it's fixed.  So, in this case, the child never sees the SEGV.

But you use ptrace and don't steal signals with dequeue_signal() on a
live other task, which is ok.

Ben.


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