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Author SHA1 Message Date
Stefan Liebler
12d2dd7060 Optimize generic spinlock code and use C11 like atomic macros. 
This patch optimizes the generic spinlock code.

The type pthread_spinlock_t is a typedef to volatile int on all archs.
Passing a volatile pointer to the atomic macros which are not mapped to the
C11 atomic builtins can lead to extra stores and loads to stack if such
a macro creates a temporary variable by using "__typeof (*(mem)) tmp;".
Thus, those macros which are used by spinlock code - atomic_exchange_acquire,
atomic_load_relaxed, atomic_compare_exchange_weak - have to be adjusted.
According to the comment from  Szabolcs Nagy, the type of a cast expression is
unqualified (see http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_423.htm):
__typeof ((__typeof (*(mem)) *(mem)) tmp;
Thus from spinlock perspective the variable tmp is of type int instead of
type volatile int.  This patch adjusts those macros in include/atomic.h.
With this construct GCC >= 5 omits the extra stores and loads.

The atomic macros are replaced by the C11 like atomic macros and thus
the code is aligned to it.  The pthread_spin_unlock implementation is now
using release memory order instead of sequentially consistent memory order.
The issue with passed volatile int pointers applies to the C11 like atomic
macros as well as the ones used before.

I've added a glibc_likely hint to the first atomic exchange in
pthread_spin_lock in order to return immediately to the caller if the lock is
free.  Without the hint, there is an additional jump if the lock is free.

I've added the atomic_spin_nop macro within the loop of plain reads.
The plain reads are also realized by C11 like atomic_load_relaxed macro.

The new define ATOMIC_EXCHANGE_USES_CAS determines if the first try to acquire
the spinlock in pthread_spin_lock or pthread_spin_trylock is an exchange
or a CAS.  This is defined in atomic-machine.h for all architectures.

The define SPIN_LOCK_READS_BETWEEN_CMPXCHG is now removed.
There is no technical reason for throwing in a CAS every now and then,
and so far we have no evidence that it can improve performance.
If that would be the case, we have to adjust other spin-waiting loops
elsewhere, too!  Using a CAS loop without plain reads is not a good idea
on many targets and wasn't used by one.  Thus there is now no option to
do so.

Architectures are now using the generic spinlock automatically if they
do not provide an own implementation.  Thus the pthread_spin_lock.c files
in sysdeps folder are deleted.

ChangeLog:

	* NEWS: Mention new spinlock implementation.
	* include/atomic.h:
	(__atomic_val_bysize): Cast type to omit volatile qualifier.
	(atomic_exchange_acq): Likewise.
	(atomic_load_relaxed): Likewise.
	(ATOMIC_EXCHANGE_USES_CAS): Check definition.
	* nptl/pthread_spin_init.c (pthread_spin_init):
	Use atomic_store_relaxed.
	* nptl/pthread_spin_lock.c (pthread_spin_lock):
	Use C11-like atomic macros.
	* nptl/pthread_spin_trylock.c (pthread_spin_trylock):
	Likewise.
	* nptl/pthread_spin_unlock.c (pthread_spin_unlock):
	Use atomic_store_release.
	* sysdeps/aarch64/nptl/pthread_spin_lock.c: Delete File.
	* sysdeps/arm/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/hppa/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/m68k/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/microblaze/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/mips/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/nios2/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/aarch64/atomic-machine.h (ATOMIC_EXCHANGE_USES_CAS): Define.
	* sysdeps/alpha/atomic-machine.h: Likewise.
	* sysdeps/arm/atomic-machine.h: Likewise.
	* sysdeps/i386/atomic-machine.h: Likewise.
	* sysdeps/ia64/atomic-machine.h: Likewise.
	* sysdeps/m68k/coldfire/atomic-machine.h: Likewise.
	* sysdeps/m68k/m680x0/m68020/atomic-machine.h: Likewise.
	* sysdeps/microblaze/atomic-machine.h: Likewise.
	* sysdeps/mips/atomic-machine.h: Likewise.
	* sysdeps/powerpc/powerpc32/atomic-machine.h: Likewise.
	* sysdeps/powerpc/powerpc64/atomic-machine.h: Likewise.
	* sysdeps/s390/atomic-machine.h: Likewise.
	* sysdeps/sparc/sparc32/atomic-machine.h: Likewise.
	* sysdeps/sparc/sparc32/sparcv9/atomic-machine.h: Likewise.
	* sysdeps/sparc/sparc64/atomic-machine.h: Likewise.
	* sysdeps/tile/tilegx/atomic-machine.h: Likewise.
	* sysdeps/tile/tilepro/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/hppa/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/m68k/coldfire/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/nios2/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/sh/atomic-machine.h: Likewise.
	* sysdeps/x86_64/atomic-machine.h: Likewise.
 2017-06-06 09:41:56 +02:00
Zack Weinberg
9090848d06 Narrowing the visibility of libc-internal.h even further. 
posix/wordexp-test.c used libc-internal.h for PTR_ALIGN_DOWN; similar
to what was done with libc-diag.h, I have split the definitions of
cast_to_integer, ALIGN_UP, ALIGN_DOWN, PTR_ALIGN_UP, and PTR_ALIGN_DOWN
to a new header, libc-pointer-arith.h.

It then occurred to me that the remaining declarations in libc-internal.h
are mostly to do with early initialization, and probably most of the
files including it, even in the core code, don't need it anymore.  Indeed,
only 19 files actually need what remains of libc-internal.h.  23 others
need libc-diag.h instead, and 12 need libc-pointer-arith.h instead.
No file needs more than one of them, and 16 don't need any of them!

So, with this patch, libc-internal.h stops including libc-diag.h as
well as losing the pointer arithmetic macros, and all including files
are adjusted.

        * include/libc-pointer-arith.h: New file.  Define
	cast_to_integer, ALIGN_UP, ALIGN_DOWN, PTR_ALIGN_UP, and
        PTR_ALIGN_DOWN here.
        * include/libc-internal.h: Definitions of above macros
	moved from here.  Don't include libc-diag.h anymore either.
	* posix/wordexp-test.c: Include stdint.h and libc-pointer-arith.h.
        Don't include libc-internal.h.

	* debug/pcprofile.c, elf/dl-tunables.c, elf/soinit.c, io/openat.c
	* io/openat64.c, misc/ptrace.c, nptl/pthread_clock_gettime.c
	* nptl/pthread_clock_settime.c, nptl/pthread_cond_common.c
	* string/strcoll_l.c, sysdeps/nacl/brk.c
	* sysdeps/unix/clock_settime.c
	* sysdeps/unix/sysv/linux/i386/get_clockfreq.c
	* sysdeps/unix/sysv/linux/ia64/get_clockfreq.c
	* sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c
	* sysdeps/unix/sysv/linux/sparc/sparc64/get_clockfreq.c:
	Don't include libc-internal.h.

	* elf/get-dynamic-info.h, iconv/loop.c
	* iconvdata/iso-2022-cn-ext.c, locale/weight.h, locale/weightwc.h
	* misc/reboot.c, nis/nis_table.c, nptl_db/thread_dbP.h
	* nscd/connections.c, resolv/res_send.c, soft-fp/fmadf4.c
	* soft-fp/fmasf4.c, soft-fp/fmatf4.c, stdio-common/vfscanf.c
	* sysdeps/ieee754/dbl-64/e_lgamma_r.c
	* sysdeps/ieee754/dbl-64/k_rem_pio2.c
	* sysdeps/ieee754/flt-32/e_lgammaf_r.c
	* sysdeps/ieee754/flt-32/k_rem_pio2f.c
	* sysdeps/ieee754/ldbl-128/k_tanl.c
	* sysdeps/ieee754/ldbl-128ibm/k_tanl.c
	* sysdeps/ieee754/ldbl-96/e_lgammal_r.c
	* sysdeps/ieee754/ldbl-96/k_tanl.c, sysdeps/nptl/futex-internal.h:
	Include libc-diag.h instead of libc-internal.h.

        * elf/dl-load.c, elf/dl-reloc.c, locale/programs/locarchive.c
        * nptl/nptl-init.c, string/strcspn.c, string/strspn.c
	* malloc/malloc.c, sysdeps/i386/nptl/tls.h
	* sysdeps/nacl/dl-map-segments.h, sysdeps/x86_64/atomic-machine.h
	* sysdeps/unix/sysv/linux/spawni.c
        * sysdeps/x86_64/nptl/tls.h:
        Include libc-pointer-arith.h instead of libc-internal.h.

	* elf/get-dynamic-info.h, sysdeps/nacl/dl-map-segments.h
	* sysdeps/x86_64/atomic-machine.h:
        Add multiple include guard.
 2017-03-01 20:33:46 -05:00
Joseph Myers
bfff8b1bec Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
Joseph Myers
f7a9f785e5 Update copyright dates with scripts/update-copyrights. 2016-01-04 16:05:18 +00:00
Joseph Myers
9f9f27248b Remove miscellaneous GCC >= 4.7 version conditionals. 
This patch removes miscellaneous __GNUC_PREREQ (4, 7) conditionals
that are now dead.

Tested for x86_64 and x86 (testsuite, and that installed stripped
shared libraries are unchanged by the patch).

	* sysdeps/arm/atomic-machine.h
	[__GNUC_PREREQ (4, 7) && __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4]:
	Change conditional to [__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4].
	[__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 && !__GNUC_PREREQ (4, 7)]:
	Remove conditional code.
	[!__GNUC_PREREQ (4, 7) || !__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4]:
	Change conditional to [!__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4].
	* sysdeps/i386/sysdep.h [__ASSEMBLER__ && __GNUC_PREREQ (4, 7)]:
	Change conditional to [__ASSEMBLER__].
	[__ASSEMBLER__ && !__GNUC_PREREQ (4, 7)]: Remove conditional code.
	[!__ASSEMBLER__ && __GNUC_PREREQ (4, 7)]: Change conditional to
	[!__ASSEMBLER__].
	[!__ASSEMBLER__ && !__GNUC_PREREQ (4, 7)]: Remove conditional
	code.
	* sysdeps/unix/sysv/linux/sh/atomic-machine.h (rNOSP): Remove
	conditional macro definitions.
	(__arch_compare_and_exchange_val_8_acq): Use "u" instead of rNOSP.
	(__arch_compare_and_exchange_val_16_acq): Likewise.
	(__arch_compare_and_exchange_val_32_acq): Likewise.
	(atomic_exchange_and_add): Likewise.
	(atomic_add): Likewise.
	(atomic_add_negative): Likewise.
	(atomic_add_zero): Likewise.
	(atomic_bit_set): Likewise.
	(atomic_bit_test_set): Likewise.
	* sysdeps/x86_64/atomic-machine.h [__GNUC_PREREQ (4, 7)]: Make
	code unconditional.
	[!__GNUC_PREREQ (4, 7)]: Remove conditional code.
 2015-11-04 21:34:36 +00:00
Joseph Myers
de071d199a Move bits/atomic.h to atomic-machine.h (bug 14912). 
It was noted in
<https://sourceware.org/ml/libc-alpha/2012-09/msg00305.html> that the
bits/*.h naming scheme should only be used for installed headers.
This patch renames bits/atomic.h to atomic-machine.h to follow that
convention.

This is the only change in this series that needs to change the
filename rather than simply removing a directory level (because both
atomic.h and bits/atomic.h exist at present).

Tested for x86_64 (testsuite, and that installed stripped shared
libraries are unchanged by the patch).

	[BZ #14912]
	* sysdeps/aarch64/bits/atomic.h: Move to ...
	* sysdeps/aarch64/atomic-machine.h: ...here.
	(_AARCH64_BITS_ATOMIC_H): Rename macro to
	_AARCH64_ATOMIC_MACHINE_H.
	* sysdeps/alpha/bits/atomic.h: Move to ...
	* sysdeps/alpha/atomic-machine.h: ...here.
	* sysdeps/arm/bits/atomic.h: Move to ...
	* sysdeps/arm/atomic-machine.h: ...here.  Update comments.
	* bits/atomic.h: Move to ...
	* sysdeps/generic/atomic-machine.h: ...here.
	(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
	* sysdeps/i386/bits/atomic.h: Move to ...
	* sysdeps/i386/atomic-machine.h: ...here.
	* sysdeps/ia64/bits/atomic.h: Move to ...
	* sysdeps/ia64/atomic-machine.h: ...here.
	* sysdeps/m68k/coldfire/bits/atomic.h: Move to ...
	* sysdeps/m68k/coldfire/atomic-machine.h: ...here.
	(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
	* sysdeps/m68k/m680x0/m68020/bits/atomic.h: Move to ...
	* sysdeps/m68k/m680x0/m68020/atomic-machine.h: ...here.
	* sysdeps/microblaze/bits/atomic.h: Move to ...
	* sysdeps/microblaze/atomic-machine.h: ...here.
	* sysdeps/mips/bits/atomic.h: Move to ...
	* sysdeps/mips/atomic-machine.h: ...here.
	(_MIPS_BITS_ATOMIC_H): Rename macro to _MIPS_ATOMIC_MACHINE_H.
	* sysdeps/powerpc/bits/atomic.h: Move to ...
	* sysdeps/powerpc/atomic-machine.h: ...here.  Update comments.
	* sysdeps/powerpc/powerpc32/bits/atomic.h: Move to ...
	* sysdeps/powerpc/powerpc32/atomic-machine.h: ...here.  Update
	comments.  Include <atomic-machine.h> instead of <bits/atomic.h>.
	* sysdeps/powerpc/powerpc64/bits/atomic.h: Move to ...
	* sysdeps/powerpc/powerpc64/atomic-machine.h: ...here.  Include
	<atomic-machine.h> instead of <bits/atomic.h>.
	* sysdeps/s390/bits/atomic.h: Move to ...
	* sysdeps/s390/atomic-machine.h: ...here.
	* sysdeps/sparc/sparc32/bits/atomic.h: Move to ...
	* sysdeps/sparc/sparc32/atomic-machine.h: ...here.
	(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
	* sysdeps/sparc/sparc32/sparcv9/bits/atomic.h: Move to ...
	* sysdeps/sparc/sparc32/sparcv9/atomic-machine.h: ...here.
	* sysdeps/sparc/sparc64/bits/atomic.h: Move to ...
	* sysdeps/sparc/sparc64/atomic-machine.h: ...here.
	* sysdeps/tile/bits/atomic.h: Move to ...
	* sysdeps/tile/atomic-machine.h: ...here.
	* sysdeps/tile/tilegx/bits/atomic.h: Move to ...
	* sysdeps/tile/tilegx/atomic-machine.h: ...here.  Include
	<sysdeps/tile/atomic-machine.h> instead of
	<sysdeps/tile/bits/atomic.h>.
	(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
	* sysdeps/tile/tilepro/bits/atomic.h: Move to ...
	* sysdeps/tile/tilepro/atomic-machine.h: ...here.  Include
	<sysdeps/tile/atomic-machine.h> instead of
	<sysdeps/tile/bits/atomic.h>.
	(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
	* sysdeps/unix/sysv/linux/arm/bits/atomic.h: Move to ...
	* sysdeps/unix/sysv/linux/arm/atomic-machine.h: ...here.  Include
	<sysdeps/arm/atomic-machine.h> instead of
	<sysdeps/arm/bits/atomic.h>.
	* sysdeps/unix/sysv/linux/hppa/bits/atomic.h: Move to ...
	* sysdeps/unix/sysv/linux/hppa/atomic-machine.h: ...here.
	(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
	* sysdeps/unix/sysv/linux/m68k/coldfire/bits/atomic.h: Move to ...
	* sysdeps/unix/sysv/linux/m68k/coldfire/atomic-machine.h: ...here.
	(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
	* sysdeps/unix/sysv/linux/nios2/bits/atomic.h: Move to ...
	* sysdeps/unix/sysv/linux/nios2/atomic-machine.h: ...here.
	(_NIOS2_BITS_ATOMIC_H): Rename macro to _NIOS2_ATOMIC_MACHINE_H.
	* sysdeps/unix/sysv/linux/sh/bits/atomic.h: Move to ...
	* sysdeps/unix/sysv/linux/sh/atomic-machine.h: ...here.
	* sysdeps/x86_64/bits/atomic.h: Move to ...
	* sysdeps/x86_64/atomic-machine.h: ...here.
	* include/atomic.h: Include <atomic-machine.h> instead of
	<bits/atomic.h>.
 2015-09-11 20:00:19 +00:00