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This replaces the pthread rwlock with a new implementation that uses a
more scalable algorithm (primarily through not using a critical section
anymore to make state changes). The fast path for rdlock acquisition and
release is now basically a single atomic read-modify write or CAS and a few
branches. See nptl/pthread_rwlock_common.c for details.
* nptl/DESIGN-rwlock.txt: Remove.
* nptl/lowlevelrwlock.sym: Remove.
* nptl/Makefile: Add new tests.
* nptl/pthread_rwlock_common.c: New file. Contains the new rwlock.
* nptl/pthreadP.h (PTHREAD_RWLOCK_PREFER_READER_P): Remove.
(PTHREAD_RWLOCK_WRPHASE, PTHREAD_RWLOCK_WRLOCKED,
PTHREAD_RWLOCK_RWAITING, PTHREAD_RWLOCK_READER_SHIFT,
PTHREAD_RWLOCK_READER_OVERFLOW, PTHREAD_RWLOCK_WRHANDOVER,
PTHREAD_RWLOCK_FUTEX_USED): New.
* nptl/pthread_rwlock_init.c (__pthread_rwlock_init): Adapt to new
implementation.
* nptl/pthread_rwlock_rdlock.c (__pthread_rwlock_rdlock_slow): Remove.
(__pthread_rwlock_rdlock): Adapt.
* nptl/pthread_rwlock_timedrdlock.c
(pthread_rwlock_timedrdlock): Adapt.
* nptl/pthread_rwlock_timedwrlock.c
(pthread_rwlock_timedwrlock): Adapt.
* nptl/pthread_rwlock_trywrlock.c (pthread_rwlock_trywrlock): Adapt.
* nptl/pthread_rwlock_tryrdlock.c (pthread_rwlock_tryrdlock): Adapt.
* nptl/pthread_rwlock_unlock.c (pthread_rwlock_unlock): Adapt.
* nptl/pthread_rwlock_wrlock.c (__pthread_rwlock_wrlock_slow): Remove.
(__pthread_rwlock_wrlock): Adapt.
* nptl/tst-rwlock10.c: Adapt.
* nptl/tst-rwlock11.c: Adapt.
* nptl/tst-rwlock17.c: New file.
* nptl/tst-rwlock18.c: New file.
* nptl/tst-rwlock19.c: New file.
* nptl/tst-rwlock2b.c: New file.
* nptl/tst-rwlock8.c: Adapt.
* nptl/tst-rwlock9.c: Adapt.
* sysdeps/aarch64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/arm/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/hppa/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/ia64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/m68k/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/microblaze/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/mips/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/nios2/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/s390/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/sh/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/sparc/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/tile/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h
(pthread_rwlock_t): Adapt.
* sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h
(pthread_rwlock_t): Adapt.
* sysdeps/x86/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
* nptl/nptl-printers.py (): Adapt.
* nptl/nptl_lock_constants.pysym: Adapt.
* nptl/test-rwlock-printers.py: Adapt.
* nptl/test-rwlockattr-printers.c: Adapt.
* nptl/test-rwlockattr-printers.py: Adapt.
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This corresponds to a patch applied to libgcc. In glibc it doesn't
actually affect much (only fma, I think).
The MIPS sfp-machine.h files have an _FP_CHOOSENAN implementation
which emulates hardware semantics of not preserving signaling NaN
payloads for an operation with two NaN arguments (although that
doesn't suffice to avoid sNaN payload preservation in any case with
just one NaN argument).
However, those are only hardware semantics in the legacy NaN case; in
the NAN2008 case, the architecture documentation says hardware
preserves payloads in such cases. Furthermore, this implementation
assumes legacy NaN semantics, so in the NAN2008 case the
implementation actually has the effect of preserving sNaN payloads but
not preserving qNaN payloads, when both should be preserved.
This patch fixes the code just to copy from the first argument.
Tested for mips64 soft-float.
* sysdeps/mips/mips32/sfp-machine.h (_FP_CHOOSENAN): Always
preserve NaN payload if [__mips_nan2008].
* sysdeps/mips/mips64/sfp-machine.h (_FP_CHOOSENAN): Likewise.
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Testing for MIPS soft float shows that the issue with NaN payload
preservation applies to soft float as well as hard float: the
sfp-machine.h emulates hardware non-preservation semantics, although
only for the case of two NaN arguments.
This patch duly changes the MIPS math-tests.h to expect such
non-preservation for soft float as well as hard float. The issue in
the NAN2008 case for which I posted
<https://gcc.gnu.org/ml/gcc-patches/2017-01/msg00034.html>, of sNaN
payloads being preserved but qNaN payloads not being preserved, is not
currently an issue for glibc tests because we don't have any tests
that check for qNaN payloads being preserved by arithmetic, so a
simple __mips_nan2008 conditional suffices without needing compiler
version checks in the __mips_nan2008 case.
Tested for mips64 soft float.
* sysdeps/mips/math-tests.h (SNAN_TESTS_PRESERVE_PAYLOAD): Do not
condition on [__mips_hard_float].
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This is a new implementation for condition variables, required
after http://austingroupbugs.net/view.php?id=609 to fix bug 13165. In
essence, we need to be stricter in which waiters a signal or broadcast
is required to wake up; this couldn't be solved using the old algorithm.
ISO C++ made a similar clarification, so this also fixes a bug in
current libstdc++, for example.
We can't use the old algorithm anymore because futexes do not guarantee
to wake in FIFO order. Thus, when we wake, we can't simply let any
waiter grab a signal, but we need to ensure that one of the waiters
happening before the signal is woken up. This is something the previous
algorithm violated (see bug 13165).
There's another issue specific to condvars: ABA issues on the underlying
futexes. Unlike mutexes that have just three states, or semaphores that
have no tokens or a limited number of them, the state of a condvar is
the *order* of the waiters. A waiter on a semaphore can grab a token
whenever one is available; a condvar waiter must only consume a signal
if it is eligible to do so as determined by the relative order of the
waiter and the signal.
Therefore, this new algorithm maintains two groups of waiters: Those
eligible to consume signals (G1), and those that have to wait until
previous waiters have consumed signals (G2). Once G1 is empty, G2
becomes the new G1. 64b counters are used to avoid ABA issues.
This condvar doesn't yet use a requeue optimization (ie, on a broadcast,
waking just one thread and requeueing all others on the futex of the
mutex supplied by the program). I don't think doing the requeue is
necessarily the right approach (but I haven't done real measurements
yet):
* If a program expects to wake many threads at the same time and make
that scalable, a condvar isn't great anyway because of how it requires
waiters to operate mutually exclusive (due to the mutex usage). Thus, a
thundering herd problem is a scalability problem with or without the
optimization. Using something like a semaphore might be more
appropriate in such a case.
* The scalability problem is actually at the mutex side; the condvar
could help (and it tries to with the requeue optimization), but it
should be the mutex who decides how that is done, and whether it is done
at all.
* Forcing all but one waiter into the kernel-side wait queue of the
mutex prevents/avoids the use of lock elision on the mutex. Thus, it
prevents the only cure against the underlying scalability problem
inherent to condvars.
* If condvars use short critical sections (ie, hold the mutex just to
check a binary flag or such), which they should do ideally, then forcing
all those waiter to proceed serially with kernel-based hand-off (ie,
futex ops in the mutex' contended state, via the futex wait queues) will
be less efficient than just letting a scalable mutex implementation take
care of it. Our current mutex impl doesn't employ spinning at all, but
if critical sections are short, spinning can be much better.
* Doing the requeue stuff requires all waiters to always drive the mutex
into the contended state. This leads to each waiter having to call
futex_wake after lock release, even if this wouldn't be necessary.
[BZ #13165]
* nptl/pthread_cond_broadcast.c (__pthread_cond_broadcast): Rewrite to
use new algorithm.
* nptl/pthread_cond_destroy.c (__pthread_cond_destroy): Likewise.
* nptl/pthread_cond_init.c (__pthread_cond_init): Likewise.
* nptl/pthread_cond_signal.c (__pthread_cond_signal): Likewise.
* nptl/pthread_cond_wait.c (__pthread_cond_wait): Likewise.
(__pthread_cond_timedwait): Move here from pthread_cond_timedwait.c.
(__condvar_confirm_wakeup, __condvar_cancel_waiting,
__condvar_cleanup_waiting, __condvar_dec_grefs,
__pthread_cond_wait_common): New.
(__condvar_cleanup): Remove.
* npt/pthread_condattr_getclock.c (pthread_condattr_getclock): Adapt.
* npt/pthread_condattr_setclock.c (pthread_condattr_setclock):
Likewise.
* npt/pthread_condattr_getpshared.c (pthread_condattr_getpshared):
Likewise.
* npt/pthread_condattr_init.c (pthread_condattr_init): Likewise.
* nptl/tst-cond1.c: Add comment.
* nptl/tst-cond20.c (do_test): Adapt.
* nptl/tst-cond22.c (do_test): Likewise.
* sysdeps/aarch64/nptl/bits/pthreadtypes.h (pthread_cond_t): Adapt
structure.
* sysdeps/arm/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/ia64/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/m68k/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/microblaze/nptl/bits/pthreadtypes.h (pthread_cond_t):
Likewise.
* sysdeps/mips/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/nios2/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/s390/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/sh/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/tile/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h (pthread_cond_t):
Likewise.
* sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h (pthread_cond_t):
Likewise.
* sysdeps/x86/bits/pthreadtypes.h (pthread_cond_t): Likewise.
* sysdeps/nptl/internaltypes.h (COND_NWAITERS_SHIFT): Remove.
(COND_CLOCK_BITS): Adapt.
* sysdeps/nptl/pthread.h (PTHREAD_COND_INITIALIZER): Adapt.
* nptl/pthreadP.h (__PTHREAD_COND_CLOCK_MONOTONIC_MASK,
__PTHREAD_COND_SHARED_MASK): New.
* nptl/nptl-printers.py (CLOCK_IDS): Remove.
(ConditionVariablePrinter, ConditionVariableAttributesPrinter): Adapt.
* nptl/nptl_lock_constants.pysym: Adapt.
* nptl/test-cond-printers.py: Adapt.
* sysdeps/unix/sysv/linux/hppa/internaltypes.h (cond_compat_clear,
cond_compat_check_and_clear): Adapt.
* sysdeps/unix/sysv/linux/hppa/pthread_cond_timedwait.c: Remove file ...
* sysdeps/unix/sysv/linux/hppa/pthread_cond_wait.c
(__pthread_cond_timedwait): ... and move here.
* nptl/DESIGN-condvar.txt: Remove file.
* nptl/lowlevelcond.sym: Likewise.
* nptl/pthread_cond_timedwait.c: Likewise.
* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_broadcast.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_signal.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_broadcast.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_signal.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_timedwait.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_wait.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_broadcast.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_signal.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_timedwait.S: Likewise.
* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_wait.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/pthread_cond_broadcast.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/pthread_cond_signal.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S: Likewise.
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Information about whether the ABI of long double is the same as that
of double is split between bits/mathdef.h and bits/wordsize.h.
When the ABIs are the same, bits/mathdef.h defines
__NO_LONG_DOUBLE_MATH. In addition, in the case where the same glibc
binary supports both -mlong-double-64 and -mlong-double-128,
bits/wordsize.h defines __LONG_DOUBLE_MATH_OPTIONAL, along with
__NO_LONG_DOUBLE_MATH if this particular compilation is with
-mlong-double-64.
As part of the refactoring I proposed in
<https://sourceware.org/ml/libc-alpha/2016-11/msg00745.html>, this
patch puts all that information in a single header,
bits/long-double.h. It is included from sys/cdefs.h alongside the
include of bits/wordsize.h, so other headers generally do not need to
include bits/long-double.h directly.
Previously, various bits/mathdef.h headers and bits/wordsize.h headers
had this long double information (including implicitly in some
bits/mathdef.h headers through not having the defines present in the
default version). After the patch, it's all in six bits/long-double.h
headers. Furthermore, most of those new headers are not
architecture-specific. Architectures with optional long double all
use the ldbl-opt sysdeps directory, either in the order (ldbl-64-128,
ldbl-opt, ldbl-128) or (ldbl-128ibm, ldbl-opt). Thus a generic header
for the case where long double = double, and headers in ldbl-128,
ldbl-96 and ldbl-opt, suffices to cover every architecture except for
cases where long double properties vary between different ABIs sharing
a set of installed headers; fortunately all the ldbl-opt cases share a
single compiler-predefined macro __LONG_DOUBLE_128__ that can be used
to tell whether this compilation is -mlong-double-64 or
-mlong-double-128.
The two cases where a set of headers is shared between ABIs with
different long double properties, MIPS (o32 has long double = double,
other ABIs use ldbl-128) and SPARC (32-bit has optional long double,
64-bit has required long double), need their own bits/long-double.h
headers.
As with bits/wordsize.h, multiple-include protection for this header
is generally implicit through the include guards on sys/cdefs.h, and
multiple inclusion is harmless in any case. There is one subtlety:
the header must not define __LONG_DOUBLE_MATH_OPTIONAL if
__NO_LONG_DOUBLE_MATH was defined before its inclusion, because doing
so breaks how sysdeps/ieee754/ldbl-opt/nldbl-compat.h defines
__NO_LONG_DOUBLE_MATH itself before including system headers. Subject
to keeping that working, it would be reasonable to move these macros
from defined/undefined #ifdef to always-defined 1/0 #if semantics, but
this patch does not attempt to do so, just rearranges where the macros
are defined.
After this patch, the only use of bits/mathdef.h is the alpha one for
modifying complex function ABIs for old GCC. Thus, all versions of
the header other than the default and alpha versions are removed, as
is the include from math.h.
Tested for x86_64 and x86. Also did compilation-only testing with
build-many-glibcs.py.
* bits/long-double.h: New file.
* sysdeps/ieee754/ldbl-128/bits/long-double.h: Likewise.
* sysdeps/ieee754/ldbl-96/bits/long-double.h: Likewise.
* sysdeps/ieee754/ldbl-opt/bits/long-double.h: Likewise.
* sysdeps/mips/bits/long-double.h: Likewise.
* sysdeps/unix/sysv/linux/sparc/bits/long-double.h: Likewise.
* math/Makefile (headers): Add bits/long-double.h.
* misc/sys/cdefs.h: Include <bits/long-double.h>.
* stdlib/strtold.c: Include <bits/long-double.h> instead of
<bits/wordsize.h>.
* bits/mathdef.h [!_COMPLEX_H]: Do not allow inclusion.
[!__NO_LONG_DOUBLE_MATH]: Remove conditional code.
* math/math.h: Do not include <bits/mathdef.h>.
* sysdeps/aarch64/bits/mathdef.h: Remove file.
* sysdeps/alpha/bits/mathdef.h [!_COMPLEX_H]: Do not allow
inclusion.
* sysdeps/ia64/bits/mathdef.h: Remove file.
* sysdeps/m68k/m680x0/bits/mathdef.h: Likewise.
* sysdeps/mips/bits/mathdef.h: Likewise.
* sysdeps/powerpc/bits/mathdef.h: Likewise.
* sysdeps/s390/bits/mathdef.h: Likewise.
* sysdeps/sparc/bits/mathdef.h: Likewise.
* sysdeps/x86/bits/mathdef.h: Likewise.
* sysdeps/s390/s390-32/bits/wordsize.h
[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]: Remove
conditional code.
* sysdeps/s390/s390-64/bits/wordsize.h
[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
Likewise.
* sysdeps/unix/sysv/linux/alpha/bits/wordsize.h
[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
Likewise.
* sysdeps/unix/sysv/linux/powerpc/bits/wordsize.h
[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
Likewise.
* sysdeps/unix/sysv/linux/sparc/bits/wordsize.h
[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
Likewise.
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This patch adds the missing hidden_def (__sigsetjmp) on various
architectures that were failing to build (as noted in
<https://sourceware.org/ml/libc-alpha/2016-11/msg01124.html>).
Tested (compilation only) with build-many-glibcs.py.
* sysdeps/alpha/setjmp.S (__sigsetjmp): Use hidden_def.
* sysdeps/hppa/setjmp.S (__sigsetjmp): Likewise.
* sysdeps/mips/mips64/setjmp.S (__sigsetjmp): Likewise.
* sysdeps/mips/setjmp.S (__sigsetjmp): Likewise.
* sysdeps/sh/sh3/setjmp.S (__sigsetjmp): Likewise.
* sysdeps/sh/sh4/setjmp.S (__sigsetjmp): Likewise.
* sysdeps/sparc/sparc32/setjmp.S (__sigsetjmp): Likewise.
* sysdeps/tile/setjmp.S (__sigsetjmp): Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/setjmp.S (__sigsetjmp):
Likewise.
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Continuing the refactoring of bits/mathdef.h, this patch stops it
defining FP_ILOGB0 and FP_ILOGBNAN, moving the required information to
a new header bits/fp-logb.h.
There are only two possible values of each of those macros permitted
by ISO C. TS 18661-1 adds corresponding macros for llogb, and their
values are required to correspond to those of the ilogb macros in the
obvious way. Thus two boolean values - for which the same choices are
correct for most architectures - suffice to determine the value of all
these macros, and by defining macros for those boolean values in
bits/fp-logb.h we can then define the public FP_* macros in math.h and
avoid the present duplication of the associated feature test macro
logic.
This patch duly moves to bits/fp-logb.h defining __FP_LOGB0_IS_MIN and
__FP_LOGBNAN_IS_MIN. Default definitions of those to 0 are correct
for both architectures, while ia64, m68k and x86 get their own
versions of bits/fp-logb.h to reflect their use of values different
from the defaults.
The patch renders many copies of bits/mathdef.h trivial (needed only
to avoid the default __NO_LONG_DOUBLE_MATH). I'll revise
<https://sourceware.org/ml/libc-alpha/2016-11/msg00865.html>
accordingly so that it removes all bits/mathdef.h headers except the
default one and the alpha one, and arranges for the header to be
included only by complex.h as the only remaining use at that point
will be for the alpha ABI issues there.
Tested for x86_64 and x86. Also did compile-only testing with
build-many-glibcs.py (using glibc sources from before the commit that
introduced many build failures with undefined __GI___sigsetjmp).
* bits/fp-logb.h: New file.
* sysdeps/ia64/bits/fp-logb.h: Likewise.
* sysdeps/m68k/m680x0/bits/fp-logb.h: Likewise.
* sysdeps/x86/bits/fp-logb.h: Likewise.
* math/Makefile (headers): Add bits/fp-logb.h.
* math/math.h: Include <bits/fp-logb.h>.
[__USE_ISOC99] (FP_ILOGB0): Define based on __FP_LOGB0_IS_MIN.
[__USE_ISOC99] (FP_ILOGBNAN): Define based on __FP_LOGBNAN_IS_MIN.
* bits/mathdef.h (FP_ILOGB0): Remove.
(FP_ILOGBNAN): Likewise.
* sysdeps/aarch64/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/alpha/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/ia64/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/m68k/m680x0/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/mips/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/powerpc/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/s390/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/sparc/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
* sysdeps/x86/bits/mathdef.h (FP_ILOGB0): Likewise.
(FP_ILOGBNAN): Likewise.
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This patch remove the PID cache and usage in current GLIBC code. Current
usage is mainly used a performance optimization to avoid the syscall,
however it adds some issues:
- The exposed clone syscall will try to set pid/tid to make the new
thread somewhat compatible with current GLIBC assumptions. This cause
a set of issue with new workloads and usecases (such as BZ#17214 and
[1]) as well for new internal usage of clone to optimize other algorithms
(such as clone plus CLONE_VM for posix_spawn, BZ#19957).
- The caching complexity also added some bugs in the past [2] [3] and
requires more effort of each port to handle such requirements (for
both clone and vfork implementation).
- Caching performance gain in mainly on getpid and some specific
code paths. The getpid performance leverage is questionable [4],
either by the idea of getpid being a hotspot as for the getpid
implementation itself (if it is indeed a justifiable hotspot a
vDSO symbol could let to a much more simpler solution).
Other usage is mainly for non usual code paths, such as pthread
cancellation signal and handling.
For thread creation (on stack allocation) the code simplification in fact
adds some performance gain due the no need of transverse the stack cache
and invalidate each element pid.
Other thread usages will require a direct getpid syscall, such as
cancellation/setxid signal, thread cancellation, thread fail path (at
create_thread), and thread signal (pthread_kill and pthread_sigqueue).
However these are hardly usual hotspots and I think adding a syscall is
justifiable.
It also simplifies both the clone and vfork arch-specific implementation.
And by review each fork implementation there are some discrepancies that
this patch also solves:
- microblaze clone/vfork does not set/reset the pid/tid field
- hppa uses the default vfork implementation that fallback to fork.
Since vfork is deprecated I do not think we should bother with it.
The patch also removes the TID caching in clone. My understanding for
such semantic is try provide some pthread usage after a user program
issue clone directly (as done by thread creation with CLONE_PARENT_SETTID
and pthread tid member). However, as stated before in multiple discussions
threads, GLIBC provides clone syscalls without further supporting all this
semantics.
I ran a full make check on x86_64, x32, i686, armhf, aarch64, and powerpc64le.
For sparc32, sparc64, and mips I ran the basic fork and vfork tests from
posix/ folder (on a qemu system). So it would require further testing
on alpha, hppa, ia64, m68k, nios2, s390, sh, and tile (I excluded microblaze
because it is already implementing the patch semantic regarding clone/vfork).
[1] https://codereview.chromium.org/800183004/
[2] https://sourceware.org/ml/libc-alpha/2006-07/msg00123.html
[3] https://sourceware.org/bugzilla/show_bug.cgi?id=15368
[4] http://yarchive.net/comp/linux/getpid_caching.html
* sysdeps/nptl/fork.c (__libc_fork): Remove pid cache setting.
* nptl/allocatestack.c (allocate_stack): Likewise.
(__reclaim_stacks): Likewise.
(setxid_signal_thread): Obtain pid through syscall.
* nptl/nptl-init.c (sigcancel_handler): Likewise.
(sighandle_setxid): Likewise.
* nptl/pthread_cancel.c (pthread_cancel): Likewise.
* sysdeps/unix/sysv/linux/pthread_kill.c (__pthread_kill): Likewise.
* sysdeps/unix/sysv/linux/pthread_sigqueue.c (pthread_sigqueue):
Likewise.
* sysdeps/unix/sysv/linux/createthread.c (create_thread): Likewise.
* sysdeps/unix/sysv/linux/getpid.c: Remove file.
* nptl/descr.h (struct pthread): Change comment about pid value.
* nptl/pthread_getattr_np.c (pthread_getattr_np): Remove thread
pid assert.
* sysdeps/unix/sysv/linux/pthread-pids.h (__pthread_initialize_pids):
Do not set pid value.
* nptl_db/td_ta_thr_iter.c (iterate_thread_list): Remove thread
pid cache check.
* nptl_db/td_thr_validate.c (td_thr_validate): Likewise.
* sysdeps/aarch64/nptl/tcb-offsets.sym: Remove pid offset.
* sysdeps/alpha/nptl/tcb-offsets.sym: Likewise.
* sysdeps/arm/nptl/tcb-offsets.sym: Likewise.
* sysdeps/hppa/nptl/tcb-offsets.sym: Likewise.
* sysdeps/i386/nptl/tcb-offsets.sym: Likewise.
* sysdeps/ia64/nptl/tcb-offsets.sym: Likewise.
* sysdeps/m68k/nptl/tcb-offsets.sym: Likewise.
* sysdeps/microblaze/nptl/tcb-offsets.sym: Likewise.
* sysdeps/mips/nptl/tcb-offsets.sym: Likewise.
* sysdeps/nios2/nptl/tcb-offsets.sym: Likewise.
* sysdeps/powerpc/nptl/tcb-offsets.sym: Likewise.
* sysdeps/s390/nptl/tcb-offsets.sym: Likewise.
* sysdeps/sh/nptl/tcb-offsets.sym: Likewise.
* sysdeps/sparc/nptl/tcb-offsets.sym: Likewise.
* sysdeps/tile/nptl/tcb-offsets.sym: Likewise.
* sysdeps/x86_64/nptl/tcb-offsets.sym: Likewise.
* sysdeps/unix/sysv/linux/aarch64/clone.S: Remove pid and tid caching.
* sysdeps/unix/sysv/linux/alpha/clone.S: Likewise.
* sysdeps/unix/sysv/linux/arm/clone.S: Likewise.
* sysdeps/unix/sysv/linux/hppa/clone.S: Likewise.
* sysdeps/unix/sysv/linux/i386/clone.S: Likewise.
* sysdeps/unix/sysv/linux/ia64/clone2.S: Likewise.
* sysdeps/unix/sysv/linux/mips/clone.S: Likewise.
* sysdeps/unix/sysv/linux/nios2/clone.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sh/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/tile/clone.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/aarch64/vfork.S: Remove pid set and reset.
* sysdeps/unix/sysv/linux/alpha/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/arm/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/i386/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/ia64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/m68k/clone.S: Likewise.
* sysdeps/unix/sysv/linux/m68k/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/mips/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/nios2/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/sh/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/tile/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/tst-clone2.c (f): Remove direct pthread
struct access.
(clone_test): Remove function.
(do_test): Rewrite to take in consideration pid is not cached anymore.
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At present, definitions of float_t and double_t are split among many
bits/mathdef.h headers.
For all but three architectures, these types are float and double.
Furthermore, if you assume __FLT_EVAL_METHOD__ to be defined, that
provides a more generic way of determining the correct values of these
typedefs. Defining these typedefs more generally based on
__FLT_EVAL_METHOD__ was previously proposed by Paul Eggert in
<https://sourceware.org/ml/libc-alpha/2012-02/msg00002.html>.
This patch refactors things in the way I proposed in
<https://sourceware.org/ml/libc-alpha/2016-11/msg00745.html>. A new
header bits/flt-eval-method.h defines a single macro,
__GLIBC_FLT_EVAL_METHOD, which is then used by math.h to define
float_t and double_t. The default is based on __FLT_EVAL_METHOD__
(although actually a default to 0 would have the same effect for
current ports, because ports where values other than 0 or 16 are
possible all have their own headers).
To avoid changing the existing semantics in any case, including for
compilers not defining __FLT_EVAL_METHOD__, architecture-specific
files are then added for m68k, s390, x86 which replicate the existing
semantics. At least with __FLT_EVAL_METHOD__ values possible with
GCC, there should be no change to the choices of float_t and double_t
for any supported configuration.
Architecture maintainer notes:
* m68k: sysdeps/m68k/m680x0/bits/flt-eval-method.h always defines
__GLIBC_FLT_EVAL_METHOD to 2 to replicate the existing logic. But
actually GCC defines __FLT_EVAL_METHOD__ to 0 if TARGET_68040. It
might make sense to make the header prefer to base things on
__FLT_EVAL_METHOD__ if defined, like the x86 version, and so make
the choices of these types more accurate (with a NEWS entry as for
the other changes to these types on particular architectures).
* s390: sysdeps/s390/bits/flt-eval-method.h always defines
__GLIBC_FLT_EVAL_METHOD to 1 to replicate the existing logic. As
previously discussed, it might make sense in coordination with GCC
to eliminate the historic mistake, avoid excess precision in the
-fexcess-precision=standard case and make the typedefs match (with a
NEWS entry, again).
Tested for x86-64 and x86. Also did compilation-only testing with
build-many-glibcs.py.
* bits/flt-eval-method.h: New file.
* sysdeps/m68k/m680x0/bits/flt-eval-method.h: Likewise.
* sysdeps/s390/bits/flt-eval-method.h: Likewise.
* sysdeps/x86/bits/flt-eval-method.h: Likewise.
* math/Makefile (headers): Add bits/flt-eval-method.h.
* math/math.h: Include <bits/flt-eval-method.h>.
[__USE_ISOC99] (float_t): Define based on __GLIBC_FLT_EVAL_METHOD.
[__USE_ISOC99] (double_t): Likewise.
* bits/mathdef.h (float_t): Remove.
(double_t): Likewise.
* sysdeps/aarch64/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/alpha/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/arm/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/hppa/fpu/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/ia64/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/m68k/m680x0/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/mips/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/powerpc/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/s390/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/sh/sh4/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/sparc/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/tile/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
* sysdeps/x86/bits/mathdef.h (float_t): Likewise.
(double_t): Likewise.
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In a microMIPS compilation of `.init' code use the R_MICROMIPS_JALR
relocation intended for PIC call relaxation in microMIPS code rather
than the corresponding R_MIPS_JALR relocation meant for regular MIPS
code only.
* sysdeps/mips/mips32/crti.S (JALR_RELOC): New macro.
(_init): Use it in place of hardcoded R_MIPS_JALR.
* sysdeps/mips/mips64/n32/crti.S (JALR_RELOC): New macro.
(_init): Use it in place of hardcoded R_MIPS_JALR.
* sysdeps/mips/mips64/n64/crti.S (JALR_RELOC): New macro.
(_init): Use it in place of hardcoded R_MIPS_JALR.
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Avoid a build error with microMIPS compilation and recent versions of
GAS which complain if a branch targets a label which is marked as data
rather than microMIPS code:
../sysdeps/mips/mips32/crti.S: Assembler messages:
../sysdeps/mips/mips32/crti.S:72: Error: branch to a symbol in another ISA mode
make[2]: *** [.../csu/crti.o] Error 1
as commit 9d862524f6ae ("MIPS: Verify the ISA mode and alignment of
branch and jump targets") closed a hole in branch processing, making
relocation calculation respect the ISA mode of the symbol referred.
This allowed diagnosing the situation where an attempt is made to pass
control from code assembled for one ISA mode to code assembled for a
different ISA mode and either relaxing the branch to a cross-mode jump
or if that is not possible, then reporting this as an error rather than
letting such code build and then fail unpredictably at the run time.
This however requires the correct annotation of branch targets as code,
because the ISA mode is not relevant for data symbols and is therefore
not recorded for them. The `.insn' pseudo-op is used for this purpose
and has been supported by GAS since:
Wed Feb 12 14:36:29 1997 Ian Lance Taylor <ian@cygnus.com>
* config/tc-mips.c (mips_pseudo_table): Add "insn".
(s_insn): New static function.
* doc/c-mips.texi: Document .insn.
so there has been no reason to avoid it where required. More recently
this pseudo-op has been documented, by the microMIPS architecture
specification[1][2], as required for the correct interpretation of any
code label which is not followed by an actual instruction in an assembly
source.
Use it in our crti.S files then, to mark that the trailing label there
with no instructions following is indeed not a code bug and the branch
is legitimate.
References:
[1] "MIPS Architecture for Programmers, Volume II-B: The microMIPS32
Instruction Set", MIPS Technologies, Inc., Document Number: MD00582,
Revision 5.04, January 15, 2014, Section 7.1 "Assembly-Level
Compatibility", p. 533
[2] "MIPS Architecture for Programmers, Volume II-B: The microMIPS64
Instruction Set", MIPS Technologies, Inc., Document Number: MD00594,
Revision 5.04, January 15, 2014, Section 8.1 "Assembly-Level
Compatibility", p. 623
2016-11-18 Matthew Fortune <Matthew.Fortune@imgtec.com>
Maciej W. Rozycki <macro@imgtec.com>
* sysdeps/mips/mips32/crti.S (_init): Add `.insn' pseudo-op at
`.Lno_weak_fn' label.
* sysdeps/mips/mips64/n32/crti.S (_init): Likewise.
* sysdeps/mips/mips64/n64/crti.S (_init): Likewise.
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manual/libm-err-tab.pl hardcodes a list of names for particular
platforms (mapping from sysdeps directory name to friendly name for
the manual). This goes against the principle of keeping information
about individual platforms in their corresponding sysdeps directory,
and the list is also very out-of-date regarding supported platforms
and their corresponding sysdeps directories.
This patch fixes this by adding a libm-test-ulps-name file alongside
each libm-test-ulps file. The script then gets the friendly name from
that file, which is required to exist, so it no longer needs to allow
for the mapping being missing.
Tested for x86_64.
[BZ #14139]
* manual/libm-err-tab.pl (%pplatforms): Initialize to empty.
(find_files): Obtain platform name from libm-test-ulps-name and
store in %pplatforms.
(canonicalize_platform): Remove.
(print_platforms): Use $pplatforms directly.
(by_platforms): Do not allow for platforms missing from
%pplatforms.
* sysdeps/aarch64/libm-test-ulps-name: New file.
* sysdeps/alpha/fpu/libm-test-ulps-name: Likewise.
* sysdeps/arm/libm-test-ulps-name: Likewise.
* sysdeps/generic/libm-test-ulps-name: Likewise.
* sysdeps/hppa/fpu/libm-test-ulps-name: Likewise.
* sysdeps/i386/fpu/libm-test-ulps-name: Likewise.
* sysdeps/i386/i686/fpu/multiarch/libm-test-ulps-name: Likewise.
* sysdeps/ia64/fpu/libm-test-ulps-name: Likewise.
* sysdeps/m68k/coldfire/fpu/libm-test-ulps-name: Likewise.
* sysdeps/m68k/m680x0/fpu/libm-test-ulps-name: Likewise.
* sysdeps/microblaze/libm-test-ulps-name: Likewise.
* s |
