Date: Thu, 2 Sep 2010 11:11:36 +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: <20100902081136.GG2396@deviant.kiev.zoral.com.ua> In-Reply-To: <201009010218.o812IX5G048257@svn.freebsd.org> References: <201009010218.o812IX5G048257@svn.freebsd.org>
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--DNWMrkyqDUV26QiQ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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 >=20 > 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) !=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. --DNWMrkyqDUV26QiQ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkx/XDgACgkQC3+MBN1Mb4iwWQCgjjl5Xxc5WHgKeHE+VJ5cpPpu vmAAn1Ez/iXX4u9dZCd+mU7aJ9k0+Jhu =42+D -----END PGP SIGNATURE----- --DNWMrkyqDUV26QiQ--
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