The include cleanup on dl-minimal.c removed too much for some
targets.
Also for Hurd, __sbrk is removed from localplt.data now that
tunables allocated memory through mmap.
Checked with a build for all affected architectures.
The close_range () function implements the same API as the Linux and
FreeBSD syscalls. It operates atomically and reliably. The specified
upper bound is clamped to the actual size of the file descriptor table;
it is expected that the most common use case is with last = UINT_MAX.
Like in the Linux syscall, it is also possible to pass the
CLOSE_RANGE_CLOEXEC flag to mark the file descriptors in the range
cloexec instead of acually closing them.
Also, add a Hurd version of the closefrom () function. Since unlike on
Linux, close_range () cannot fail due to being unuspported by the
running kernel, a fallback implementation is never necessary.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20211106153524.82700-1-bugaevc@gmail.com>
No bug.
This commit adds support for __memcmpeq() as a new ABI for all
targets. In this commit __memcmpeq() is implemented only as an alias
to the corresponding targets memcmp() implementation. __memcmpeq() is
added as a new symbol starting with GLIBC_2.35 and defined in string.h
with comments explaining its behavior. Basic tests that it is callable
and works where added in string/tester.c
As discussed in the proposal "Add new ABI '__memcmpeq()' to libc"
__memcmpeq() is essentially a reserved namespace for bcmp(). The means
is shares the same specifications as memcmp() except the return value
for non-equal byte sequences is any non-zero value. This is less
strict than memcmp()'s return value specification and can be better
optimized when a boolean return is all that is needed.
__memcmpeq() is meant to only be called by compilers if they can prove
that the return value of a memcmp() call is only used for its boolean
value.
All tests in string/tester.c passed. As well build succeeds on
x86_64-linux-gnu target.
5bf07e1b3a ("Linux: Simplify __opensock and fix race condition [BZ #28353]")
made __opensock try NETLINK then UNIX then INET. On the Hurd, only INET
knows about network interfaces, so better actually specify that in
if_index.
INTR_MSG_TRAP was tinkering with esp to make it point to
_hurd_intr_rpc_mach_msg's parameters, and notably use (&msg)[-1] which is
meaningless in C.
Instead, just push the parameters on the stack, which also avoids leaving
local variables of _hurd_intr_rpc_mach_msg below esp. We now also
properly express that OPTION and TIMEOUT may be updated during the trap
call.
C2X adds new <math.h> functions for floating-point maximum and
minimum, corresponding to the new operations that were added in IEEE
754-2019 because of concerns about the old operations not being
associative in the presence of signaling NaNs. fmaximum and fminimum
handle NaNs like most <math.h> functions (any NaN argument means the
result is a quiet NaN). fmaximum_num and fminimum_num handle both
quiet and signaling NaNs the way fmax and fmin handle quiet NaNs (if
one argument is a number and the other is a NaN, return the number),
but still raise "invalid" for a signaling NaN argument, making them
exceptions to the normal rule that a function with a floating-point
result raising "invalid" also returns a quiet NaN. fmaximum_mag,
fminimum_mag, fmaximum_mag_num and fminimum_mag_num are corresponding
functions returning the argument with greatest or least absolute
value. All these functions also treat +0 as greater than -0. There
are also corresponding <tgmath.h> type-generic macros.
Add these functions to glibc. The implementations use type-generic
templates based on those for fmax, fmin, fmaxmag and fminmag, and test
inputs are based on those for those functions with appropriate
adjustments to the expected results. The RISC-V maintainers might
wish to add optimized versions of fmaximum_num and fminimum_num (for
float and double), since RISC-V (F extension version 2.2 and later)
provides instructions corresponding to those functions - though it
might be at least as useful to add architecture-independent built-in
functions to GCC and teach the RISC-V back end to expand those
functions inline, which is what you generally want for functions that
can be implemented with a single instruction.
Tested for x86_64 and x86, and with build-many-glibcs.py.
This patch adds the narrowing fused multiply-add functions from TS
18661-1 / TS 18661-3 / C2X to glibc's libm: ffma, ffmal, dfmal,
f32fmaf64, f32fmaf32x, f32xfmaf64 for all configurations; f32fmaf64x,
f32fmaf128, f64fmaf64x, f64fmaf128, f32xfmaf64x, f32xfmaf128,
f64xfmaf128 for configurations with _Float64x and _Float128;
__f32fmaieee128 and __f64fmaieee128 aliases in the powerpc64le case
(for calls to ffmal and dfmal when long double is IEEE binary128).
Corresponding tgmath.h macro support is also added.
The changes are mostly similar to those for the other narrowing
functions previously added, especially that for sqrt, so the
description of those generally applies to this patch as well. As with
sqrt, I reused the same test inputs in auto-libm-test-in as for
non-narrowing fma rather than adding extra or separate inputs for
narrowing fma. The tests in libm-test-narrow-fma.inc also follow
those for non-narrowing fma.
The non-narrowing fma has a known bug (bug 6801) that it does not set
errno on errors (overflow, underflow, Inf * 0, Inf - Inf). Rather
than fixing this or having narrowing fma check for errors when
non-narrowing does not (complicating the cases when narrowing fma can
otherwise be an alias for a non-narrowing function), this patch does
not attempt to check for errors from narrowing fma and set errno; the
CHECK_NARROW_FMA macro is still present, but as a placeholder that
does nothing, and this missing errno setting is considered to be
covered by the existing bug rather than needing a separate open bug.
missing-errno annotations are duly added to many of the
auto-libm-test-in test inputs for fma.
This completes adding all the new functions from TS 18661-1 to glibc,
so will be followed by corresponding stdc-predef.h changes to define
__STDC_IEC_60559_BFP__ and __STDC_IEC_60559_COMPLEX__, as the support
for TS 18661-1 will be at a similar level to that for C standard
floating-point facilities up to C11 (pragmas not implemented, but
library functions done). (There are still further changes to be done
to implement changes to the types of fromfp functions from N2548.)
Tested as followed: natively with the full glibc testsuite for x86_64
(GCC 11, 7, 6) and x86 (GCC 11); with build-many-glibcs.py with GCC
11, 7 and 6; cross testing of math/ tests for powerpc64le, powerpc32
hard float, mips64 (all three ABIs, both hard and soft float). The
different GCC versions are to cover the different cases in tgmath.h
and tgmath.h tests properly (GCC 6 has _Float* only as typedefs in
glibc headers, GCC 7 has proper _Float* support, GCC 8 adds
__builtin_tgmath).
All the ports now have THREAD_GSCOPE_IN_TCB set to 1. Remove all
support for !THREAD_GSCOPE_IN_TCB, along with the definition itself.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20210915171110.226187-4-bugaevc@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
This is a new implementation of GSCOPE which largely mirrors its NPTL
counterpart. Same as in NPTL, instead of a global flag shared between
threads, there is now a per-thread GSCOPE flag stored in each thread's
TCB. This makes entering and exiting a GSCOPE faster at the expense of
making THREAD_GSCOPE_WAIT () slower.
The largest win is the elimination of many redundant gsync_wake () RPC
calls; previously, even simplest programs would make dozens of fully
redundant gsync_wake () calls.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20210915171110.226187-3-bugaevc@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
The next commit is going to introduce a new implementation of
THREAD_GSCOPE_WAIT which needs to access the list of threads.
Since it must be usable from the dynamic laoder, we have to move
the symbols for the list of threads into the loader.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20210915171110.226187-2-bugaevc@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
This patch adds the narrowing square root functions from TS 18661-1 /
TS 18661-3 / C2X to glibc's libm: fsqrt, fsqrtl, dsqrtl, f32sqrtf64,
f32sqrtf32x, f32xsqrtf64 for all configurations; f32sqrtf64x,
f32sqrtf128, f64sqrtf64x, f64sqrtf128, f32xsqrtf64x, f32xsqrtf128,
f64xsqrtf128 for configurations with _Float64x and _Float128;
__f32sqrtieee128 and __f64sqrtieee128 aliases in the powerpc64le case
(for calls to fsqrtl and dsqrtl when long double is IEEE binary128).
Corresponding tgmath.h macro support is also added.
The changes are mostly similar to those for the other narrowing
functions previously added, so the description of those generally
applies to this patch as well. However, the not-actually-narrowing
cases (where the two types involved in the function have the same
floating-point format) are aliased to sqrt, sqrtl or sqrtf128 rather
than needing a separately built not-actually-narrowing function such
as was needed for add / sub / mul / div. Thus, there is no
__nldbl_dsqrtl name for ldbl-opt because no such name was needed
(whereas the other functions needed such a name since the only other
name for that entry point was e.g. f32xaddf64, not reserved by TS
18661-1); the headers are made to arrange for sqrt to be called in
that case instead.
The DIAG_* calls in sysdeps/ieee754/soft-fp/s_dsqrtl.c are because
they were observed to be needed in GCC 7 testing of
riscv32-linux-gnu-rv32imac-ilp32. The other sysdeps/ieee754/soft-fp/
files added didn't need such DIAG_* in any configuration I tested with
build-many-glibcs.py, but if they do turn out to be needed in more
files with some other configuration / GCC version, they can always be
added there.
I reused the same test inputs in auto-libm-test-in as for
non-narrowing sqrt rather than adding extra or separate inputs for
narrowing sqrt. The tests in libm-test-narrow-sqrt.inc also follow
those for non-narrowing sqrt.
Tested as followed: natively with the full glibc testsuite for x86_64
(GCC 11, 7, 6) and x86 (GCC 11); with build-many-glibcs.py with GCC
11, 7 and 6; cross testing of math/ tests for powerpc64le, powerpc32
hard float, mips64 (all three ABIs, both hard and soft float). The
different GCC versions are to cover the different cases in tgmath.h
and tgmath.h tests properly (GCC 6 has _Float* only as typedefs in
glibc headers, GCC 7 has proper _Float* support, GCC 8 adds
__builtin_tgmath).
We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date. Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.
Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions. These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.
The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively. These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:
https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dchttps://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Gnumach's 0650a4ee30e3 implements support for high bits being set in the
mask parameter of vm_map. This allows to remove the fmh kludge that was
masking away the address range by mapping a dumb area there.
When the memory object is read-only, the kernel would be right in
refusing max vmprot containing VM_PROT_WRITE.
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
These deprecated functions are only safe to call from
__malloc_initialize_hook and as a result, are not useful in the
general case. Move the implementations to libc_malloc_debug so that
existing binaries that need it will now have to preload the debug DSO
to work correctly.
This also allows simplification of the core malloc implementation by
dropping all the undumping support code that was added to make
malloc_set_state work.
One known breakage is that of ancient emacs binaries that depend on
this. They will now crash when running with this libc. With
LD_BIND_NOW=1, it will terminate immediately because of not being able
to find malloc_set_state but with lazy binding it will crash in
unpredictable ways. It will need a preloaded libc_malloc_debug.so so
that its initialization hook is executed to allow its malloc
implementation to work properly.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
The malloc-check debugging feature is tightly integrated into glibc
malloc, so thanks to an idea from Florian Weimer, much of the malloc
implementation has been moved into libc_malloc_debug.so to support
malloc-check. Due to this, glibc malloc and malloc-check can no
longer work together; they use altogether different (but identical)
structures for heap management. This should not make a difference
though since the malloc check hook is not disabled anywhere.
malloc_set_state does, but it does so early enough that it shouldn't
cause any problems.
The malloc check tunable is now in the debug DSO and has no effect
when the DSO is not preloaded.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Wean mtrace away from the malloc hooks and move them into the debug
DSO. Split the API away from the implementation so that we can add
the API to libc.so as well as libc_malloc_debug.so, with the libc
implementations being empty.
Update localplt data since memalign no longer has any callers after
this change.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Split the mcheck implementation into the debugging hooks and API so
that the API can be replicated in libc and libc_malloc_debug.so. The
libc APIs always result in failure.
The mcheck implementation has also been moved entirely into
libc_malloc_debug.so and with it, all of the hook initialization code
can now be moved into the debug library. Now the initialization can
be done independently of libc internals.
With this patch, libc_malloc_debug.so can no longer be used with older
libcs, which is not its goal anyway. tst-vfork3 breaks due to this
since it spawns shell scripts, which in turn execute using the system
glibc. Move the test to tests-container so that only the built glibc
is used.
This move also fixes bugs in the mcheck version of memalign and
realloc, thus allowing removal of the tests from tests-mcheck
exclusion list.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Remove all malloc hook uses from core malloc functions and move it
into a new library libc_malloc_debug.so. With this, the hooks now no
longer have any effect on the core library.
libc_malloc_debug.so is a malloc interposer that needs to be preloaded
to get hooks functionality back so that the debugging features that
depend on the hooks, i.e. malloc-check, mcheck and mtrace work again.
Without the preloaded DSO these debugging features will be nops.
These features will be ported away from hooks in subsequent patches.
Similarly, legacy applications that need hooks functionality need to
preload libc_malloc_debug.so.
The symbols exported by libc_malloc_debug.so are maintained at exactly
the same version as libc.so.
Finally, static binaries will no longer be able to use malloc
debugging features since they cannot preload the debugging DSO.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This switches to public symbols without __ prefixes, due to improved
namespace management in glibc.
The script was used with --no-new-version to move the symbols
__res_nquery, __res_nquerydomain, __res_nsearch, __res_query,
__res_querydomain, __res_search, res_query, res_querydomain,
res_search. The public symbols res_nquery, res_nquerydomain,
res_nsearch, res_ownok, res_query, res_querydomain, res_search
were added with make update-all-abi.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This switches to public symbols without __ prefixes, due to improved
namespace management in glibc.
The symbols res_mkquery, __res_mkquery, __res_nmkquery were
moved with the script (using --no-new-version).
res_mkquery@@GLIBC_2.34, res_nmkquery@@GLIBC_2.34 were added using
make update-all-abi.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Switch to public symbols without __ prefix (due to improved
namespace management).
__res_send, __res_nsend were moved using the script (with
--no-new-version). res_send@@GLIBC_2.34 and res_nsend@@GLIBC_2.34
were added using make update-all-abi.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This reflects what the remaining functions in the file do.
The __res_dnok, __res_hnok, __res_mailok, __res_ownok were moved
with the script, using --no-new-version, and turned into compat
symbols. __libc_res_dnok@@GLIBC_PRIVATE and
__libc_res_hnok@@GLIBC_PRIVATE are added for internal use, to avoid
accidentally binding to compatibility symbols. The new public
symbols res_dnok, res_hnok, res_mailok, res_ownok were added using
make update-all-abi.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat it to GNU style.
dn_skipname is used outside glibc, so do not deprecate it,
and export it as dn_skipname (not __dn_skipname). Due to internal
users, provide a __libc_dn_skipname alias, and keep __dn_skipname
as a pure compatibility symbol.
__dn_skipname@GLIBC_2.0 was moved using the script, and
dn_skipname@@GLIBC_2.34 was added using make update-all-abi.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat it to GNU style.
dn_comp is used in various programs, so keep it as a non-deprecated
symbol. Switch to dn_comp (not __dn_comp) for the ABI name. There
are no internal users, so interposition is not a problem.
The __dn_comp symbol was moved with scripts/move-symbol-to-libc.py
--no-new-version. dn_comp@@GLIBC_2.34 was added with
make update-all-abi.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat to GNU style.
This switches back to the dn_expand name for the ABI symbol and turns
__dn_expand into a compatibility symbol. With the improved namespace
management in current glibc, it is no longer necessary to use a
private namespace symbol. To avoid old code binding to a
GLIBC_PRIVATE symbol by accident, use __libc_dn_expand for the
internal symbol name.
The symbols dn_expand, __dnexpand were moved using
scripts/move-symbol-to-libc.py, followed by an adjustment to make
dn_expand the only GLIBC_2.34 symbol.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat to GNU style.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat to GNU style, and eliminate the labellen function.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat to GNU style, and eliminate the digits variable.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat to GNU style. Check for negative error returns
(instead of -1).
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And reformat to GNU style. Avoid out-of-bounds pointer arithmetic.
This also results in a fix of bug 28091 due to the additional packet
length checks.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Carlos O'Donell <carlos@systemhalted.org>
Reformat to GNU style. Avoid out-of-bounds buffer arithmetic.
Eliminate the labellen function.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
Reformat to GNU style. Avoid out-of-bounds pointer arithmetic
(e.g., use eom - dn < 2 instead of dn + 1 >= eom). Inline the
labellen function and fold the compression pointer check into
the length check (l >= 64). Assume ASCII encoding.
The symbol was moved using scripts/move-symbol-to-libc.py.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This was put in __libc_fork by c32c868ab8 ("posix: Add _Fork [BZ #4737]")
so we need to avoid locking them again in _Fork called by __libc_lock, otherwise
we deadlock.
This patch adds a way to close a range of file descriptors on
posix_spawn as a new file action. The API is similar to the one
provided by Solaris 11 [1], where the file action causes the all open
file descriptors greater than or equal to input on to be closed when
the new process is spawned.
The function posix_spawn_file_actions_addclosefrom_np is safe to be
implemented by iterating over /proc/self/fd, since the Linux spawni.c
helper process does not use CLONE_FILES, so its has own file descriptor
table and any failure (in /proc operation) aborts the process creation
and returns an error to the caller.
I am aware that this file action might be redundant to the current
approach of POSIX in promoting O_CLOEXEC in more interfaces. However
O_CLOEXEC is still not the default and for some specific usages, the
caller needs to close all possible file descriptors to avoid them
leaking. Some examples are CPython (discussed in BZ#10353) and OpenJDK
jspawnhelper [2] (where OpenJDK spawns a helper process to exactly
closes all file descriptors). Most likely any environment which calls
functions that might open file descriptor under the hood and aim to use
posix_spawn might face the same requirement.
Checked on x86_64-linux-gnu and i686-linux-gnu on kernel 5.11 and 4.15.
[1] https://docs.oracle.com/cd/E36784_01/html/E36874/posix-spawn-file-actions-addclosefrom-np-3c.html
[2] https://github.com/openjdk/jdk/blob/master/src/java.base/unix/native/libjava/childproc.c#L82
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
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 Linux nptl implementation is used as base for generic fork
implementation to handle the internal locks and mutexes. The
system specific bits are moved a new internal _Fork symbol.
(This new implementation will be used to provide a async-signal-safe
_Fork now that POSIX has clarified that fork might not be
async-signal-safe [1]).
For Hurd it means that the __nss_database_fork_prepare_parent and
__nss_database_fork_subprocess will be run in a slight different
order.
[1] https://austingroupbugs.net/view.php?id=62
