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musl - an implementation of the standard library for Linux-based systems
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Jens Gustedt 47d0bcd476 new lock algorithm with state and congestion count in one atomic int 
A variant of this new lock algorithm has been presented at SAC'16, see
https://hal.inria.fr/hal-01304108. A full version of that paper is
available at https://hal.inria.fr/hal-01236734.

The main motivation of this is to improve on the safety of the basic lock
implementation in musl. This is achieved by squeezing a lock flag and a
congestion count (= threads inside the critical section) into a single
int. Thereby an unlock operation does exactly one memory
transfer (a_fetch_add) and never touches the value again, but still
detects if a waiter has to be woken up.

This is a fix of a use-after-free bug in pthread_detach that had
temporarily been patched. Therefore this patch also reverts

         c1e27367a9

This is also the only place where internal knowledge of the lock
algorithm is used.

The main price for the improved safety is a little bit larger code.

Under high congestion, the scheduling behavior will be different
compared to the previous algorithm. In that case, a successful
put-to-sleep may appear out of order compared to the arrival in the
critical section.
2018-01-09 13:10:12 -05:00
arch fix x32 unistd macros to report as ILP32 not LP64 2017-12-14 21:22:51 -05:00
crt add s390x port 2016-11-11 23:06:21 -05:00
dist add another example option to dist/config.mak 2012-04-24 16:49:11 -04:00
include add additional uapi guards for Linux kernel header files 2018-01-09 13:08:25 -05:00
ldso fix malloc state corruption when ldso rejects loading a second libc 2017-11-13 15:27:10 -05:00
src new lock algorithm with state and congestion count in one atomic int 2018-01-09 13:10:12 -05:00
tools add CFI generation script for x86_64 2015-10-13 18:09:46 -04:00
.gitignore remove obsolete gitignore rules 2016-07-06 00:21:25 -04:00
configure disable global visibility override hack (vis.h) by default 2017-08-11 00:17:00 -04:00
COPYRIGHT update COPYRIGHT file to clarify that permissions apply for all files 2016-04-28 20:41:45 -04:00
INSTALL add powerpc64 and s390x to list of supported archs in INSTALL file 2017-08-29 20:48:02 -04:00
Makefile remove unused explicit dependency rules for crti/crtn 2017-12-14 23:19:34 -05:00
README update version reference in the README file 2014-06-25 14:16:53 -04:00
VERSION release 1.1.18 2017-10-31 15:13:58 -04:00
WHATSNEW release 1.1.18 2017-10-31 15:13:58 -04:00

README 

    musl libc

musl, pronounced like the word "mussel", is an MIT-licensed
implementation of the standard C library targetting the Linux syscall
API, suitable for use in a wide range of deployment environments. musl
offers efficient static and dynamic linking support, lightweight code
and low runtime overhead, strong fail-safe guarantees under correct
usage, and correctness in the sense of standards conformance and
safety. musl is built on the principle that these goals are best
achieved through simple code that is easy to understand and maintain.

The 1.1 release series for musl features coverage for all interfaces
defined in ISO C99 and POSIX 2008 base, along with a number of
non-standardized interfaces for compatibility with Linux, BSD, and
glibc functionality.

For basic installation instructions, see the included INSTALL file.
Information on full musl-targeted compiler toolchains, system
bootstrapping, and Linux distributions built on musl can be found on
the project website:

    http://www.musl-libc.org/