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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