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
This patch adds several new tunables to control the behavior of
elision on supported platforms[1]. Since elision now depends
on tunables, we should always *compile* with elision enabled,
and leave the code disabled, but available for runtime
selection. This gives us *much* better compile-time testing of
the existing code to avoid bit-rot[2].
Tested on ppc, ppc64, ppc64le, s390x and x86_64.
[1] This part of the patch was initially proposed by
Paul Murphy but was "staled" because the framework have changed
since the patch was originally proposed:
https://patchwork.sourceware.org/patch/10342/
[2] This part of the patch was inititally proposed as a RFC by
Carlos O'Donnell. Make sense to me integrate this on the patch:
https://sourceware.org/ml/libc-alpha/2017-05/msg00335.html
* elf/dl-tunables.list: Add elision parameters.
* manual/tunables.texi: Add entries about elision tunable.
* sysdeps/unix/sysv/linux/powerpc/elision-conf.c:
Add callback functions to dynamically enable/disable elision.
Add multiple callbacks functions to set elision parameters.
Deleted __libc_enable_secure check.
* sysdeps/unix/sysv/linux/s390/elision-conf.c: Likewise.
* sysdeps/unix/sysv/linux/x86/elision-conf.c: Likewise.
* configure: Regenerated.
* configure.ac: Option enable_lock_elision was deleted.
* config.h.in: ENABLE_LOCK_ELISION flag was deleted.
* config.make.in: Remove references to enable_lock_elision.
* manual/install.texi: Elision configure option was removed.
* INSTALL: Regenerated to remove enable_lock_elision.
* nptl/Makefile:
Disable elision so it can verify error case for destroying a mutex.
* sysdeps/powerpc/nptl/elide.h:
Cleanup ENABLE_LOCK_ELISION check.
Deleted macros for the case when ENABLE_LOCK_ELISION was not defined.
* sysdeps/s390/configure: Regenerated.
* sysdeps/s390/configure.ac: Remove references to enable_lock_elision..
* nptl/tst-mutex8.c:
Deleted all #ifndef ENABLE_LOCK_ELISION from the test.
* sysdeps/powerpc/powerpc32/sysdep.h:
Deleted all ENABLE_LOCK_ELISION checks.
* sysdeps/powerpc/powerpc64/sysdep.h: Likewise.
* sysdeps/powerpc/sysdep.h: Likewise.
* sysdeps/s390/nptl/bits/pthreadtypes-arch.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/force-elision.h: Likewise.
* sysdeps/unix/sysv/linux/s390/elision-conf.h: Likewise.
* sysdeps/unix/sysv/linux/s390/force-elision.h: Likewise.
* sysdeps/unix/sysv/linux/s390/lowlevellock.h: Likewise.
* sysdeps/unix/sysv/linux/s390/Makefile: Remove references to
enable-lock-elision.
Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
