new file mode 100644
@@ -0,0 +1,55 @@
+/* Out-of-line notification function for the GSCOPE locking mechanism.
+ Copyright (C) 2007-2021 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <ldsodefs.h>
+#include <pthread.h>
+#include <htl/pt-internal.h>
+
+void
+__thread_gscope_wait (void)
+{
+ size_t i;
+ struct __pthread *t;
+ int *gscope_flagp;
+
+ lll_lock (GL (dl_pthread_threads_lock), LLL_PRIVATE);
+
+ /* Iterate over the list of threads. */
+ for (i = 0; i < GL (dl_pthread_num_threads); ++i)
+ {
+ t = GL (dl_pthread_threads[i]);
+ if (t == NULL || t->tcb->gscope_flag == THREAD_GSCOPE_FLAG_UNUSED)
+ continue;
+
+ gscope_flagp = &t->tcb->gscope_flag;
+
+ /* We have to wait until this thread is done with the global
+ scope. First tell the thread that we are waiting and
+ possibly have to be woken. */
+ if (atomic_compare_and_exchange_bool_acq (gscope_flagp,
+ THREAD_GSCOPE_FLAG_WAIT,
+ THREAD_GSCOPE_FLAG_USED))
+ continue;
+
+ do
+ lll_wait (gscope_flagp, THREAD_GSCOPE_FLAG_WAIT, LLL_PRIVATE);
+ while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
+ }
+
+ lll_unlock (GL (dl_pthread_threads_lock), LLL_PRIVATE);
+}
@@ -369,6 +369,27 @@ _hurd_tls_new (thread_t child, struct i386_thread_state *state, tcbhead_t *tcb)
return err;
}
+/* Global scope switch support. */
+# define THREAD_GSCOPE_IN_TCB 1
+
+# define THREAD_GSCOPE_FLAG_UNUSED 0
+# define THREAD_GSCOPE_FLAG_USED 1
+# define THREAD_GSCOPE_FLAG_WAIT 2
+
+# define THREAD_GSCOPE_SET_FLAG() \
+ THREAD_SETMEM (THREAD_SELF, gscope_flag, THREAD_GSCOPE_FLAG_USED)
+
+# define THREAD_GSCOPE_RESET_FLAG() \
+ ({ \
+ int __flag; \
+ asm volatile ("xchgl %0, %%gs:%P1" \
+ : "=r" (__flag) \
+ : "i" (offsetof (tcbhead_t, gscope_flag)), \
+ "0" (THREAD_GSCOPE_FLAG_UNUSED)); \
+ if (__flag == THREAD_GSCOPE_FLAG_WAIT) \
+ lll_wake (THREAD_SELF->gscope_flag, LLL_PRIVATE); \
+ })
+
#endif /* !__ASSEMBLER__ */
#endif /* i386/tls.h */
@@ -52,26 +52,6 @@
# define GET_DTV(descr) \
(((tcbhead_t *) (descr))->dtv)
-/* Global scope switch support. */
-#define THREAD_GSCOPE_IN_TCB 0
-#define THREAD_GSCOPE_GLOBAL
-#define THREAD_GSCOPE_SET_FLAG() \
- atomic_exchange_and_add_acq (&GL(dl_thread_gscope_count), 1)
-#define THREAD_GSCOPE_RESET_FLAG() \
- do \
- if (atomic_exchange_and_add_rel (&GL(dl_thread_gscope_count), -1) == 1) \
- lll_wake (GL(dl_thread_gscope_count), 0); \
- while (0)
-#define THREAD_GSCOPE_WAIT() \
- do \
- { \
- int count; \
- atomic_write_barrier (); \
- while ((count = GL(dl_thread_gscope_count))) \
- lll_wait (GL(dl_thread_gscope_count), count, 0); \
- } \
- while (0)
-
#endif /* !ASSEMBLER */
This is a new implementation of GSCOPE which largely mirrors its NPTL counterpart. Same as in NPTL, instead of a global flag shared between threads, there is now a per-thread GSCOPE flag stored in each thread's TCB. This makes entering and exiting a GSCOPE faster at the expense of making THREAD_GSCOPE_WAIT () slower. The largest win is the elimination of many redundant gsync_wake () RPC calls; previously, even simplest programs would make dozens of fully redundant gsync_wake () calls. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> --- sysdeps/htl/dl-thread_gscope_wait.c | 55 +++++++++++++++++++++++++++++ sysdeps/mach/hurd/i386/tls.h | 21 +++++++++++ sysdeps/mach/hurd/tls.h | 20 ----------- 3 files changed, 76 insertions(+), 20 deletions(-) create mode 100644 sysdeps/htl/dl-thread_gscope_wait.c