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Diffstat (limited to 'REORG.TODO/sysdeps/x86/elide.h')
| -rw-r--r-- | REORG.TODO/sysdeps/x86/elide.h | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/x86/elide.h b/REORG.TODO/sysdeps/x86/elide.h new file mode 100644 index 0000000000..53de41836e --- /dev/null +++ b/REORG.TODO/sysdeps/x86/elide.h @@ -0,0 +1,119 @@ +/* elide.h: Generic lock elision support. + Copyright (C) 2014-2017 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 + <http://www.gnu.org/licenses/>. */ +#ifndef ELIDE_H +#define ELIDE_H 1 + +#include <hle.h> +#include <elision-conf.h> +#include <atomic.h> + + +/* Adapt elision with ADAPT_COUNT and STATUS and decide retries. */ + +static inline bool +elision_adapt(signed char *adapt_count, unsigned int status) +{ + if (status & _XABORT_RETRY) + return false; + if ((status & _XABORT_EXPLICIT) + && _XABORT_CODE (status) == _ABORT_LOCK_BUSY) + { + /* Right now we skip here. Better would be to wait a bit + and retry. This likely needs some spinning. Be careful + to avoid writing the lock. + Using relaxed MO and separate atomic accesses is sufficient because + adapt_count is just a hint. */ + if (atomic_load_relaxed (adapt_count) != __elision_aconf.skip_lock_busy) + atomic_store_relaxed (adapt_count, __elision_aconf.skip_lock_busy); + } + /* Internal abort. There is no chance for retry. + Use the normal locking and next time use lock. + Be careful to avoid writing to the lock. See above for MO. */ + else if (atomic_load_relaxed (adapt_count) + != __elision_aconf.skip_lock_internal_abort) + atomic_store_relaxed (adapt_count, + __elision_aconf.skip_lock_internal_abort); + return true; +} + +/* is_lock_free must be executed inside the transaction */ + +/* Returns true if lock defined by IS_LOCK_FREE was elided. + ADAPT_COUNT is a per-lock state variable; it must be accessed atomically + to avoid data races but is just a hint, so using relaxed MO and separate + atomic loads and stores instead of atomic read-modify-write operations is + sufficient. */ + +#define ELIDE_LOCK(adapt_count, is_lock_free) \ + ({ \ + int ret = 0; \ + \ + if (atomic_load_relaxed (&(adapt_count)) <= 0) \ + { \ + for (int i = __elision_aconf.retry_try_xbegin; i > 0; i--) \ + { \ + unsigned int status; \ + if ((status = _xbegin ()) == _XBEGIN_STARTED) \ + { \ + if (is_lock_free) \ + { \ + ret = 1; \ + break; \ + } \ + _xabort (_ABORT_LOCK_BUSY); \ + } \ + if (!elision_adapt (&(adapt_count), status)) \ + break; \ + } \ + } \ + else \ + atomic_store_relaxed (&(adapt_count), \ + atomic_load_relaxed (&(adapt_count)) - 1); \ + ret; \ + }) + +/* Returns true if lock defined by IS_LOCK_FREE was try-elided. + ADAPT_COUNT is a per-lock state variable. */ + +#define ELIDE_TRYLOCK(adapt_count, is_lock_free, write) ({ \ + int ret = 0; \ + if (__elision_aconf.retry_try_xbegin > 0) \ + { \ + if (write) \ + _xabort (_ABORT_NESTED_TRYLOCK); \ + ret = ELIDE_LOCK (adapt_count, is_lock_free); \ + } \ + ret; \ + }) + +/* Returns true if lock defined by IS_LOCK_FREE was elided. The call + to _xend crashes if the application incorrectly tries to unlock a + lock which has not been locked. */ + +#define ELIDE_UNLOCK(is_lock_free) \ + ({ \ + int ret = 0; \ + if (is_lock_free) \ + { \ + _xend (); \ + ret = 1; \ + } \ + ret; \ + }) + +#endif |