Date: Sat, 12 Jan 2013 07:32:52 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: davidxu@freebsd.org Cc: arch@freebsd.org, Jilles Tjoelker <jilles@stack.nl>, toolchain@freebsd.org Subject: Re: Fast sigblock (AKA rtld speedup) Message-ID: <20130112053252.GI2561@kib.kiev.ua> In-Reply-To: <50F0ADDA.4000801@gmail.com> References: <20130107182235.GA65279@kib.kiev.ua> <20130111095459.GZ2561@kib.kiev.ua> <50EFE830.3030500@freebsd.org> <20130111204938.GD2561@kib.kiev.ua> <20130111232906.GA29017@stack.nl> <50F0ADDA.4000801@gmail.com>
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--O2lvLMQR9k8T/RyB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Jan 12, 2013 at 08:27:06AM +0800, David Xu wrote: > On 2013/01/12 07:29, Jilles Tjoelker wrote: > > On Fri, Jan 11, 2013 at 10:49:38PM +0200, Konstantin Belousov wrote: > >> http://people.freebsd.org/~kib/misc/rtld-sigblock.3.patch > > The new fields td_sigblock_ptr and td_sigblock_val are in the part that > > is zeroed for new threads, while the code in rtld appears to expect them > > to be copied (on fork, vfork and pthread_create). The fields are > > correctly zeroed on exec. > > > > Sharing the magic variable between threads means that one thread holding > > an rtld lock will block signals for all other threads as well. This is > > different from how the normal signal mask works but I don't know whether > > it may break things. However, the patch depends on it in some way > > because sigtd() does not know about fast sigblock and will therefore > > happily select a thread that is fast-sigblocking to handle a signal > > directed at the process. > > > > Although libthr's postpone approach is somewhat ugly, it does not depend > > on any non-standard kernel features and does not delay the default > > action. Would it be possible to move that code to libc to make things > > easier for rtld? It looks like this requires teaching libc about various > > threading concepts, though. > Long time ago, if i remembered correctly, kib said that he wanted to > merge libthr code into libc, I don't know its state. Yes, this is correct, and I still want this. >=20 > > Something feels ugly about not allowing applications to use this, > > although I don't know how it would work. On the other hand, the strange > > signal state created by this and implicit assumptions that the duration > > will be short may be a reason to restrict its use to a relatively small > > piece of code. > > > True, it seems it is for short duration. --O2lvLMQR9k8T/RyB Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iQIcBAEBAgAGBQJQ8PWDAAoJEJDCuSvBvK1BDgUP/iWJXQukG9XrXeguc+y+bAOf VcWtQfyWdFz0ZsOLdKH6z/gnRF/yiQynvp+na+rtq0rgWDBXIQ7uP0ZKItAevfkW nFM7s12Gv1bQNQq59uFeyshU97ORHCk11ZpjLs84mcKPDWEyAsZQAxRXhz5oTSSL SAkV3ooYeE6eSuFA6ZQgUT3WKDbTwpTTm1mTjGjnPWrRYNrKkrNNZ2P6E7uANawi GWMX0sMbrhtrrmrwUPNdR7ny8jqcaQrCvLxZ+73cVEQBIZIhEuHt9QxqEwZm+OYX v9xV4cSZfCLC2HA/zVxzch5HL+ZExBKDVkSx0K394giPzjlymJePq18VgiBTcozj 6tRPNaWNzUZj9ACwbXsr9sGPuv+/e3VqAR0b5nREOatqy2ha04Q80PZpyIf9Umwx 7D8qsRxmhQJhWfvPevaOeD22OuCy2Wv9qQ76p6OnprsNt8VMStMnBKoxpBL024Na 6VsUaK3QpI3zI1NLdzQyvbfXDd8pQBjYm6NC2Jv3ukX7uc1D3JXJtOESr1TnWyWe QwT8Nf1hLM24mtqJQRipYE4wYSEYXNK3A5v1eXCF3PG/VipQ/I4j+3WPOmDdS6xu E7y5hTNBlQvZuZIFb2FVcuvTuu3AgOB9hdmheZA/xJzsiHUy6dEYWrHST3FUhxHr d7lyOHIZ890gPcsouqy7 =YOKS -----END PGP SIGNATURE----- --O2lvLMQR9k8T/RyB--
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