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-rw-r--r--sysdeps/tile/nptl/pthread_spin_lock.c56
1 files changed, 56 insertions, 0 deletions
diff --git a/sysdeps/tile/nptl/pthread_spin_lock.c b/sysdeps/tile/nptl/pthread_spin_lock.c
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+/* Copyright (C) 2011-2014 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
+
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+#include "pthreadP.h"
+#include <arch/spr_def.h>
+#include <atomic.h>
+
+/* Bound point for bounded exponential backoff */
+#define BACKOFF_MAX 2048
+
+/* Initial cycle delay for exponential backoff */
+#define BACKOFF_START 32
+
+#ifdef __tilegx__
+/* Use cmpexch() after the initial fast-path exch to avoid
+ invalidating the cache line of the lock holder. */
+# define TNS(p) atomic_exchange_acq((p), 1)
+# define CMPTNS(p) atomic_compare_and_exchange_val_acq((p), 1, 0)
+#else
+# define TNS(p) __insn_tns(p)
+# define CMPTNS(p) __insn_tns(p)
+# define SPR_CYCLE SPR_CYCLE_LOW /* The low 32 bits are sufficient. */
+#endif
+
+int
+pthread_spin_lock (pthread_spinlock_t *lock)
+{
+ if (__builtin_expect (TNS (lock) != 0, 0))
+ {
+ unsigned int backoff = BACKOFF_START;
+ while (CMPTNS (lock) != 0)
+ {
+ unsigned int start = __insn_mfspr (SPR_CYCLE);
+ while (__insn_mfspr (SPR_CYCLE) - start < backoff)
+ ;
+ if (backoff < BACKOFF_MAX)
+ backoff *= 2;
+ }
+ }
+ return 0;
+}