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aec5785e7b
The changes made in commitbc59e28bf6(issue #3399) fixed introspection of the GThread API. However, they introduced a trampoline in every threading function. So with those changes applied, the disassembly of `g_mutex_lock()` (for example) was: ``` 0x7ffff7f038b0 <g_mutex_lock> jmp 0x7ffff7f2f440 <g_mutex_lock_impl> 0x7ffff7f038b5 data16 cs nopw 0x0(%rax,%rax,1) ``` i.e. It jumps straight to the `_impl` function, even with an optimised build. Since `g_mutex_lock()` (and various other GThread functions) are frequently run hot paths, this additional `jmp` to a function which has ended up in a different code page is a slowdown which we’d rather avoid. So, this commit reworks things to define all the `_impl` functions as `G_ALWAYS_INLINE static inline` (which typically expands to `__attribute__((__always_inline__)) static inline`), and to move them into the same compilation unit as `gthread.c` so that they can be inlined without the need for link-time optimisation to be enabled. It makes the code a little less readable, but not much worse than what commitbc59e28bf6already did. And perhaps the addition of the `inline` decorations to all the `_impl` functions will make it a bit clearer what their intended purpose is (platform-specific implementations). After applying this commit, the disassembly of `g_mutex_lock()` successfully contains the inlining for me: ``` => 0x00007ffff7f03d80 <+0>: xor %eax,%eax 0x00007ffff7f03d82 <+2>: mov $0x1,%edx 0x00007ffff7f03d87 <+7>: lock cmpxchg %edx,(%rdi) 0x00007ffff7f03d8b <+11>: jne 0x7ffff7f03d8e <g_mutex_lock+14> 0x00007ffff7f03d8d <+13>: ret 0x00007ffff7f03d8e <+14>: jmp 0x7ffff7f03610 <g_mutex_lock_slowpath> ``` I considered making a similar change to the other APIs touched in #3399 (GContentType, GAppInfo, GSpawn), but they are all much less performance critical, so it’s probably not worth making their code more complex for that sake. Signed-off-by: Philip Withnall <pwithnall@gnome.org> Fixes: #3417
179 lines
8.8 KiB
C
179 lines
8.8 KiB
C
/* GLIB - Library of useful routines for C programming
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*
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* gthreadprivate.h - GLib internal thread system related declarations.
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*
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* Copyright (C) 2003 Sebastian Wilhelmi
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*
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* SPDX-License-Identifier: LGPL-2.1-or-later
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*
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* This 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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*
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* This 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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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __G_THREADPRIVATE_H__
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#define __G_THREADPRIVATE_H__
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#include "config.h"
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#include "deprecated/gthread.h"
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typedef struct _GRealThread GRealThread;
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struct _GRealThread
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{
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GThread thread;
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gint ref_count;
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gboolean ours;
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gchar *name;
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gpointer retval;
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};
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/* system thread implementation (gthread-posix.c, gthread-win32.c) */
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#if defined(HAVE_FUTEX) || defined(HAVE_FUTEX_TIME64)
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#include <errno.h>
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#include <linux/futex.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#ifndef FUTEX_WAIT_PRIVATE
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#define FUTEX_WAIT_PRIVATE FUTEX_WAIT
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#define FUTEX_WAKE_PRIVATE FUTEX_WAKE
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#endif
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/* Wrapper macro to call `futex_time64` and/or `futex` with simple
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* parameters and without returning the return value.
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*
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* We expect futex to sometimes return EAGAIN due to the race
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* between the caller checking the current value and deciding to
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* do the futex op. To avoid splattering errno on success, we
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* restore the original errno if EAGAIN is seen. See also:
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* https://gitlab.gnome.org/GNOME/glib/-/issues/3034
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*
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* If the `futex_time64` syscall does not exist (`ENOSYS`), we retry again
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* with the normal `futex` syscall. This can happen if newer kernel headers
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* are used than the kernel that is actually running.
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*
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* The `futex_time64` syscall is also skipped in favour of `futex` if the
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* Android runtime’s API level is lower than 30, as it’s blocked by seccomp
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* there and using it will cause the app to be terminated:
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* https://android-review.googlesource.com/c/platform/bionic/+/1094758
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* https://github.com/aosp-mirror/platform_bionic/commit/ee7bc3002dc3127faac110167d28912eb0e86a20
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*
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* This must not be called with a timeout parameter as that differs
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* in size between the two syscall variants!
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*/
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#if defined(HAVE_FUTEX) && defined(HAVE_FUTEX_TIME64)
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#if defined(__ANDROID__)
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#define g_futex_simple(uaddr, futex_op, ...) \
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G_STMT_START \
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{ \
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int saved_errno = errno; \
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int res = 0; \
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if (__builtin_available (android 30, *)) \
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{ \
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res = syscall (__NR_futex_time64, uaddr, (gsize) futex_op, __VA_ARGS__); \
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if (res < 0 && errno == ENOSYS) \
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{ \
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errno = saved_errno; \
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res = syscall (__NR_futex, uaddr, (gsize) futex_op, __VA_ARGS__); \
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} \
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} \
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else \
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{ \
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res = syscall (__NR_futex, uaddr, (gsize) futex_op, __VA_ARGS__); \
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} \
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if (res < 0 && errno == EAGAIN) \
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{ \
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errno = saved_errno; \
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} \
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} \
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G_STMT_END
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#else
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#define g_futex_simple(uaddr, futex_op, ...) \
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G_STMT_START \
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{ \
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int saved_errno = errno; \
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int res = syscall (__NR_futex_time64, uaddr, (gsize) futex_op, __VA_ARGS__); \
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if (res < 0 && errno == ENOSYS) \
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{ \
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errno = saved_errno; \
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res = syscall (__NR_futex, uaddr, (gsize) futex_op, __VA_ARGS__); \
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} \
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if (res < 0 && errno == EAGAIN) \
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{ \
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errno = saved_errno; \
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} \
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} \
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G_STMT_END
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#endif /* defined(__ANDROID__) */
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#elif defined(HAVE_FUTEX_TIME64)
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#define g_futex_simple(uaddr, futex_op, ...) \
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G_STMT_START \
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{ \
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int saved_errno = errno; \
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int res = syscall (__NR_futex_time64, uaddr, (gsize) futex_op, __VA_ARGS__); \
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if (res < 0 && errno == EAGAIN) \
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{ \
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errno = saved_errno; \
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} \
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} \
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G_STMT_END
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#elif defined(HAVE_FUTEX)
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#define g_futex_simple(uaddr, futex_op, ...) \
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G_STMT_START \
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{ \
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int saved_errno = errno; \
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int res = syscall (__NR_futex, uaddr, (gsize) futex_op, __VA_ARGS__); \
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if (res < 0 && errno == EAGAIN) \
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{ \
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errno = saved_errno; \
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} \
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} \
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G_STMT_END
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#else /* !defined(HAVE_FUTEX) && !defined(HAVE_FUTEX_TIME64) */
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#error "Neither __NR_futex nor __NR_futex_time64 are available"
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#endif /* defined(HAVE_FUTEX) && defined(HAVE_FUTEX_TIME64) */
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#endif
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void g_system_thread_wait (GRealThread *thread);
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GRealThread *g_system_thread_new (GThreadFunc proxy,
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gulong stack_size,
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const char *name,
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GThreadFunc func,
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gpointer data,
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GError **error);
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void g_system_thread_free (GRealThread *thread);
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G_NORETURN void g_system_thread_exit (void);
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void g_system_thread_set_name (const gchar *name);
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/* gthread.c */
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GThread *g_thread_new_internal (const gchar *name,
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GThreadFunc proxy,
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GThreadFunc func,
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gpointer data,
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gsize stack_size,
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GError **error);
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gpointer g_thread_proxy (gpointer thread);
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guint g_thread_n_created (void);
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gpointer g_private_set_alloc0 (GPrivate *key,
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gsize size);
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#endif /* __G_THREADPRIVATE_H__ */
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