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Diffstat (limited to 'REORG.TODO/sysdeps/powerpc/nptl/elide.h')
| -rw-r--r-- | REORG.TODO/sysdeps/powerpc/nptl/elide.h | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/powerpc/nptl/elide.h b/REORG.TODO/sysdeps/powerpc/nptl/elide.h new file mode 100644 index 0000000000..1c42814b71 --- /dev/null +++ b/REORG.TODO/sysdeps/powerpc/nptl/elide.h @@ -0,0 +1,125 @@ +/* elide.h: Generic lock elision support for powerpc. + Copyright (C) 2015-2017 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_PPC_H +# define ELIDE_PPC_H + +#ifdef ENABLE_LOCK_ELISION +# include <htm.h> +# include <elision-conf.h> + +/* Get the new value of adapt_count according to the elision + configurations. Returns true if the system should retry again or false + otherwise. */ +static inline bool +__get_new_count (uint8_t *adapt_count, int attempt) +{ + /* A persistent failure indicates that a retry will probably + result in another failure. Use normal locking now and + for the next couple of calls. */ + if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ())) + { + if (__elision_aconf.skip_lock_internal_abort > 0) + *adapt_count = __elision_aconf.skip_lock_internal_abort; + return false; + } + /* Same logic as above, but for a number of temporary failures in a + a row. */ + else if (attempt <= 1 && __elision_aconf.skip_lock_out_of_tbegin_retries > 0 + && __elision_aconf.try_tbegin > 0) + *adapt_count = __elision_aconf.skip_lock_out_of_tbegin_retries; + return true; +} + +/* CONCURRENCY NOTES: + + The evaluation of the macro expression is_lock_free encompasses one or + more loads from memory locations that are concurrently modified by other + threads. For lock elision to work, this evaluation and the rest of the + critical section protected by the lock must be atomic because an + execution with lock elision must be equivalent to an execution in which + the lock would have been actually acquired and released. Therefore, we + evaluate is_lock_free inside of the transaction that represents the + critical section for which we want to use lock elision, which ensures + the atomicity that we require. */ + +/* Returns 0 if the lock defined by is_lock_free was elided. + ADAPT_COUNT is a per-lock state variable. */ +# define ELIDE_LOCK(adapt_count, is_lock_free) \ + ({ \ + int ret = 0; \ + if (adapt_count > 0) \ + (adapt_count)--; \ + else \ + for (int i = __elision_aconf.try_tbegin; i > 0; i--) \ + { \ + if (__libc_tbegin (0)) \ + { \ + if (is_lock_free) \ + { \ + ret = 1; \ + break; \ + } \ + __libc_tabort (_ABORT_LOCK_BUSY); \ + } \ + else \ + if (!__get_new_count (&adapt_count,i)) \ + break; \ + } \ + ret; \ + }) + +# define ELIDE_TRYLOCK(adapt_count, is_lock_free, write) \ + ({ \ + int ret = 0; \ + if (__elision_aconf.try_tbegin > 0) \ + { \ + if (write) \ + __libc_tabort (_ABORT_NESTED_TRYLOCK); \ + ret = ELIDE_LOCK (adapt_count, is_lock_free); \ + } \ + ret; \ + }) + + +static inline bool +__elide_unlock (int is_lock_free) +{ + if (is_lock_free) + { + /* This code is expected to crash when trying to unlock a lock not + held by this thread. More information is available in the + __pthread_rwlock_unlock() implementation. */ + __libc_tend (0); + return true; + } + return false; +} + +# define ELIDE_UNLOCK(is_lock_free) \ + __elide_unlock (is_lock_free) + +# else + +# define ELIDE_LOCK(adapt_count, is_lock_free) 0 +# define ELIDE_TRYLOCK(adapt_count, is_lock_free, write) 0 +# define ELIDE_UNLOCK(is_lock_free) 0 + +#endif /* ENABLE_LOCK_ELISION */ + +#endif |