The function closes all open file descriptors greater than or equal to
input argument. Negative values are clamped to 0, i.e, it will close
all file descriptors.
As indicated by the bug report, this is a common symbol provided by
different systems (Solaris, OpenBSD, NetBSD, FreeBSD) and, although
its has inherent issues with not taking in consideration internal libc
file descriptors (such as syslog), this is also a common feature used
in multiple projects [1][2][3][4][5].
The Linux fallback implementation iterates over /proc and close all
file descriptors sequentially. Although it was raised the questioning
whether getdents on /proc/self/fd might return disjointed entries
when file descriptor are closed; it does not seems the case on my
testing on multiple kernel (v4.18, v5.4, v5.9) and the same strategy
is used on different projects [1][2][3][5].
Also, the interface is set a fail-safe meaning that a failure in the
fallback results in a process abort.
Checked on x86_64-linux-gnu and i686-linux-gnu on kernel 5.11 and 4.15.
[1] 5238e95759/src/basic/fd-util.c (L217)
[2] ddf4b77e11/src/lxc/start.c (L236)
[3] 9e4f2f3a6b/Modules/_posixsubprocess.c (L220)
[4] 5f47c0613e/src/libstd/sys/unix/process2.rs (L303-L308)
[5] https://github.com/openjdk/jdk/blob/master/src/java.base/unix/native/libjava/childproc.c#L82
It was added on Linux 5.9 (278a5fbaed89) with CLOSE_RANGE_CLOEXEC
added on 5.11 (582f1fb6b721f). Although FreeBSD has added the same
syscall, this only adds the symbol on Linux ports. This syscall is
required to provided a fail-safe way to implement the closefrom
symbol (BZ #10353).
Checked on x86_64-linux-gnu and i686-linux-gnu on kernel 5.11 and 4.15.
Now that there are no internal users anymore, these new symbol
versions can be removed from the public ABI. The compatibility
symbols remain.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This patch consolidates the setsockopt implementation on
sysdeps/unix/sysv/linux/getsockopt.c. The changes are:
1. Remove it from auto-generation syscalls.list on all architectures.
2. Add __ASSUME_SETSOCKOPT_SYSCALL as default and undef if for
specific kernel versions on some architectures.
This also fix a potential issue where 32-bit time_t ABI should use the
linux setsockopt which overrides the underlying SO_* constants used for
socket timestamping for _TIME_BITS=64.
Checked on x86_64-linux-gnu and i686-linux-gnu.
This patch consolidates the getsockopt Linux syscall implementation on
sysdeps/unix/sysv/linux/getsockopt.c. The changes are:
1. Remove it from auto-generation syscalls.list on all architectures.
2. Add __ASSUME_GETSOCKOPT_SYSCALL as default and undef if for
specific kernel versions on some architectures.
This also fix a potential issue where 32-bit time_t ABI should use the
linux getsockopt which overrides the underlying SO_* constants used for
socket timestamping for _TIME_BITS=64.
Checked on x86_64-linux-gnu and i686-linux-gnu.
The symbols gai_cancel, gai_error, gai_suspend, getaddrinfo_a,
__gai_suspend_time64 were moved using scripts/move-symbol-to-libc.py.
For Hurd (which remains !PTHREAD_IN_LIBC), a few #define redirects
had to be added because several pthread functions are not available
under __. (Linux uses __ prefixes for most hidden aliases, and has
to in some cases to avoid linknamespace issues.)
Linux 5.13 has three new syscalls (landlock_create_ruleset,
landlock_add_rule, landlock_restrict_self). Update syscall-names.list
and regenerate the arch-syscall.h headers with build-many-glibcs.py
update-syscalls.
Tested with build-many-glibcs.py.
The symbols forkpty, login, login_tty, logout, logwtmp, openpty
were moved using scripts/move-symbol-to-libc.py.
This is a single commit because most of the symbols are tied together
via forkpty, for example.
Several changes to use hidden prototypes are needed. This commit
also updates pseudoterminal terminology on modified lines.
For 390 (31-bit), this commit follows the existing style for the
compat symbol version creation.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Austin Group issue 62 [1] dropped the async-signal-safe requirement
for fork and provided a async-signal-safe _Fork replacement that
does not run the atfork handlers. It will be included in the next
POSIX standard.
It allow to close a long standing issue to make fork AS-safe (BZ#4737).
As indicated on the bug, besides the internal lock for the atfork
handlers itself; there is no guarantee that the handlers itself will
not introduce more AS-safe issues.
The idea is synchronize fork with the required internal locks to allow
children in multithread processes to use mostly of standard function
(even though POSIX states only AS-safe function should be used). On
signal handles, _Fork should be used intead and only AS-safe functions
should be used.
For testing, the new tst-_Fork only check basic usage. I also added
a new tst-mallocfork3 which uses the same strategy to check for
deadlock of tst-mallocfork2 but using threads instead of subprocesses
(and it does deadlock if it replaces _Fork with fork).
[1] https://austingroupbugs.net/view.php?id=62
The symbols were moved using scripts/move-symbol-to-libc.py.
The way the ABI intransition is implemented is changed with this
commit: the implementation is now consolidated in one file with a
TIMER_T_WAS_INT_COMPAT check.
The shared librt is now empty, so this commit adds a placeholder
symbol at the base version, GLIBC_2.2, and potentially at the
GLIBC_2.3.3 version as well (the leftover from the int/timer_t ABI
transition).
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
The way the ABI intransition is implemented is changed with this
commit: the implementation is now consolidated in one file with a
TIMER_T_WAS_INT_COMPAT check.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
The way the ABI intransition is implemented is changed with this
commit: the implementation is now consolidated in one file with a
TIMER_T_WAS_INT_COMPAT check.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
timer_create and timer_delete are tied together via the int/timer_t
compatibility code. The way the ABI intransition is implemented
is changed with this commit: the implementation is now consolidated
in one file with a TIMER_T_WAS_INT_COMPAT check.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This is almost equivalent to __WORDSIZE == 64
&& OTHER_SHLIB_COMPAT (librt, GLIBC_2_1, GLIBC_2_3_3), except
that this expression is true for mips64/n64 targets as well,
even though those did not undergo the timer_t transition.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The symbol was moved using scripts/move-symbol-to-libc.py.
A placeholder symbol is needed on some architectures for the
GLIBC_2.3.4 version.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
A placeholder symbol is required to keep the GLIBC_2.7 version.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
An explicit call from fork into the mq_notify implementation replaces
the previous use of pthread_atfork.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
To introduce the proper symbol versioning, the implementation of
the system call wrapper us moved to a C file.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
Placeholder symbols are needed on some architectures, to keep the
GLIBC_2.1 and GLIBC_2.4 symbol versions around.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
Both symbols have to be moved at the same time because they
are intertwined for __WORDSIZE == 64. The treatment of this case
is also changed to match more closely how the other files suppress
the declaration of the *64 identifier.
The symbols were moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
There is a minor oddity here: This is generic code shared with Hurd,
and Hurd does not have time64 support. This is why the
versioned_symbol export for __aio_suspend_time64 is restricted to
the PTHREAD_IN_LIBC code.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
Both symbols have to be moved at the same time because they
are intertwined for __WORDSIZE == 64. The treatment of this case
is also changed to match more closely how the other files suppress
the declaration of the *64 identifier.
The symbols were moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
A version placeholder symbol is needed on alpha and sparc because
of the additional symbols formerly at version GLIBC_2.3.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>:
This commit also moves the aio_misc and aio_sigquue helper,
so GLIBC_PRIVATE exports need to be added.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This function has no dependency on libpthread, so the move is also
applied to Hurd.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This function has no dependency on libpthread, so the move is also
applied to Hurd.
To avoid localplt failures, use __open64_nocancel instead of
pthread_setcancelstate and open.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
These were turned into compat symbols as part of the libpthread
move. It turns out they are used by language run-time libraries
(e.g., the GCC D front end), so it makes to preserve them as
external symbols even though they are not declared in any header
file.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Similar to fts, ftw routines passes a stat pointer that might
differ of size and layout when 64-bit time API is used.
Checked on i686-linux-gnu and x86_64-linux-gnu.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Similar to glob, fts routines passes a stat pointer that might
differ of size and layout when 64-bit time API is used.
Checked on i686-linux-gnu and x86_64-linux-gnu.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
The glob might pass a different stat struct for gl_stat and gl_lstat
when GLOB_ALTDIRFUNC is used. This requires add a new 64-bit time
version that also uses 64-bit time stat functions.
Checked on i686-linux-gnu and x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
A new build flag, _TIME_BITS, enables the usage of the newer 64-bit
time symbols for legacy ABI (where 32-bit time_t is default). The 64
bit time support is only enabled if LFS (_FILE_OFFSET_BITS=64) is
also used.
Different than LFS support, the y2038 symbols are added only for the
required ABIs (armhf, csky, hppa, i386, m68k, microblaze, mips32,
mips64-n32, nios2, powerpc32, sparc32, s390-32, and sh). The ABIs with
64-bit time support are unchanged, both for symbol and types
redirection.
On Linux the full 64-bit time support requires a minimum of kernel
version v5.1. Otherwise, the 32-bit fallbacks are used and might
results in error with overflow return code (EOVERFLOW).
The i686-gnu does not yet support 64-bit time.
This patch exports following rediretions to support 64-bit time:
* libc:
adjtime
adjtimex
clock_adjtime
clock_getres
clock_gettime
clock_nanosleep
clock_settime
cnd_timedwait
ctime
ctime_r
difftime
fstat
fstatat
futimens
futimes
futimesat
getitimer
getrusage
gettimeofday
gmtime
gmtime_r
localtime
localtime_r
lstat_time
lutimes
mktime
msgctl
mtx_timedlock
nanosleep
nanosleep
ntp_gettime
ntp_gettimex
ppoll
pselec
pselect
pthread_clockjoin_np
pthread_cond_clockwait
pthread_cond_timedwait
pthread_mutex_clocklock
pthread_mutex_timedlock
pthread_rwlock_clockrdlock
pthread_rwlock_clockwrlock
pthread_rwlock_timedrdlock
pthread_rwlock_timedwrlock
pthread_timedjoin_np
recvmmsg
sched_rr_get_interval
select
sem_clockwait
semctl
semtimedop
sem_timedwait
setitimer
settimeofday
shmctl
sigtimedwait
stat
thrd_sleep
time
timegm
timerfd_gettime
timerfd_settime
timespec_get
utime
utimensat
utimes
utimes
wait3
wait4
* librt:
aio_suspend
mq_timedreceive
mq_timedsend
timer_gettime
timer_settime
* libanl:
gai_suspend
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
It is only used for !__USE_MISC, the default way uses the kernel
headers. The patch also adds the SO_TIMESTAMP, SO_TIMESTAMPNS, and
SO_TIMESTAMPING which uses new values for 64-bit time_t kernel
interfaces.
The __USE_TIME_BITS64 is not defined internally yet, although the
internal header is used when building the 64-bit stat implementations.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Instead of replicate the same definitions from struct_shmid64_ds.h
on the multiple struct_shmid_ds.h, use a common header which is included
when required (struct_shmid64_ds_helper.h).
The __USE_TIME_BITS64 is not defined internally yet, although the
internal header is used when building the 64-bit semctl implementation.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Instead of replicate the same definitions from struct_semid64_ds.h
on the multiple struct_semid_ds.h, use a common header which is included
when required (struct_semid64_ds_helper.h).
The __USE_TIME_BITS64 is not defined internally yet, although the
internal header is used when building the 64-bit semctl implementation.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Instead of replicate the same definitions from struct_msqid64_ds.h
on the multiple struct_msqid_ds.h, use a common header which is included
when required (struct_msqid64_ds_helper.h).
The __USE_TIME_BITS64 is not defined internally yet, although the
internal header is used when building the 64-bit stat implementations.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Instead of replicate the same definitions from struct_stat_time64.h
on the multiple struct_stat.h, use a common header which is included
when required (struct_stat_time64_helper.h). The 64-bit time support
is added only for LFS support.
The __USE_TIME_BITS64 is not defined internally yet, although the
internal header is used when building the 64-bit stat implementations.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
The recvmsg handling is more complicated because it requires check the
returned kernel control message and make some convertions. For
!__ASSUME_TIME64_SYSCALLS it converts the first 32-bit time SO_TIMESTAMP
or SO_TIMESTAMPNS and appends it to the control buffer if has extra
space or returns MSG_CTRUNC otherwise. The 32-bit time field is kept
as-is.
Calls with __TIMESIZE=32 will see the converted 64-bit time control
messages as spurious control message of unknown type. Calls with
__TIMESIZE=64 running on pre-time64 kernels will see the original
message as a spurious control ones of unknown typ while running on
kernel with native 64-bit time support will only see the time64 version
of the control message.
Checked on x86_64-linux-gnu and i686-linux-gnu (on 5.4 and on 4.15
kernel).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
The constant values will be changed for __TIMESIZE=64, so binaries built
with 64-bit time support might fail to work properly on old kernels.
Both {get,set}sockopt will retry the syscall with the old constant
values and the timeout value adjusted when kernel returns ENOTPROTOPT.
It also adds an internal only SO_{RCV,SND}TIMEO where
COMPAT_SO_{RCV,SND}TIMEO_OLD indicates pre 32-bit time support and
COMPAT_SO_{RCV,SND}TIMEO_NEW indicates time64 support. It allows to
refer to constant independently of the time_t ABI and kernel version
used.
Checked on x86_64-linux-gnu and i686-linux-gnu (on 5.4 and on 4.15
kernel).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Commit 68ab82f566 added support for the scv
syscall ABI on powerpc. Since then systems that have kernel and processor
support started using scv. However adding the proper support for a new syscall
ABI requires changes to several other projects (e.g. qemu, valgrind, strace,
kernel), which are gradually receiving support.
Meanwhile, having a way to disable scv on glibc at build time can be useful for
distros that may encounter conflicts with projects that still do not support the
scv ABI, buying time until proper support is added.
This commit adds a --disable-scv option that disables scv support and uses sc
for all syscalls, like before commit 68ab82f566.
Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com>
This patch replaced obsolete AC_TRY_COMPILE to AC_COMPILE_IFELSE or
AC_PREPROC_IFELSE.
It has been confirmed that GNU 'autoconf' 2.69 suppressed obsolete
warnings, updated the following files:
- configure
- sysdeps/mach/configure
- sysdeps/mach/hurd/configure
- sysdeps/s390/configure
- sysdeps/unix/sysv/linux/configure
and didn't change the following files:
- sysdeps/ieee754/ldbl-opt/configure
- sysdeps/unix/sysv/linux/powerpc/configure
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
In elf/Makefile, remove the $(libdl) dependency from testobj1.so
because it the unused libdl DSO now causes elf/tst-unused-deps to
fail.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
There is a minor functionality enhancement: dlerror now sets
errno if it was set as part of the exception. (This is the result
of using %m in asprintf, to avoid the strerror PLT call.) The
previous errno value upon function return was unpredictable.
Documenting this as a feature is premature; we need to make sure
that the error codes are meaningful when they are set by the dynamic
loader.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Some symbols have explicit versioned_symbol or compat_symbol markers
in the sources, but no corresponding entry in the Versions files.
This presently works because the local: * directive is only applied
to the base version.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Only the placeholder compatibility symbols are left now.
The __errno_location symbol was removed (moved) using
scripts/move-symbol-to-libc.py.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
The libpthread placeholder symbols need some changes because some
symbol versions have gone away completely. But
__errno_location@@GLIBC_2.0 still exists, so the GLIBC_2.0 version
is still there.
The internal __pthread_create symbol now points to the correct
function, so the sysdeps/nptl/thrd_create.c override is no longer
necessary.
There was an issue how the hidden alias of pthread_getattr_default_np
was defined, so this commit cleans up that aspects and removes the
GLIBC_PRIVATE export altogether.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
ISO C2X adds a timespec_getres function alongside the C11
timespec_get, with functionality similar to that of POSIX clock_getres
(including allowing a NULL pointer to be passed to the function).
Implement this function for glibc, similarly to the implementation of
timespec_get.
This includes a basic test like that of timespec_get, but no
documentation in the manual, given that TIME_UTC and timespec_get
aren't documented in the manual at all. The handling of 64-bit time
follows that in timespec_get; people maintaining patch series for
64-bit time will need to update them accordingly (to export
__timespec_getres64, redirect calls in time.h and run the test for
_TIME_BITS=64).
Tested for x86_64 and x86, and (previous version; only testcase
differs) with build-many-glibcs.py.
The symbol was moved using scripts/move-symbol-to-libc.py.
The GLIBC_2.11 version is now empty, so add a placeholder symbol.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
The GLIBC_2.3.4 version is now empty, so add a placeholder symbol.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
Add __libpthread_version_placeholder@@GLIBC_2.12 for the targets
that need it.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
__libpthread_version_placeholder@@GLIBC_2.2 is needed by this change;
the Versions entry for GLIBC_2.2 in libpthread had leftover symbols
due to an error in a previous conflict resolution. The condition
for the placeholder symbol is complicated because some architectures
have earlier symbols at the GLIBC_2.2 symbol versions, so the
placeholder is not required there (yet).
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
A new placeholder symbol __libpthread_version_placeholder@GLIBC_2.18
is needed to keep the GLIBC_2.18 symbol version in libpthread.
The __pthread_getattr_default_np@@GLIBC_PRIVATE export is used
from pthread_create.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py,
in one commit due to their dependency on the internal
__concurrency_level variable.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbols were moved using scripts/move-symbol-to-libc.py.
Also clean up some unwinder linking leftover in the same spot
in nptl/pthreadP.h.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
It is necessary to arrange for a
__libpthread_version_placeholder@GLIBC_2.6 on some of the powerpc
targets.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbols pthread_clockjoin_np, pthread_join, pthread_timedjoin_np,
pthread_tryjoin_np, thrd_join were moved using
scripts/move-symbol-to-libc.py.
Moving the symbols at the same time avoids the need for temporary
exports.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The symbol was moved using scripts/move-symbol-to-libc.py.
The export of __default_pthread_attr_freeres is temporary. There
is a minor regression in freeres coverage because in the dynamic case,
__default_pthread_attr_freeres is no longer called if libpthread is
not linked in.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The nptl version is used as default, since now with symbol always
present the single-thread optimization is tricky.
Hurd is not change, it is used it own lock scheme (which call
_cthreads_funlockfile).
Checked on x86_64-linux-gnu.
The nptl version is used as default, since now with symbol always
present the single-thread optimization is tricky.
Hurd is not change, it is used it own lock scheme (which call
_cthreads_ftrylockfile).
Checked on x86_64-linux-gnu.
The nptl version is used as default, since now with symbol always
present the single-thread optimization is tricky.
Hurd is not change, it is used it own lock scheme (which call
_cthreads_flockfile).
Checked on x86_64-linux-gnu.
The symbol was moved using scripts/move-symbol-to-libc.py.
A small adjust to the sem_unlink implementation is necessary to avoid
a check-localplt failure.
A placeholder symbol to keep the GLIBC_2.1.1 version alive in
libpthread is added with this commit.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
