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[PATCH] Use generic lowlevellock-futex.h in x86_64 lowlevellock.h.
- From: Torvald Riegel <triegel at redhat dot com>
- To: GLIBC Devel <libc-alpha at sourceware dot org>
- Date: Thu, 18 Dec 2014 00:15:57 +0100
- Subject: [PATCH] Use generic lowlevellock-futex.h in x86_64 lowlevellock.h.
- Authentication-results: sourceware.org; auth=none
This patch replaces the custom futex operations for x86_64 with the
generic ones from lowlevellock-futex.h. It also adds a few
#ifdef __ASSEMBLER__ to the generic Linux one to make this work.
In the long term, we'd want to use the fully generic low-level lock
implementation on x86_64 too, but this would require more code
inspection and/or measurements to assess the impacts on performance of
such a change.
Furthermore, there is still x86_64 assembly code that uses futexes, and
we need some of the futex macros (e.g., SYS_futex) be defined somewhere
for those assembly files. Thus, it seems easier to remove the
lowlevellock.h ones the other assembly uses of futexes have been
replaced with C code.
OK?
2014-12-17 Torvald Riegel <triegel@redhat.com>
* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Include
<lowlevellock-futex.h>. Remove FUTEX_* constants defined there.
(__lll_private_flag): Remove.
(lll_futex_wait): Likewise.
(lll_futex_timed_wait): Likewise.
(lll_futex_wake): Likewise.
(lll_futex_requeue): Likewise.
(lll_wait_tid): Use lll_futex_wait instead of assembly code.
(__lll_timedwait_tid): Spell out argument names.
(lll_timedwait_tid): Add comments and parentheses around macro
arguments.
* sysdeps/unix/sysv/linux/lowlevellock-futex.h: Make FUTEX_* constants,
LLL_SHARED and LLL_PRIVATE usable from assembly code.
commit dd87a779e2b9c80e24352f503a982d18969f4a90
Author: Torvald Riegel <triegel@redhat.com>
Date: Wed Dec 17 18:55:19 2014 +0100
Use generic lowlevellock-futex.h in x86_64 lowlevellock.h.
diff --git a/sysdeps/unix/sysv/linux/lowlevellock-futex.h b/sysdeps/unix/sysv/linux/lowlevellock-futex.h
index 8927661..907b4c7 100644
--- a/sysdeps/unix/sysv/linux/lowlevellock-futex.h
+++ b/sysdeps/unix/sysv/linux/lowlevellock-futex.h
@@ -19,10 +19,11 @@
#ifndef _LOWLEVELLOCK_FUTEX_H
#define _LOWLEVELLOCK_FUTEX_H 1
+#ifndef __ASSEMBLER__
#include <sysdep.h>
#include <tls.h>
#include <kernel-features.h>
-
+#endif
#define FUTEX_WAIT 0
#define FUTEX_WAKE 1
@@ -48,6 +49,7 @@
#define LLL_PRIVATE 0
#define LLL_SHARED FUTEX_PRIVATE_FLAG
+#ifndef __ASSEMBLER__
#if IS_IN (libc) || IS_IN (rtld)
/* In libc.so or ld.so all futexes are private. */
@@ -133,5 +135,6 @@
private), \
nr_wake, nr_move, mutex, val)
+#endif /* !__ASSEMBLER__ */
#endif /* lowlevellock-futex.h */
diff --git a/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h b/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
index 2f0cf5c..56570ee 100644
--- a/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
+++ b/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
@@ -45,59 +45,13 @@
# endif
#endif
+#include <lowlevellock-futex.h>
+
+/* XXX Remove when no assembler code uses futexes anymore. */
#define SYS_futex __NR_futex
-#define FUTEX_WAIT 0
-#define FUTEX_WAKE 1
-#define FUTEX_CMP_REQUEUE 4
-#define FUTEX_WAKE_OP 5
-#define FUTEX_LOCK_PI 6
-#define FUTEX_UNLOCK_PI 7
-#define FUTEX_TRYLOCK_PI 8
-#define FUTEX_WAIT_BITSET 9
-#define FUTEX_WAKE_BITSET 10
-#define FUTEX_WAIT_REQUEUE_PI 11
-#define FUTEX_CMP_REQUEUE_PI 12
-#define FUTEX_PRIVATE_FLAG 128
-#define FUTEX_CLOCK_REALTIME 256
-
-#define FUTEX_BITSET_MATCH_ANY 0xffffffff
-
-#define FUTEX_OP_CLEAR_WAKE_IF_GT_ONE ((4 << 24) | 1)
-
-/* Values for 'private' parameter of locking macros. Yes, the
- definition seems to be backwards. But it is not. The bit will be
- reversed before passing to the system call. */
-#define LLL_PRIVATE 0
-#define LLL_SHARED FUTEX_PRIVATE_FLAG
#ifndef __ASSEMBLER__
-#if IS_IN (libc) || IS_IN (rtld)
-/* In libc.so or ld.so all futexes are private. */
-# ifdef __ASSUME_PRIVATE_FUTEX
-# define __lll_private_flag(fl, private) \
- ((fl) | FUTEX_PRIVATE_FLAG)
-# else
-# define __lll_private_flag(fl, private) \
- ((fl) | THREAD_GETMEM (THREAD_SELF, header.private_futex))
-# endif
-#else
-# ifdef __ASSUME_PRIVATE_FUTEX
-# define __lll_private_flag(fl, private) \
- (((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
-# else
-# define __lll_private_flag(fl, private) \
- (__builtin_constant_p (private) \
- ? ((private) == 0 \
- ? ((fl) | THREAD_GETMEM (THREAD_SELF, header.private_futex)) \
- : (fl)) \
- : ({ unsigned int __fl = ((private) ^ FUTEX_PRIVATE_FLAG); \
- asm ("andl %%fs:%P1, %0" : "+r" (__fl) \
- : "i" (offsetof (struct pthread, header.private_futex))); \
- __fl | (fl); }))
-# endif
-#endif
-
/* Initializer for lock. */
#define LLL_LOCK_INITIALIZER (0)
#define LLL_LOCK_INITIALIZER_LOCKED (1)
@@ -106,39 +60,6 @@
/* Delay in spinlock loop. */
#define BUSY_WAIT_NOP asm ("rep; nop")
-#define lll_futex_wait(futex, val, private) \
- lll_futex_timed_wait(futex, val, NULL, private)
-
-
-#define lll_futex_timed_wait(futex, val, timeout, private) \
- ({ \
- register const struct timespec *__to __asm ("r10") = timeout; \
- int __status; \
- register __typeof (val) _val __asm ("edx") = (val); \
- __asm __volatile ("syscall" \
- : "=a" (__status) \
- : "0" (SYS_futex), "D" (futex), \
- "S" (__lll_private_flag (FUTEX_WAIT, private)), \
- "d" (_val), "r" (__to) \
- : "memory", "cc", "r11", "cx"); \
- __status; \
- })
-
-
-#define lll_futex_wake(futex, nr, private) \
- ({ \
- int __status; \
- register __typeof (nr) _nr __asm ("edx") = (nr); \
- LIBC_PROBE (lll_futex_wake, 3, futex, nr, private); \
- __asm __volatile ("syscall" \
- : "=a" (__status) \
- : "0" (SYS_futex), "D" (futex), \
- "S" (__lll_private_flag (FUTEX_WAKE, private)), \
- "d" (_nr) \
- : "memory", "cc", "r10", "r11", "cx"); \
- __status; \
- })
-
/* NB: in the lll_trylock macro we simply return the value in %eax
after the cmpxchg instruction. In case the operation succeded this
@@ -378,58 +299,38 @@ extern int __lll_timedlock_elision (int *futex, short *adapt_count,
} \
while (0)
-/* Returns non-zero if error happened, zero if success. */
-#define lll_futex_requeue(ftx, nr_wake, nr_move, mutex, val, private) \
- ({ int __res; \
- register int __nr_move __asm ("r10") = nr_move; \
- register void *__mutex __asm ("r8") = mutex; \
- register int __val __asm ("r9") = val; \
- __asm __volatile ("syscall" \
- : "=a" (__res) \
- : "0" (__NR_futex), "D" ((void *) ftx), \
- "S" (__lll_private_flag (FUTEX_CMP_REQUEUE, \
- private)), "d" (nr_wake), \
- "r" (__nr_move), "r" (__mutex), "r" (__val) \
- : "cx", "r11", "cc", "memory"); \
- __res < 0; })
-
#define lll_islocked(futex) \
(futex != LLL_LOCK_INITIALIZER)
/* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex
- wakeup when the clone terminates. The memory location contains the
- thread ID while the clone is running and is reset to zero
- afterwards.
-
- The macro parameter must not have any side effect. */
+ wake-up when the clone terminates. The memory location contains the
+ thread ID while the clone is running and is reset to zero by the kernel
+ afterwards. The kernel up to version 3.16.3 does not use the private futex
+ operations for futex wake-up when the clone terminates. */
#define lll_wait_tid(tid) \
- do { \
- int __ignore; \
- register __typeof (tid) _tid asm ("edx") = (tid); \
- if (_tid != 0) \
- __asm __volatile ("xorq %%r10, %%r10\n\t" \
- "1:\tmovq %2, %%rax\n\t" \
- "syscall\n\t" \
- "cmpl $0, (%%rdi)\n\t" \
- "jne 1b" \
- : "=&a" (__ignore) \
- : "S" (FUTEX_WAIT), "i" (SYS_futex), "D" (&tid), \
- "d" (_tid) \
- : "memory", "cc", "r10", "r11", "cx"); \
+ do { \
+ __typeof (tid) __tid; \
+ while ((__tid = (tid)) != 0) \
+ lll_futex_wait (&(tid), __tid, LLL_SHARED);\
} while (0)
-extern int __lll_timedwait_tid (int *tid, const struct timespec *abstime)
+extern int __lll_timedwait_tid (int *, const struct timespec *)
attribute_hidden;
+
+/* As lll_wait_tid, but with a timeout. If the timeout occurs then return
+ ETIMEDOUT. If ABSTIME is invalid, return EINVAL.
+ XXX Note that this differs from the generic version in that we do the
+ error checking here and not in __lll_timedwait_tid. */
#define lll_timedwait_tid(tid, abstime) \
({ \
int __result = 0; \
- if (tid != 0) \
+ if ((tid) != 0) \
{ \
- if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) \
+ if ((abstime)->tv_nsec < 0 || (abstime)->tv_nsec >= 1000000000) \
__result = EINVAL; \
else \
- __result = __lll_timedwait_tid (&tid, abstime); \
+ __result = __lll_timedwait_tid (&(tid), (abstime)); \
} \
__result; })