diff options
Diffstat (limited to 'sysdeps/powerpc/nptl/elide.h')
| -rw-r--r-- | sysdeps/powerpc/nptl/elide.h | 119 |
1 files changed, 65 insertions, 54 deletions
diff --git a/sysdeps/powerpc/nptl/elide.h b/sysdeps/powerpc/nptl/elide.h index 389f5a5e9e..77bd82ecba 100644 --- a/sysdeps/powerpc/nptl/elide.h +++ b/sysdeps/powerpc/nptl/elide.h @@ -1,5 +1,5 @@ /* elide.h: Generic lock elision support for powerpc. - Copyright (C) 2015 Free Software Foundation, Inc. + Copyright (C) 2015-2016 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 @@ -23,67 +23,78 @@ # include <htm.h> # include <elision-conf.h> -/* Returns true if the lock defined by is_lock_free as elided. - ADAPT_COUNT is a pointer to per-lock state variable. */ - +/* 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 -__elide_lock (uint8_t *adapt_count, int is_lock_free) +__get_new_count (uint8_t *adapt_count, int attempt) { - if (*adapt_count > 0) + /* 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 ())) { - (*adapt_count)--; + if (__elision_aconf.skip_lock_internal_abort > 0) + *adapt_count = __elision_aconf.skip_lock_internal_abort; return false; } - - for (int i = __elision_aconf.try_tbegin; i > 0; i--) - { - if (__builtin_tbegin (0)) - { - if (is_lock_free) - return true; - /* Lock was busy. */ - __builtin_tabort (_ABORT_LOCK_BUSY); - } - else - { - /* 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; - break; - } - /* Same logic as above, but for a number of temporary failures in a - a row. */ - else if (__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 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; } -# define ELIDE_LOCK(adapt_count, is_lock_free) \ - __elide_lock (&(adapt_count), is_lock_free) - - -static inline bool -__elide_trylock (uint8_t *adapt_count, int is_lock_free, int write) -{ - if (__elision_aconf.try_tbegin > 0) - { - if (write) - __builtin_tabort (_ABORT_NESTED_TRYLOCK); - return __elide_lock (adapt_count, is_lock_free); - } - return false; -} +/* 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) \ - __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 @@ -91,7 +102,7 @@ __elide_unlock (int is_lock_free) { if (is_lock_free) { - __builtin_tend (0); + __libc_tend (0); return true; } return false; |