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f0458cf4f9
Linux from 3.9 through 4.2 does not abort HTM transaction on syscalls, instead it suspend and resume it when leaving the kernel. The side-effects of the syscall will always remain visible, even if the transaction is aborted. This is an issue when transaction is used along with futex syscall, on pthread_cond_wait for instance, where the futex call might succeed but the transaction is rolled back leading the pthread_cond object in an inconsistent state. Glibc used to prevent it by always aborting a transaction before issuing a syscall. Linux 4.2 also decided to abort active transaction in syscalls which makes the glibc workaround superfluous. Worse, glibc transaction abortion leads to a performance issue on recent kernels where the HTM state is saved/restore lazily (v4.9). By aborting a transaction on every syscalls, regardless whether a transaction has being initiated before, GLIBS makes the kernel always save/restore HTM state (it can not even lazily disable it after a certain number of syscall iterations). Because of this shortcoming, Transactional Lock Elision is just enabled when it has been explicitly set (either by tunables of by a configure switch) and if kernel aborts HTM transactions on syscalls (PPC_FEATURE2_HTM_NOSC). It is reported that using simple benchmark [1], the context-switch is about 5% faster by not issuing a tabort in every syscall in newer kernels. Checked on powerpc64le-linux-gnu with 4.4.0 kernel (Ubuntu 16.04). * NEWS: Add note about new TLE support on powerpc64le. * sysdeps/powerpc/nptl/tcb-offsets.sym (TM_CAPABLE): Remove. * sysdeps/powerpc/nptl/tls.h (tcbhead_t): Rename tm_capable to __ununsed1. (TLS_INIT_TP, TLS_DEFINE_INIT_TP): Remove tm_capable setup. (THREAD_GET_TM_CAPABLE, THREAD_SET_TM_CAPABLE): Remove macros. * sysdeps/powerpc/powerpc32/sysdep.h, sysdeps/powerpc/powerpc64/sysdep.h (ABORT_TRANSACTION_IMPL, ABORT_TRANSACTION): Remove macros. * sysdeps/powerpc/sysdep.h (ABORT_TRANSACTION): Likewise. * sysdeps/unix/sysv/linux/powerpc/elision-conf.c (elision_init): Set __pthread_force_elision iff PPC_FEATURE2_HTM_NOSC is set. * sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h, sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h sysdeps/unix/sysv/linux/powerpc/syscall.S (ABORT_TRANSACTION): Remove usage. * sysdeps/unix/sysv/linux/powerpc/not-errno.h: Remove file. Reported-by: Breno Leitão <leitao@debian.org>
161 lines
4.5 KiB
C
161 lines
4.5 KiB
C
/* Assembly macros for 32-bit PowerPC.
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Copyright (C) 1999-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <sysdeps/powerpc/sysdep.h>
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#ifdef __ASSEMBLER__
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/* If compiled for profiling, call `_mcount' at the start of each
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function. */
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#ifdef PROF
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/* The mcount code relies on a the return address being on the stack
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to locate our caller and so it can restore it; so store one just
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for its benefit. */
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# define CALL_MCOUNT \
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mflr r0; \
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stw r0,4(r1); \
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cfi_offset (lr, 4); \
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bl JUMPTARGET(_mcount);
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#else /* PROF */
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# define CALL_MCOUNT /* Do nothing. */
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#endif /* PROF */
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#define ENTRY(name) \
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.globl C_SYMBOL_NAME(name); \
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.type C_SYMBOL_NAME(name),@function; \
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.align ALIGNARG(2); \
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C_LABEL(name) \
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cfi_startproc; \
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CALL_MCOUNT
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#define ENTRY_TOCLESS(name) ENTRY(name)
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/* helper macro for accessing the 32-bit powerpc GOT. */
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#define SETUP_GOT_ACCESS(regname,GOT_LABEL) \
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bcl 20,31,GOT_LABEL ; \
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GOT_LABEL: ; \
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mflr (regname)
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#define EALIGN_W_0 /* No words to insert. */
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#define EALIGN_W_1 nop
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#define EALIGN_W_2 nop;nop
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#define EALIGN_W_3 nop;nop;nop
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#define EALIGN_W_4 EALIGN_W_3;nop
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#define EALIGN_W_5 EALIGN_W_4;nop
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#define EALIGN_W_6 EALIGN_W_5;nop
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#define EALIGN_W_7 EALIGN_W_6;nop
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/* EALIGN is like ENTRY, but does alignment to 'words'*4 bytes
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past a 2^align boundary. */
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#ifdef PROF
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# define EALIGN(name, alignt, words) \
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.globl C_SYMBOL_NAME(name); \
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.type C_SYMBOL_NAME(name),@function; \
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.align ALIGNARG(2); \
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C_LABEL(name) \
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cfi_startproc; \
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CALL_MCOUNT \
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b 0f; \
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.align ALIGNARG(alignt); \
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EALIGN_W_##words; \
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0:
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#else /* PROF */
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# define EALIGN(name, alignt, words) \
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.globl C_SYMBOL_NAME(name); \
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.type C_SYMBOL_NAME(name),@function; \
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.align ALIGNARG(alignt); \
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EALIGN_W_##words; \
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C_LABEL(name) \
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cfi_startproc;
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#endif
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#undef END
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#define END(name) \
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cfi_endproc; \
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ASM_SIZE_DIRECTIVE(name)
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#define DO_CALL(syscall) \
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li 0,syscall; \
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sc
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#undef JUMPTARGET
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#ifdef PIC
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# define JUMPTARGET(name) name##@plt
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#else
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# define JUMPTARGET(name) name
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#endif
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#if defined SHARED && defined PIC && !defined NO_HIDDEN
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# undef HIDDEN_JUMPTARGET
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# define HIDDEN_JUMPTARGET(name) __GI_##name##@local
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#endif
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#define PSEUDO(name, syscall_name, args) \
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.section ".text"; \
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ENTRY (name) \
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DO_CALL (SYS_ify (syscall_name));
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#define PSEUDO_RET \
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bnslr+; \
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b __syscall_error@local
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#define ret PSEUDO_RET
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#undef PSEUDO_END
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#define PSEUDO_END(name) \
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END (name)
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#define PSEUDO_NOERRNO(name, syscall_name, args) \
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.section ".text"; \
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ENTRY (name) \
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DO_CALL (SYS_ify (syscall_name));
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#define PSEUDO_RET_NOERRNO \
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blr
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#define ret_NOERRNO PSEUDO_RET_NOERRNO
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#undef PSEUDO_END_NOERRNO
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#define PSEUDO_END_NOERRNO(name) \
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END (name)
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#define PSEUDO_ERRVAL(name, syscall_name, args) \
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.section ".text"; \
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ENTRY (name) \
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DO_CALL (SYS_ify (syscall_name));
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#define PSEUDO_RET_ERRVAL \
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blr
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#define ret_ERRVAL PSEUDO_RET_ERRVAL
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#undef PSEUDO_END_ERRVAL
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#define PSEUDO_END_ERRVAL(name) \
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END (name)
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/* Local labels stripped out by the linker. */
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#undef L
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#define L(x) .L##x
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#define XGLUE(a,b) a##b
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#define GLUE(a,b) XGLUE (a,b)
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#define GENERATE_GOT_LABEL(name) GLUE (.got_label, name)
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/* Label in text section. */
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#define C_TEXT(name) name
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#endif /* __ASSEMBLER__ */
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