On Thu, Sep 02, 2010 at 05:03:13PM +0000, David Xu wrote: > Kostik Belousov wrote: > >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 :(. > > Sorry, I think I also misunderstood you too. :( > I think kernel still has some compatible problems. I just skimmed > it again, and I found a problem. > > In RELENG_4, I found sys/i386/i386/machdep.c has following code in > sendsig(): > > > sf.sf_signum = sig; > sf.sf_ucontext = (register_t)&sfp->sf_uc; > if (SIGISMEMBER(p->p_sigacts->ps_siginfo, sig)) { > /* Signal handler installed with SA_SIGINFO. */ > sf.sf_siginfo = (register_t)&sfp->sf_si; > sf.sf_ahu.sf_action = (__siginfohandler_t *)catcher; > > /* fill siginfo structure */ > sf.sf_si.si_signo = sig; > sf.sf_si.si_code = code; > sf.sf_si.si_addr = (void*)regs->tf_err; > } > else { > /* Old FreeBSD-style arguments. */ > sf.sf_siginfo = code; > sf.sf_addr = regs->tf_err; <------- > sf.sf_ahu.sf_handler = catcher; > } > > the sf.sf_addr is assigned by tf_err here. > > In later branch ( I don't know which ), it seems it uses ksi.ksi_addr, > > /* Old FreeBSD-style arguments. */ > sf.sf_arg2 = ksi->ksi_code; > sf.sf_addr = (register_t)ksi->ksi_addr; > sf.sf_ahu.sf_handler = catcher; > > > > the tf_err may not be equal to ksi_addr! This may need to be fixed. > The change was introduced by r151316 | davidxu | 2005-10-14 /* Old FreeBSD-style arguments. */ - sf.sf_siginfo = code; - sf.sf_addr = regs->tf_err; + sf.sf_siginfo = ksi->ksi_code; + sf.sf_addr = (register_t)ksi->ksi_addr; sf.sf_ahu.sf_handler = catcher;
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