svn commit: r212076 - head/lib/libthr/thread

[Kostik Belousov]

On Thu, Sep 02, 2010 at 04:34:58PM +0000, David Xu wrote:
> Kostik Belousov wrote:
> >On Wed, Sep 01, 2010 at 02:18:33AM +0000, David Xu wrote:
> >>Author: davidxu
> >>Date: Wed Sep  1 02:18:33 2010
> >>New Revision: 212076
> >>URL: http://svn.freebsd.org/changeset/base/212076
> >>
> >>Log:
> >>  Add signal handler wrapper, the reason to add it becauses there are
> >>  some cases we want to improve:
> >>    1) if a thread signal got a signal while in cancellation point,
> >>       it is possible the TDP_WAKEUP may be eaten by signal handler
> >>       if the handler called some interruptibly system calls.
> >>    2) In signal handler, we want to disable cancellation.
> >>    3) When thread holding some low level locks, it is better to
> >>       disable signal, those code need not to worry reentrancy,
> >>       sigprocmask system call is avoided because it is a bit expensive.
> >>  The signal handler wrapper works in this way:
> >>    1) libthr installs its signal handler if user code invokes sigaction
> >>       to install its handler, the user handler is recorded in internal
> >>       array.
> >>    2) when a signal is delivered, libthr's signal handler is invoke,
> >>       libthr checks if thread holds some low level lock or is in critical
> >>       region, if it is true, the signal is buffered, and all signals are
> >>       masked, once the thread leaves critical region, correct signal
> >>       mask is restored and buffered signal is processed.
> >>    3) before user signal handler is invoked, cancellation is temporarily
> >>       disabled, after user signal handler is returned, cancellation state
> >>       is restored, and pending cancellation is rescheduled.
> >
> >>+static void
> >>+thr_sighandler(int sig, siginfo_t *info, void *_ucp)
> >>+{
> >
> >>+	if ((actp->sa_flags & SA_SIGINFO) != 0)
> >>+		(*(sigfunc))(sig, info, ucp);
> >>+	else {
> >>+		((ohandler)(*sigfunc))(
> >>+			sig, info->si_code, (struct sigcontext *)ucp,
> >>+			info->si_addr, (__sighandler_t *)sigfunc);
> >>+	}
> >
> >I do not think this is very important, but freebsd old-style signal
> >handler fourth argument is usually the faulted %eip value. This is
> >most likely irrelevant for any source that is linked with libthr.so
> >new enough to contain this change.
> 
> Isn't the si_addr in siginfo a fault address ? I remembered I saved
> the fault address in ksiginfo_t which is converted to userland
> siginfo, and fault address should be there. what's wrong here ?
> 
Oops, sorry, I miscalculated the position of the arguments :(.
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