bionic/libc/docs/CHANGES.TXT
David 'Digit' Turner ba9c6f0989 bionic: pthread: use private futexes by default for mutexes and condvars
Private futexes are a recent kernel addition: faster futexes that cannot be
shared between processes. This patch uses them by default, unless the PROCESS_SHARED
attribute flag is used when creating a mutex and/or conditional variable.

Also introduces pthread_condattr_init/destroy/setpshared/getpshared.

Change-Id: I3a0e2116f467072b046524cb5babc00e41057a53
2010-03-11 11:48:38 -08:00

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Bionic ChangeLog:
-----------------
Differences between current and Android 2.1:
- Add support for SH-4 CPU architecture !
- __atomic_swap(): use LDREX/STREX CPU instructions on ARMv6 and higher.
- <arpa/telnet.h>: New header (declarations only, no implementation).
- <err.h>: New header + implementation. GLibc compatibility.
- <warn.h>: New header + implementation. GLibc compatibility.
- <fts.h>: New header + implementation.
- <mntent.h>: Add missing <stdio.h> include.
- <regex.h>: New header + implementation.
- <signal.h>: Added killpg()
- <stdint.h>: Allow 64-bit type declarations on C99 builds.
- <stdio.h>: Add fdprintf() and vfdprintf(). Note that GLibc provides
the confusing 'dprintf' and 'vdprintf()' functions instead.
- <stdlib.h>: Fix ptsname_r(): the return type is int instead of char*.
The mistake comes from a GLibc man page bug (the man page listed a return
type of char*, while the implementation used int. Fixed in late 2009 only).
The Bionic implementation was incorrect. Technically, this is an ABI
breakage, but code that used this function probably never worked or
compiled properly anyway.
- <strings.h>: Add missing <sys/types.h> include.
- <sys/queue.h>: Added new header (no implementation - macro templates).
- <sys/resource.h>: Add rlim_t proper definition.
- <time64.h>: Add missing C++ header inclusion guards.
- <unistd.h>: Add getusershell(), setusershell() and endusershell(), though
implementation are bogus. GLibc compatibility.
- <wchar.h>: Add mbstowcs() and wcstombs()
- add clone() implementation for ARM (x86 and SH-4 not working yet).
- <sys/epoll.h>: <sys/system_properties.h>: Add missing C++ inclusion guards
- fix getpwnam() and getpwgrp() to accept "app_0" as a valid user name.
- fix sem_trywait() to return -1 and set errno to EAGAIN, instead of
returning EAGAIN directly.
- fix sem_post() to wake up multiple threads when called rapidly in
succession.
- DNS: partial implementation of RFC3484 (rule 1, 2, 5, 6, 8, 10 and
modified rule 9), for better address selection/sorting.
In the process, removed code that was previously used for "sortlist"
in /etc/resolv.conf. (resolv.conf is already ignored, so the latter
is a no-op for actual functionality.)
- fix pthread_sigmask() to properly return an error code without touching
errno. Previous implementation returned -1 on error, setting errno, which
is not Posix compliant.
- add sigaltstack() implementation for ARM.
- <time.h>: Properly implement the 'timezone' and 'daylight' global variables
(they were not defined previously, though declared in the header).
- <time.h>: Fix timezone management implementation to properly update
'tm_gmtoff' field in 'struct tm' structure.
- DNS: get rid of spurious random DNS queries when trying to resolve
an unknown domain name. Due to an initialization bug, a random DNS search
list was generated for each thread is net.dns.search is not defined.
- <pthread.h>: Add pthread_condattr_init/destroy/setpshared/getpshared.
Also modify mutex and condvar implementation to use private futexes by
default, unless PROCESS_SHARED is specified in the init attributes.
Private futexes are limited to a single address space and can't be shared
among processes. However they are much faster to wake/wait for. This should
speed up mutex and condvar operations.
NOTE: PROCESS_SHARED mutexes are still NOT robust (see note below).
-------------------------------------------------------------------------------
Differences between Android 2.1 and 2.0.1:
- zoneinfo: updated data tables to version 2009s
-------------------------------------------------------------------------------
Differences between Android 2.0.1 and 2.0:
- abort(): ARM-specific hack to preserve the 'lr' register when abort()
is called (GCC does not preserve it by default since it thinks that
abort() never returns). This improves stack traces considerably.
-------------------------------------------------------------------------------
Differences between Android 2.0 and 1.6:
- memcmp(), memcpy(): ARMv7 optimized versions.
- pthread_mutexattr_setpshared(): implementation will not return ENOTSUP
if PTHREAD_PROCESS_SHARED is used, because our Mutex implementation can
work across multiple processes.
*HOWEVER* it does not use "robust futexes" which means that held mutexes
*are not* automatically released by the kernel when the owner process
crashes or exits. This is only done to simplify communication between
two always-live system processes, DO NOT USE THIS IN APPLICATIONS !
- pthread_mutex_lock_timeout_np(): New Android-specific function to
perform a timed lock (). In case of timeout, it returns EBUSY.
- pthread_cond_timedwait_monotonic_np(): Same as pthread_cond_timedwait()
but uses the monotonic clock(). Android-specific.
- pthread_cond_timedwait_relative_np(): Same as pthread_cond_timedwait()
but uses a relative timeout instead. Android-specific.
- <netinet/in.h>: Now includes <netinet/in6.h>.
- <netinet/in6.h>: Added IPV6_JOIN_GROUP, IPV6_LEAVE_GROUP, IN6ADDR_ANY_INIT
and ipv6mr_interface definitions.
- <time.h>:
* Add missing tzset() declaration.
* Add Android-specific strftime_tz().
- getaddrinfo():
Only perform IPv6 lookup for AF_UNSPEC if we have IPv6 connectivity.
This saves one DNS query per lookup on non-IPv6 systems.
- mktime(): Fix an infinite loop problen that appeared when switching to
GCC 4.4.0.
- strftime(): fix incorrect handling of dates > 2038 due to 64-bit issue
in original code.
-------------------------------------------------------------------------------
Differences between Android 1.6 and 1.5:
- C runtime: Fix runtime initialization to be called before any static C++
constructors. This allows these to use pthread functions properly.
- __aeabi_atexit(): Fix implementation to properly call C++ static destructors
when the program exits (or when a shared library is unloaded).
- <sys/stat.h>: added GLibc compatibility macros definitions:
#define st_atimensec st_atime_nsec
#define st_mtimensec st_mtime_nsec
#define st_ctimensec st_ctime_nsec
- getaddrinfo(): implementation will now allow numeric ports if ai_socktype is
set to ANY. This is to match the GLibc behaviour.
- getservent(): and getservent_r() incorrectly returned the port in host-endian
order in the s_port field. It now returns it in big-endian order.
- DNS: Allow underscore in the middle of DNS labels. While not really
standard, this extension is needed for some VPN configurations and is
supported by other operating systems.
- DNS: Support for DNS domain search lists through the new net.dns.search
system property. The corresponding value must be a space-separated list of
domain suffixes.