Date: Tue, 7 Sep 2010 12:42:49 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: David Xu <davidxu@freebsd.org> Cc: freebsd-threads@freebsd.org Subject: Re: sigwait() cancellation point Message-ID: <20100907094249.GA2465@deviant.kiev.zoral.com.ua> In-Reply-To: <4C86787E.6070908@freebsd.org> References: <20100906220041.GA4729@stack.nl> <4C86787E.6070908@freebsd.org>
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[-- Attachment #1 --] On Tue, Sep 07, 2010 at 05:38:06PM +0000, David Xu wrote: > Jilles Tjoelker wrote: > >Our sigwait() implementation may not be POSIX-compliant as it returns > >EINTR when it is interrupted by a caught signal. (Unfortunately I can > >only find this in SUSv4 in the Rationale, B.2.3 Error Numbers, > >Disallowing Return of the [EINTR] Error Code; the sigwait() page in XSH > >does not list an [EINTR] error condition, but does not prohibit one > >either like pthread_mutex_lock() and various others do.) > > > >However, libthr's wrapper for sigwait() relies on EINTR. To keep > >the possibility of changing this to be what POSIX intends, it would be > >nice to remove this dependency. > > > >One way is to include SIGCANCEL in the set of waited signals, but this > >requires two additional syscalls to mask/unmask SIGCANCEL. > > > >Another way is to use sigwaitinfo() in the wrapper, which is permitted > >to return [EINTR]. If [EINTR] is removed from the kernel sigwait(), > >looping on [EINTR] can then be implemented in the wrapper. > > > >Calling pthread_exit from the SIGCANCEL handler is not possible as this > >leaves the program in doubt about any signal consumed by sigwait(). > > > I have worked out a patch: > > http://people.freebsd.org/~davidxu/patch/sigwait.diff Isn't __sys_sigwait() supposed to return -1 and set errno ? [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkyGCRkACgkQC3+MBN1Mb4h+OACg7hfjTQxIBo51l48MFze1jB53 togAoMLB2WBbXhiK3kze065He7fIGl05 =AZkA -----END PGP SIGNATURE-----
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