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.
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