Date: Thu, 2 Sep 2010 12:26:33 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: David Xu <davidxu@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r212076 - head/lib/libthr/thread Message-ID: <20100902092633.GM2396@deviant.kiev.zoral.com.ua> In-Reply-To: <4C7FD8D1.1000702@freebsd.org> References: <201009010218.o812IX5G048257@svn.freebsd.org> <20100902081136.GG2396@deviant.kiev.zoral.com.ua> <4C7FD232.9080100@freebsd.org> <20100902084116.GJ2396@deviant.kiev.zoral.com.ua> <4C7FD8D1.1000702@freebsd.org>
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--EEu/qcNrcbWqPwHS Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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 expensiv= e. > >>>> The signal handler wrapper works in this way: > >>>> 1) libthr installs its signal handler if user code invokes sigacti= on > >>>> 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=20 > >>>> 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 temporar= ily > >>>> disabled, after user signal handler is returned, cancellation= =20 > >>>> 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) !=3D 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 :(. >=20 > 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. >=20 > In RELENG_4, I found sys/i386/i386/machdep.c has following code in > sendsig(): >=20 >=20 > sf.sf_signum =3D sig; > sf.sf_ucontext =3D (register_t)&sfp->sf_uc; > if (SIGISMEMBER(p->p_sigacts->ps_siginfo, sig)) { > /* Signal handler installed with SA_SIGINFO. */ > sf.sf_siginfo =3D (register_t)&sfp->sf_si; > sf.sf_ahu.sf_action =3D (__siginfohandler_t *)catcher; >=20 > /* fill siginfo structure */ > sf.sf_si.si_signo =3D sig; > sf.sf_si.si_code =3D code; > sf.sf_si.si_addr =3D (void*)regs->tf_err; > } > else { > /* Old FreeBSD-style arguments. */ > sf.sf_siginfo =3D code; > sf.sf_addr =3D regs->tf_err; <------- > sf.sf_ahu.sf_handler =3D catcher; > } >=20 > the sf.sf_addr is assigned by tf_err here. >=20 > In later branch ( I don't know which ), it seems it uses ksi.ksi_addr, >=20 > /* Old FreeBSD-style arguments. */ > sf.sf_arg2 =3D ksi->ksi_code; > sf.sf_addr =3D (register_t)ksi->ksi_addr; > sf.sf_ahu.sf_handler =3D catcher; >=20 >=20 >=20 > the tf_err may not be equal to ksi_addr! This may need to be fixed. >=20 The change was introduced by r151316 | davidxu | 2005-10-14 /* Old FreeBSD-style arguments. */ - sf.sf_siginfo =3D code; - sf.sf_addr =3D regs->tf_err; + sf.sf_siginfo =3D ksi->ksi_code; + sf.sf_addr =3D (register_t)ksi->ksi_addr; sf.sf_ahu.sf_handler =3D catcher; --EEu/qcNrcbWqPwHS Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkx/bckACgkQC3+MBN1Mb4jDewCg9oK3MITarwsG1hpppvsS5V/y ZAQAoITzHIw/F10pF2XYQM9pRzPRjsve =BWAc -----END PGP SIGNATURE----- --EEu/qcNrcbWqPwHS--
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