The elision interfaces are closely aligned between the targets that
implement them, so declare them in the generic <lowlevellock.h>
file.
Empty .c stubs are provided, so that fewer makefile updates
under sysdeps are needed. Also simplify initialization via
__libc_early_init.
The symbols __lll_clocklock_elision, __lll_lock_elision,
__lll_trylock_elision, __lll_unlock_elision, __pthread_force_elision
move into libc. For the time being, non-hidden references are used
from libpthread to access them, but once that part of libpthread
is moved into libc, hidden symbols will be used again. (Hidden
references seem desirable to reduce the likelihood of transactions
aborts.)
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
The pthread_mutex_clocklock and pthread_mutex_timedlock have been converted
to support 64 bit time.
This change uses:
- New __futex_clocklock_wait64 (instead of lll_timedwait)
from ./sysdeps/nptl/futex-helpers.c and
- New __futex_clocklock64 function (instead of lll_clocklock)
- New futex_lock_pi64
defined in sysdeps/nptl/futex-internal.h
The pthread_mutex_{clock|timed}lock only accepts absolute time.
Moreover, there is no need to check for NULL passed as *abstime pointer to the
syscalls as those calls have exported symbols marked with __nonull attribute
for abstime.
Some architectures - namely x86, powerpc and s390 - do support lock elision.
For those - adjustments have been made in arch specific elision-*.c files
to use __futex_clocklock64 instead of lll_clocklock.
The __lll_lock_elision (aliased to __lll_clocklock_elision in e.g.
sysdeps/unix/sysv/linux/s390/elision-timed.c) just uses, in this patch
provided, __futex_clocklock64.
For systems with __TIMESIZE != 64 && __WORDSIZE == 32:
- Conversions between 64 bit time to 32 bit are necessary
- Redirection to pthread_mutex_{clock|timed}lock will provide support for 64
bit time
Build tests:
./src/scripts/build-many-glibcs.py glibcs
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Rename lll_timedlock to lll_clocklock and add clockid
parameter to indicate the clock that the abstime parameter should
be measured against in preparation for adding
pthread_mutex_clocklock.
The name change mirrors the naming for the exposed pthread functions:
timed => absolute timeout measured against CLOCK_REALTIME (or clock
specified by attribute in the case of pthread_cond_timedwait.)
clock => absolute timeout measured against clock specified in preceding
parameter.
* sysdeps/nptl/lowlevellock.h (lll_clocklock): Rename from
lll_timedlock and add clockid parameter. (__lll_clocklock): Rename
from __lll_timedlock and add clockid parameter.
* sysdeps/unix/sysv/linux/sparc/lowlevellock.h (lll_clocklock):
Likewise.
* nptl/lll_timedlock_wait.c (__lll_clocklock_wait): Rename from
__lll_timedlock_wait and add clockid parameter. Use __clock_gettime
rather than __gettimeofday so that clockid can be used. This means
that conversion from struct timeval is no longer required.
* sysdeps/sparc/sparc32/lowlevellock.c (lll_clocklock_wait):
Likewise.
* sysdeps/sparc/sparc32/lll_timedlock_wait.c: Update comment to
refer to __lll_clocklock_wait rather than __lll_timedlock_wait.
* nptl/pthread_mutex_timedlock.c (lll_clocklock_elision): Rename
from lll_timedlock_elision, add clockid parameter and use
meaningful names for other parameters. (__pthread_mutex_timedlock):
Pass CLOCK_REALTIME where necessary to lll_clocklock and
lll_clocklock_elision.
* sysdeps/unix/sysv/linux/powerpc/lowlevellock.h
(lll_clocklock_elision): Rename from lll_timedlock_elision and add
clockid parameter. (__lll_clocklock_elision): Rename from
__lll_timedlock_elision and add clockid parameter.
* sysdeps/unix/sysv/linux/s390/lowlevellock.h: Likewise.
* sysdeps/unix/sysv/linux/x86/lowlevellock.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/elision-timed.c
(__lll_lock_elision): Call __lll_clocklock_elision rather than
__lll_timedlock_elision. (EXTRAARG): Add clockid parameter.
(LLL_LOCK): Likewise.
* sysdeps/unix/sysv/linux/s390/elision-timed.c: Likewise.
* sysdeps/unix/sysv/linux/x86/elision-timed.c: Likewise.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This patch removes the arch-specific x86 assembly implementation for
low level locking and consolidate both 64 bits and 32 bits in a
single implementation.
Different than other architectures, x86 lll_trylock, lll_lock, and
lll_unlock implements a single-thread optimization to avoid atomic
operation, using cmpxchgl instead. This patch implements by using
the new single-thread.h definitions in a generic way, although using
the previous semantic.
The lll_cond_trylock, lll_cond_lock, and lll_timedlock just use
atomic operations plus calls to lll_lock_wait*.
For __lll_lock_wait_private and __lll_lock_wait the generic implemtation
there is no indication that assembly implementation is required
performance-wise.
Checked on x86_64-linux-gnu and i686-linux-gnu.
* sysdeps/nptl/lowlevellock.h (__lll_trylock): New macro.
(lll_trylock): Call __lll_trylock.
* sysdeps/unix/sysv/linux/i386/libc-lowlevellock.S: Remove file.
* sysdeps/unix/sysv/linux/i386/lll_timedlock_wait.c: Likewise.
* sysdeps/unix/sysv/linux/i386/lowlevellock.S: Likewise.
* sysdeps/unix/sysv/linux/i386/lowlevellock.h: Likewise.
* sysdeps/unix/sysv/linux/x86_64/libc-lowlevellock.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/lll_timedlock_wait.c: Likewise.
* sysdeps/unix/sysv/linux/x86_64/lowlevellock.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Likewise.
* sysdeps/unix/sysv/linux/x86/lowlevellock.h: New file.
* sysdeps/unix/sysv/linux/x86_64/cancellation.S: Include
lowlevellock-futex.h.
Florian Weimer
Paul Eggert
Lukasz Majewski
Joseph Myers
Mike Crowe
Adhemerval Zanella